@article{simpson_krissanaprasit_chester_koehler_labean_brown_2024, title={Utilizing multiscale engineered biomaterials to examine TGF-β-mediated myofibroblastic differentiation}, ISSN={["1524-475X"]}, DOI={10.1111/wrr.13168}, abstractNote={Cells integrate many mechanical and chemical cues to drive cell signalling responses. Because of the complex nature and interdependency of alterations in extracellular matrix (ECM) composition, ligand density, mechanics, and cellular responses it is difficult to tease out individual and combinatorial contributions of these various factors in driving cell behavior in homeostasis and disease. Tuning of material viscous and elastic properties, and ligand densities, in combinatorial fashions would enhance our understanding of how cells process complex signals. For example, it is known that increased ECM mechanics and transforming growth factor beta (TGF-β) receptor (TGF-β-R) spacing/clustering independently drive TGF-β signalling and associated myofibroblastic differentiation. However, it remains unknown how these inputs orthogonally contribute to cellular outcomes. Here, we describe the development of a novel material platform that combines microgel thin films with controllable viscoelastic properties and DNA origami to probe how viscoelastic properties and nanoscale spacing of TGF-β-Rs contribute to TGF-β signalling and myofibroblastic differentiation. We found that highly viscous materials with non-fixed TGF-β-R spacing promoted increased TGF-β signalling and myofibroblastic differentiation. This is likely due to the ability of cells to better cluster receptors on these surfaces. These results provide insight into the contribution of substrate properties and receptor localisation on downstream signalling. Future studies allow for exploration into other receptor-mediated processes.}, journal={WOUND REPAIR AND REGENERATION}, author={Simpson, Aryssa and Krissanaprasit, Abhichart and Chester, Daniel and Koehler, Cynthia and Labean, Thomas H. and Brown, Ashley C.}, year={2024}, month={Mar} }
 @article{zhang_scull_gluck_brown_king_2023, title={Effects of sterilization methods on gelatin methacryloyl hydrogel properties and macrophage gene expression in vitro}, volume={18}, ISSN={["1748-605X"]}, url={https://doi.org/10.1088/1748-605X/aca4b2}, DOI={10.1088/1748-605X/aca4b2}, abstractNote={To assure the long-term safety and functional performance after implantation, it is of critical importance to completely sterilize a biomaterial implant. Ineffective sterilization can cause severe inflammation and infection at the implant site, leading to detrimental events of morbidity and even mortality. Macrophages are pivotal players in the inflammatory and foreign body response after implanting a biomaterial in the body. However, the relationship between the sterilization procedure and macrophage response has not been established. In this study, three commonly used sterilization methods, including autoclaving, ethylene oxide gas and ethanol treatment, were used to sterilize a gelatin methacryloyl hydrogel. The impacts of different sterilization methods on the structure and physical properties of the hydrogel were compared. Macrophage responses to the sterilized hydrogel were analyzed based on their morphology, viability and in vitro gene expression. It was found that the sterilization methods only marginally altered the hydrogel morphology, swelling behavior and elastic modulus, but significantly impacted macrophage gene expression within 48 h and over 7 d in vitro. Therefore, when selecting sterilization methods for GelMA hydrogel, not only the sterility and hydrogel properties, such as material destruction and degradation caused by temperature and moisture, should be taken into consideration, but also the cellular responses to the sterilized material which could be substantially different.}, number={1}, journal={BIOMEDICAL MATERIALS}, author={Zhang, Fan and Scull, Grant and Gluck, Jessica M. and Brown, Ashley C. and King, Martin W.}, year={2023}, month={Jan} }
 @article{zhang_gluck_brown_zaharoff_king_2023, title={Heparin Affinity-Based IL-4 Delivery to Modulate Macrophage Phenotype and Endothelial Cell Activity In Vitro}, volume={15}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.3c00489}, DOI={10.1021/acsami.3c00489}, abstractNote={Macrophages play a pivotal role in wound healing and tissue regeneration, as they are rapidly recruited to the site of injury or implanted foreign material. Depending on their interaction with the material, macrophages can develop different phenotypes, with the M1 pro-inflammatory and M2 pro-regenerative phenotypes being highly involved in tissue regeneration. M2 macrophages mitigate inflammation and promote tissue regeneration and extracellular matrix remodeling. In this study, we engineered a gelatin-heparin-methacrylate (GelMA-HepMA) hydrogel that gradually releases interleukin-4 (IL-4), a cytokine that modulates macrophages to adopt the M2 phenotype. Methacrylation of heparin improved the retention of both heparin and IL-4 within the hydrogel. The GelMA-HepMA hydrogel and IL-4 synergistically downregulated M1 gene expression and upregulated M2 gene expression in macrophages within 48 h of in vitro cell culture. However, the M2-like macrophage phenotype induced by the GelMA-HepMA-IL-4 hydrogel did not necessarily further improve endothelial cell proliferation and migration in vitro.}, number={23}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Zhang, Fan and Gluck, Jessica M. and Brown, Ashley C. and Zaharoff, David A. and King, Martin W.}, year={2023}, month={Jun}, pages={27457–27470} }
 @article{moiseiwitsch_nellenbach_downey_boorman_brown_guzzetta_2023, title={Influence of Fibrinogen Concentrate on Neonatal Clot Structure When Administered Ex Vivo After Cardiopulmonary Bypass}, volume={137}, ISSN={["0003-2999"]}, DOI={10.1213/ANE.0000000000006357}, abstractNote={BACKGROUND: Bleeding is a serious complication of cardiopulmonary bypass (CPB) in neonates. Blood product transfusions are often needed to adequately restore hemostasis, but are associated with significant risks. Thus, neonates would benefit from other effective, and safe, hemostatic therapies. The use of fibrinogen concentrate (FC; RiaSTAP, CSL Behring, Marburg, Germany) is growing in popularity, but has not been adequately studied in neonates. Here, we characterize structural and degradation effects on the neonatal fibrin network when FC is added ex vivo to plasma obtained after CPB. METHODS: After approval by the institutional review board and parental consent, blood samples were collected from neonates undergoing cardiac surgery and centrifuged to yield platelet poor plasma. Clots were formed ex vivo from plasma obtained at several time points: (1) baseline, (2) immediately post-CPB, and (3) post-transfusion of cryoprecipitate. In addition, we utilized post-CPB plasma to construct the following conditions: (4) post-CPB +0.5 mg/mL FC, and (5) post-CPB +0.9 mg/mL FC. The resultant fibrin networks were imaged using confocal microscopy to analyze overall structure, fiber density, and alignment. Clots were also analyzed using a microfluidic degradation assay. Fibrinogen content was quantified for all plasma samples. RESULTS: The addition of 0.5 or 0.9 mg/mL FC to post-CPB samples significantly enhanced the median fiber density when compared to untreated post-CPB samples (post-CPB = 0.44 [interquartile range {IQR}: 0.36–0.52], post-CPB +0.5 mg/mL FC = 0.69 [0.56–0.77], post-CPB +0.9 mg/mL FC = 0.87 [0.59–0.96]; P = .01 and P = .006, respectively). The addition of 0.9 mg/mL FC to post-CPB samples resulted in a greater fiber density than that observed after the in vivo transfusion of cryoprecipitate (post-transfusion = 0.54 [0.45–0.77], post-CPB +0.9 mg/mL FC = 0.87 [0.59–0.96]; P = .002). Median fiber alignment did not differ significantly between post-CPB samples and samples treated with FC. Degradation rates were not statistically significant from baseline values with either 0.5 or 0.9 mg/mL FC. In addition, we found a significant correlation between the difference in the baseline and post-CPB fibrinogen concentration with patient age (P = .033) after controlling for weight. CONCLUSIONS: Our results show that clots formed ex vivo with clinically relevant doses of FC (0.9 mg/mL) display similar structural and degradation characteristics compared to the in vivo transfusion of cryoprecipitate. These findings suggest that FC is effective in restoring structural fibrin clot properties after CPB. Future studies after the administration of FC in vivo are needed to validate this hypothesis.}, number={3}, journal={ANESTHESIA AND ANALGESIA}, author={Moiseiwitsch, Nina and Nellenbach, Kimberly A. and Downey, Laura A. and Boorman, David and Brown, Ashley C. and Guzzetta, Nina A.}, year={2023}, month={Sep}, pages={682–690} }
 @article{tigner_scull_brown_alge_2023, title={Microparticle Hydrogel Material Properties Emerge from Mixing-Induced Homogenization in a Poly(ethylene glycol) and Dextran Aqueous Two-Phase System}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.3c00557}, abstractNote={Polymer–polymer aqueous two-phase systems (ATPSs) are attractive for microgel synthesis, but given the complexity of phase separation, predicting microgel material properties from ATPS formulations is not trivial. The objective of this study was to determine how the phase diagram of a poly(ethylene glycol) (PEG) and dextran ATPS is related to the material properties of PEG microgel products. PEG-dextran ATPSs were prepared from four-arm 20 kDa PEG-norbornene and 40 kDa dextran in phosphate buffered saline (PBS), and the phase diagram was constructed. PEG microgels were synthesized from five ATPS formulations using an oligopeptide cross-linker and thiol-norbornene photochemistry. Thermogravimetric analysis (TGA) revealed that the polymer concentration of microgel pellets linearly correlates with the average concentration of PEG in the ATPS rather than the separated phase compositions, as determined from the phase diagram. Atomic force microscopy (AFM) and bulk rheology studies demonstrated that the mechanical properties of microgels rely on both the average concentration of PEG in the ATPS and the ATPS volume ratio as determined from the phase diagram. These findings suggest that PEG-dextran ATPSs undergo homogenization upon mixing, which principally determines the material properties of the microgels upon gelation.}, journal={MACROMOLECULES}, author={Tigner, Thomas J. and Scull, Grant and Brown, Ashley C. and Alge, Daniel L.}, year={2023}, month={Oct} }
 @article{prodromou_moore_chu_deal_san miguel_brown_daniele_pozdin_menegatti_2023, title={Molecular Engineering of Cyclic Azobenzene-Peptide Hybrid Ligands for the Purification of Human Blood Factor VIII via Photo-Affinity Chromatography}, volume={1}, ISSN={["1616-3028"]}, url={http://dx.doi.org/10.1002/adfm.202213881}, DOI={10.1002/adfm.202213881}, abstractNote={The use of benign stimuli to control the binding and release of labile biologics for their isolation from complex feedstocks is a key goal of modern biopharmaceutical technology. This study introduces cyclic azobenzene‐peptide (CAP) ligands for the rapid and discrete photo‐responsive capture and release of blood coagulation factor VIII (FVIII). A predictive method—based on amino acid sequence and molecular architecture of CAPs—is developed to correlate the conformation of cis/trans‐CAP photo‐isomers to FVIII binding and release. Combined in silico ‐ in vitro analysis of FVIII:peptide interactions guide the design of a rational approach to optimize isomerization kinetics and biorecognition of CAPs. A photoaffinity adsorbent, prepared by conjugating selected CAP G‐cycloAZOB[Lys‐YYKHLYN‐Lys]‐G on translucent chromatographic beads, features high binding capacity (>6 mg of FVIII per mL of resin) and rapid photo‐isomerization kinetics (τ < 30 s) when exposed to 420–450 nm light at the intensity of 0.1 W cm−2. The adsorbent purifies FVIII from a recombinant harvest using a single mobile phase, affording high product yield (>90%), purity (>95%), and blood clotting activity. The CAPs introduced in this report demonstrate a novel route integrating gentle operational conditions in a rapid and efficient bioprocess for the purification of life‐saving biotherapeutics.}, journal={ADVANCED FUNCTIONAL MATERIALS}, publisher={Wiley}, author={Prodromou, Raphael and Moore, Brandyn David and Chu, Wenning and Deal, Halston and San Miguel, Adriana and Brown, Ashley Carson and Daniele, Michael Angelo-Anthony and Pozdin, Vladimir Aleksandrovich and Menegatti, Stefano}, year={2023}, month={Jan} }
 @misc{sheridan_brown_2023, title={Recent Advances in Blood Cell-Inspired and Clot-Targeted Thrombolytic Therapies}, volume={2023}, ISSN={["1932-7005"]}, DOI={10.1155/2023/6117810}, abstractNote={Myocardial infarction, stroke, and pulmonary embolism are all deadly conditions associated with excessive thrombus formation. Standard treatment for these conditions involves systemic delivery of thrombolytic agents to break up clots and restore blood flow; however, this treatment can impact the hemostatic balance in other parts of the vasculature, which can lead to excessive bleeding. To avoid this potential danger, targeted thrombolytic treatments that can successfully target thrombi and release an effective therapeutic load are necessary. Because activated platelets and fibrin make up a large proportion of clots, these two components provide ample opportunities for targeting. This review will highlight potential thrombus targeting mechanisms as well as recent advances in thrombolytic therapies which utilize blood-cells and clotting proteins to effectively target and lyse clots.}, journal={JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE}, author={Sheridan, Anastasia and Brown, Ashley C.}, year={2023}, month={Feb} }
 @article{chee_mihalko_nellenbach_sollinger_huang_hon_pandit_cheng_brown_2023, title={Wound-triggered shape change microgels for the development of enhanced biomimetic function platelet-like particles}, volume={10}, ISSN={["1552-4965"]}, DOI={10.1002/jbm.a.37625}, abstractNote={Platelets play a pivotal role in hemostasis and wound healing and conditional shape change is an important component of platelet functionality. In normal circumstances, platelets travel through the circulatory system in an inactive rounded state, which enables platelets to easily move to vessel walls for attachment. When an injury occurs, platelets are prompted by molecules, such as thrombin, to shift into a stellate shape and increase exposure of fibrin-binding receptors. When active, platelets promote hemostasis and clot retraction, which enhances clot stability and promotes healing. However, in conditions where platelets are depleted or hyporeactive, these functions are diminished and lead to inhibited hemostasis and healing. To treat platelet depletion, our group developed platelet-like particles (PLPs) which consist of highly deformable microgels coupled to fibrin binding motif. However, first generation PLPs do not exhibit wound-triggered shape change like native platelets. Thus, the objective of these studies was to develop a PLP formulation that changes shape when prompted by thrombin. To create thrombin-sensitive PLPs (TS-PLPs), we incorporated a thrombin-cleavable peptide into the microgel body and then evaluated PLP properties before and after exposure to thrombin including morphology, size, and in vitro clot retraction. Once thrombin-prompted shape change ability was confirmed, the TS-PLPs were tested in vivo for hemostatic ability and subsequent wound healing outcomes in a murine liver trauma model. We found that TS-PLPs exhibit a wound-triggered shape change, induce significant clot retraction following exposure to thrombin and promote hemostasis and healing in vivo after trauma.}, journal={JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A}, author={Chee, Eunice and Mihalko, Emily and Nellenbach, Kimberly and Sollinger, Jennifer and Huang, Ke and Hon, Mason and Pandit, Sanika and Cheng, Ke and Brown, Ashley}, year={2023}, month={Oct} }
 @article{londono-zuluaga_jameel_gonzalez_nellenbach_brown_yang_lucia_2022, title={A Unique Crustacean-Based Chitin Platform to Reduce Self-Aggregation of Polysaccharide Nanofibers}, volume={10}, ISSN={["2079-6439"]}, url={https://www.mdpi.com/2079-6439/10/10/87}, DOI={10.3390/fib10100087}, abstractNote={Every year, over 8 million tons of crustacean shells are discarded. However, there exists an opportunity for valorizing the chitin and calcium carbonate part of the composition of the shells. Our study revealed crustacean chitin reduces self-aggregation effects. It was shown that crustacean-based nanofibers alone or added to cellulose offer unprecedented reductions in viscosity even after drying to produce foams impossible for cellulose. Polysaccharide nanofibers suffer from increased viscosity from strong hydrogen bonding addressed by the incorporation of crustacean-based nanofibers. The ability of the nanocomposite to overcome self-aggregation and collapse was attributed to organized chitin nanofiber morphology in the crustacean matrix. As a result of enhanced surface area from reduced fiber aggregation, the chitin/crustacean-cellulose blend was tested for a biomedical application requiring a high surface area: coagulation. Preliminary experiments showed the crustacean matrices, especially those containing calcium carbonate, induced blood clotting when 35 s. A materials platform is proposed for bio-based nanofiber production overcoming intractable and difficult-to-address self-aggregation effects associated with polysaccharides.}, number={10}, journal={FIBERS}, author={Londono-Zuluaga, Carolina and Jameel, Hasan and Gonzalez, Ronalds and Nellenbach, Kimberly and Brown, Ashley and Yang, Guihua and Lucia, Lucian}, year={2022}, month={Oct} }
 @misc{simpson_shukla_brown_2022, title={Biomaterials for Hemostasis}, volume={24}, ISSN={["1545-4274"]}, DOI={10.1146/annurev-bioeng-012521-101942}, abstractNote={Uncontrolled bleeding is a major problem in trauma and emergency medicine. While materials for trauma applications would certainly find utility in traditional surgical settings, the unique environment of emergency medicine introduces additional design considerations, including the need for materials that are easily deployed in austere environments. Ideally, these materials would be available off the shelf, could be easily transported, and would be able to be stored at room temperature for some amount of time. Both natural and synthetic materials have been explored for the development of hemostatic materials. This review article provides an overview of classes of materials used for topical hemostats and newer developments in the area of injectable hemostats for use in emergency medicine. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.}, journal={ANNUAL REVIEW OF BIOMEDICAL ENGINEERING}, author={Simpson, Aryssa and Shukla, Anita and Brown, Ashley C.}, year={2022}, pages={111–135} }
 @article{moiseiwitsch_zwennes_szlam_sniecinski_brown_2022, title={COVID-19 patient fibrinogen produces dense clots with altered polymerization kinetics, partially explained by increased sialic acid}, ISSN={["1538-7836"]}, DOI={10.1111/jth.15882}, abstractNote={Thrombogenicity is a known complication of COVID‐19, resulting from SARS‐CoV‐2 infection, with significant effects on morbidity and mortality.}, journal={JOURNAL OF THROMBOSIS AND HAEMOSTASIS}, author={Moiseiwitsch, Nina and Zwennes, Nicole and Szlam, Fania and Sniecinski, Roman and Brown, Ashley}, year={2022}, month={Oct} }
 @article{chester_lee_wagner_nordberg_fisher_brown_2022, title={Elucidating the combinatorial effect of substrate stiffness and surface viscoelasticity on cellular phenotype}, ISSN={["1552-4965"]}, DOI={10.1002/jbm.a.37367}, abstractNote={Abstract Cells maintain tensional homeostasis by monitoring the mechanics of their microenvironment. In order to understand this mechanotransduction phenomenon, hydrogel materials have been developed with either controllable linear elastic or viscoelastic properties. Native biological tissues, and biomaterials used for medical purposes, often have complex mechanical properties. However, due to the difficulty in completely decoupling the elastic and viscous components of hydrogel materials, the effect of complex composite materials on cellular responses has largely gone unreported. Here, we characterize a novel composite hydrogel system capable of decoupling and individually controlling both the bulk stiffness and surface viscoelasticity of the material by combining polyacrylamide (PA) gels with microgel thin films. By taking advantage of the high degree of control over stiffness offered by PA gels and viscoelasticity, in terms of surface loss tangent, of microgel thin films, it is possible to study the influence that bulk substrate stiffness and surface loss tangent have on complex fibroblast responses, including cellular and nuclear morphology and gene expression. This material system provides a facile method for investigating cellular responses to complex material mechanics with great precision and allows for a greater understanding of cellular mechanotransduction mechanisms than previously possible through current model material platforms.}, journal={JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A}, author={Chester, Daniel and Lee, Veronica and Wagner, Paul and Nordberg, Matthew and Fisher, Matthew B. and Brown, Ashley C.}, year={2022}, month={Feb} }
 @article{popowski_moatti_scull_silkstone_lutz_lópez de juan abad_george_belcher_zhu_mei_et al._2022, title={Inhalable dry powder mRNA vaccines based on extracellular vesicles}, volume={5}, ISSN={2590-2385}, url={http://dx.doi.org/10.1016/j.matt.2022.06.012}, DOI={10.1016/j.matt.2022.06.012}, abstractNote={Respiratory diseases are a global burden, with millions of deaths attributed to pulmonary illnesses and dysfunctions. Therapeutics have been developed, but they present major limitations regarding pulmonary bioavailability and product stability. To circumvent such limitations, we developed room-temperature-stable inhalable lung-derived extracellular vesicles or exosomes (Lung-Exos) as mRNA and protein drug carriers. Compared with standard synthetic nanoparticle liposomes (Lipos), Lung-Exos exhibited superior distribution to the bronchioles and parenchyma and are deliverable to the lungs of rodents and nonhuman primates (NHPs) by dry powder inhalation. In a vaccine application, severe acute respiratory coronavirus 2 (SARS-CoV-2) spike (S) protein encoding mRNA-loaded Lung-Exos (S-Exos) elicited greater immunoglobulin G (IgG) and secretory IgA (SIgA) responses than its loaded liposome (S-Lipo) counterpart. Importantly, S-Exos remained functional at room-temperature storage for one month. Our results suggest that extracellular vesicles can serve as an inhaled mRNA drug-delivery system that is superior to synthetic liposomes.}, number={9}, journal={Matter}, publisher={Elsevier BV}, author={Popowski, Kristen D. and Moatti, Adele and Scull, Grant and Silkstone, Dylan and Lutz, Halle and López de Juan Abad, Blanca and George, Arianna and Belcher, Elizabeth and Zhu, Dashuai and Mei, Xuan and et al.}, year={2022}, month={Sep}, pages={2960–2974} }
 @article{wang_sun_vallabhuneni_pawlowski_vahabi_nellenbach_brown_scholle_zhao_kota_2022, title={On-demand, remote and lossless manipulation of biofluid droplets}, ISSN={["2051-6355"]}, DOI={10.1039/d2mh00695b}, abstractNote={The recent global outbreaks of epidemics and pandemics have shown us that we are severely under-prepared to cope with infectious agents. Exposure to infectious agents present in biofluids (e.g., blood, saliva, urine etc.) poses a severe risk to clinical laboratory personnel and healthcare workers, resulting in hundreds of millions of hospital-acquired and laboratory-acquired infections annually. Novel technologies that can minimize human exposure through remote and automated handling of infectious biofluids will mitigate such risk. In this work, we present biofluid manipulators, which allow on-demand, remote and lossless manipulation of virtually any liquid droplet. Our manipulators are designed by integrating thermo-responsive soft actuators with superomniphobic surfaces. Utilizing our manipulators, we demonstrate on-demand, remote and lossless manipulation of biofluid droplets. We envision that our biofluid manipulators will not only reduce manual operations and minimize exposure to infectious agents, but also pave the way for developing inexpensive, simple and portable robotic systems, which can allow point-of-care operations, particularly in developing nations.}, journal={MATERIALS HORIZONS}, author={Wang, Wei and Sun, Jiefeng and Vallabhuneni, Sravanthi and Pawlowski, Benjamin and Vahabi, Hamed and Nellenbach, Kimberly and Brown, Ashley C. and Scholle, Frank and Zhao, Jianguo and Kota, Arun K.}, year={2022}, month={Sep} }
 @article{wang_hamedi_zhang_el-shafei_brown_gluck_king_2022, title={Plasma-Induced Diallyldimethylammonium Chloride Antibacterial Hernia Mesh}, volume={11}, ISSN={["2576-6422"]}, url={https://doi.org/10.1021/acsabm.2c00695}, DOI={10.1021/acsabm.2c00695}, abstractNote={A hernia is a pathological condition caused by a defect or opening in the muscle wall, which leads to organs pushing through the opening or defect. Hernia recurrence, seroma, persistent pain, tissue adhesions, and wound infection are common complications following hernia repair surgery. Infection after hernia mesh implantation is the third major complication leading to hernia recurrence. In order to reduce the incidence of late infections, we developed a polypropylene mesh with antibacterial properties. In this study, knitted polypropylene meshes were exposed to radio-frequency plasma to activate their surfaces. The antibacterial monomer diallyldimethylammonium chloride (DADMAC) was then grafted onto the mesh surface using pentaerythritol tetraacrylate as the cross-linker since it is able to engage all four functional groups to form a high-density cross-linked network. The subsequent antibacterial performance showed a 2.9 log reduction toward Staphylococcus aureus and a 0.9 log reduction for Escherichia coli.}, journal={ACS APPLIED BIO MATERIALS}, author={Wang, Ziyu and Hamedi, Hamid and Zhang, Fan and El-Shafei, Ahmed and Brown, Ashley C. and Gluck, Jessica M. and King, Martin W.}, year={2022}, month={Nov} }
 @article{nellenbach_brown_2022, title={Platelet-mimicking procoagulant nanoparticles: Potential strategies for mitigating blood shortages}, ISSN={["1538-7836"]}, DOI={10.1111/jth.15720}, abstractNote={Bleeding can be a lifethreating event following trauma or surgery. Many factors can increase a patient's likelihood of severe bleeding, including the use of anticoagulants or having hereditary clotting disorders or thrombocytopenia. In a hospital setting, transfusion of donor blood products, including red blood cells, platelets, and/or fibrinogen concentrates, are used as a first line of defense to mitigate bleeding.1 Because of their critical roles in hemostasis, transfusion of platelets is particularly important for stopping uncontrolled bleeding. However, donor platelets have a short shelf life of approximately 5 to 7 days under standard storage conditions. The use of coldstored platelets is gaining popularity as a means to enhance platelet shelflife, but cold storage can cause platelet lesions and has not yet been widely adopted.2 Additionally, no matter the storage conditions used for platelets, because they are derived from human donors, platelet supply is dependent on donor availability and willingness, which often leads to shortages. This limitation has been particularly striking in the past year because the COVID19 pandemic has led to an unprecedented blood product storage. In fact, in 2022, for the first time, the American Red Cross declared a “blood crisis” and implored eligible donors to give blood.3 Furthermore, although risk of disease transmission is low because of current screening standards for donorderived products, this risk is still not zero.4 Finally, although platelets are a key therapeutic tool in the hospital setting, in emergency situations outside of a hospital, it is not practical to carry platelets or other blood products; therefore, many patients suffering traumatic bleeding have delays in critical treatment that could prevent morbidity and mortality.5 Overall, these limitations highlight that a great need exists to identify an alternative to natural platelets to treat bleeding. Ideally, this alternative should be readily available, have a long shelf life, have storage conditions that are amenable to use in emergency medicine, and perform in an equivalent manner to natural platelets. The creation of artificial platelets to meet these design goals has been an active area of research in recent years, and a new study by Sekhon et al. has demonstrated the creation of plateletmimicking procoagulant nanoparticles (PPNs) that have advanced platelet function compared with prior designs.6 Here, we discuss the implications for these new findings in the field of synthetic platelet design.}, journal={JOURNAL OF THROMBOSIS AND HAEMOSTASIS}, author={Nellenbach, Kimberly and Brown, Ashley C.}, year={2022}, month={Apr} }
 @article{moody_brown_massaro_patel_agarwalla_simpson_brown_zheng_pierce_brudno_2022, title={Restoring Carboxylates on Highly Modified Alginates Improves Gelation, Tissue Retention and Systemic Capture}, volume={138}, ISSN={["1878-7568"]}, url={https://doi.org/10.1016/j.actbio.2021.10.046}, DOI={10.1016/j.actbio.2021.10.046}, abstractNote={Alginate hydrogels are gaining traction for use in drug delivery, regenerative medicine, and as tissue engineered scaffolds due to their physiological gelation conditions, high tissue biocompatibility, and wide chemical versatility. Traditionally, alginate is decorated at the carboxyl group to carry drug payloads, peptides, or proteins. While low degrees of substitution do not cause noticeable mechanical changes, high degrees of substitution can cause significant losses to alginate properties including complete loss of calcium cross-linking. While most modifications used to decorate alginate deplete the carboxyl groups, we propose that alginate modifications that replenish the carboxyl groups could overcome the loss in gel integrity and mechanics. In this report, we demonstrate that restoring carboxyl groups during functionalization maintains calcium cross-links as well as hydrogel shear-thinning and self-healing properties. In addition, we demonstrate that alginate hydrogels modified to a high degree with azide modifications that restore the carboxyl groups have improved tissue retention at intramuscular injection sites and capture blood-circulating cyclooctynes better than alginate hydrogels modified with azide modifications that deplete the carboxyl groups. Taken together, alginate modifications that restore carboxyl groups could significantly improve alginate hydrogel mechanics for clinical applications. STATEMENT OF SIGNIFICANCE: Chemical modification of hydrogels provides a powerful tool to regulate cellular adhesion, immune response, and biocompatibility with local tissues. Alginate, due to its biocompatibility and easy chemical modification, is being explored for tissue engineering and drug delivery. Unfortunately, modifying alginate to a high degree of substitution consumes carboxyl group, which are necessary for ionic gelation, leading to poor hydrogel crosslinking. We introduce alginate modifications that restore the alginate's carboxyl groups. We demonstrate that modifications that reintroduce carboxyl groups restore gelation and improve gel mechanics and tissue retention. In addition to contributing to a basic science understanding of hydrogel properties, we anticipate our approach will be useful to create tissue engineered scaffolds and drug delivery platforms.}, journal={ACTA BIOMATERIALIA}, publisher={Elsevier BV}, author={Moody, C. T. and Brown, A. E. and Massaro, N. P. and Patel, A. S. and Agarwalla, P. A. and Simpson, A. M. and Brown, A. C. and Zheng, H. and Pierce, J. G. and Brudno, Y.}, year={2022}, month={Jan}, pages={208–217} }
 @article{nellenbach_kyu_guzzetta_brown_2021, title={Differential sialic acid content in adult and neonatal fibrinogen mediates differences in clot polymerization dynamics}, volume={5}, ISSN={["2473-9537"]}, DOI={10.1182/bloodadvances.2021004417.}, abstractNote={Neonates possess a molecular variant of fibrinogen, known as fetal fibrinogen, characterized by increased sialic acid, a greater negative charge, and decreased activity compared with adults. Despite these differences, adult fibrinogen is used for the treatment of bleeding in neonates, with mixed efficacy. To determine safe and efficacious bleeding protocols for neonates, more information on neonatal fibrin clot formation and the influence of sialic acid on these processes is needed. Here, we examine the influence of sialic acid on neonatal fibrin polymerization. We hypothesized that the increased sialic acid content of neonatal fibrinogen promotes fibrin B:b knob-hole interactions and consequently influences the structure and function of the neonatal fibrin matrix. We explored this hypothesis through analysis of structural properties and knob:hole polymerization dynamics of normal and desialylated neonatal fibrin networks and compared them with those formed with adult fibrinogen. We then characterized normal neonatal fibrin knob:hole interactions by forming neonatal and adult clots with either thrombin or snake-venom thrombin-like enzymes that preferentially cleave fibrinopeptide A or B. Sialic acid content of neonatal fibrinogen was determined to be a key determinant of resulting clot properties. Experiments analyzing knob:hole dynamics indicated that typical neonatal fibrin clots are formed with the release of more fibrinopeptide B and less fibrinopeptide A than adults. After the removal of sialic acid, fibrinopeptide release was roughly equivalent between adults and neonates, indicating the influence of sialic acid on fibrin neonatal fibrin polymerization mechanisms. These results could inform future studies developing neonatal-specific treatments of bleeding.}, number={23}, journal={BLOOD ADVANCES}, author={Nellenbach, Kimberly and Kyu, Alexander and Guzzetta, Nina and Brown, Ashley C.}, year={2021}, month={Dec}, pages={5202–5214} }
 @article{moiseiwitsch_nellenbach_guzzetta_brown_downey_2021, title={Ex Vivo and In Vivo Evaluation of Fibrinogen Concentrate to Mitigate Post-Surgical Bleeding in Neonates}, volume={138}, ISSN={["1528-0020"]}, DOI={10.1182/blood-2021-153823}, abstractNote={
 Introduction: Bleeding is a serious complication among neonates undergoing cardiopulmonary bypass (CPB) and it is linked to significant morbidity and mortality. Current standard of care treatment for bleeding after CPB focuses on the transfusion of adult blood products, including platelets and cryoprecipitate. However, prior work by Nellenbach et al. has demonstrated structural differences between neonatal and adult clotting components. Importantly, neonatal and adult fibrin do not fully integrate during clot formation which may contribute to ineffective clot formation and/or increased thrombotic risk following transfusion of adult cryoprecipitate to neonates. There has been increased interest in using human fibrinogen concentrate (HFC) in treating bleeding in the post-CPB neonate; however, HFC has not been validated in this population through evidence-based means. This study analyzed structural and degradation properties of post-CPB clots +/- the ex vivo addition of HFC and compared structural and degradation properties of post-CPB clots after the in vivo transfusion of HFC versus cryoprecipitate.
 Methods: Human neonatal plasma samples were collected from patients undergoing CPB at the Children's Hospital of Atlanta. For ex vivo studies, samples were taken at baseline, post-bypass, and post-transfusion of cryoprecipitate (n = 18 patients). Clots were formed for analysis from samples alone as well as post-bypass samples with the addition of 0.5 or 0.9 mg/mL HFC (RiaSTAP, CSL Behring) and structure was examined through confocal microscopy. Clot degradation was assessed through a microfluidic fibrinolysis assay. For in vivo studies, samples were taken at baseline, post-transfusion of cryoprecipitate or HFC, upon ICU arrival, and at 24 hours post-surgery (n = 36 patients). Clots were formed from samples and structure was examined through confocal microscopy. Clot degradation was assessed through a plate-based fibrinolysis assay.
 Results: In ex vivo studies, clot structural analysis demonstrated no significant differences in fiber density between samples collected at different time points (baseline = 0.541 ± 0.105, post-bypass = 0.431 ± 0.111, post-transfusion = 0.594 ± 0.170). The addition of 0.5 mg/mL or 0.9 mg/mL HFC to post-bypass samples led to a significant increase in fiber density (0.5 mg/mL HFC=0.654 ± 0.158, p=0.02; 0.9 mg/mL HFC= 0.797 ± 0.193, p<0.0001). Functional microfluidic analysis of clot degradation demonstrated significantly faster degradation times among post-bypass samples when compared to baseline samples (baseline degradation rate = 11.061 ± 6.087, post-bypass degradation rate = 25.906 ± 9.990 microns/hour, p=0.04). The addition of 0.5 mg/mL HFC resulted in a slower degradation rate from the original post-CPB degradation rate, but did not reach statistical significance (0.5 mg/mL HFC=14.091 ± 2.241, p=0.14). However, the addition of 0.9 mg/mL HFC resulted in a significantly slower degradation rate (0.9 mg/mL HFC=8.594 ± 6.087, p=0.01). Studies comparing in vivo transfusion of cryoprecipitate and HFC demonstrated no significant difference between treatment groups in clot density or degradation rate for any sample time point.
 Conclusion: We identify patterns in structural properties of clots formed after the transfusion of HFC that are consistent with successful hemostasis. However, caution is warranted regarding potentially thrombotic risks and should be carefully analyzed in future studies.
 Figure: Effect of Ex Vivo HFC Addition on Clot Structure and Degradation. (A) Representative confocal imaging of clots formed from different samples and HFC dosages (scale = 50 um). (B) Effect of HFC Addition on Clot Fiber Density. Addition of both 0.5 and 0.9 mg/mL HFC dosages to post-bypass sample result in statistically significant increases in fiber density compared to post-bypass samples. (C) Effect of HFC Addition on Clot Degradation Profiles. Addition of 0.9 mg/mL HFC to post-bypass sample leads to statistically significant slower fibrinolysis.
 Figure 1 Figure 1.
 
 
 
 Brown: Selsym Biotech, Inc.: Other: Co-Founder and CEO.
 
 
 
 RiaSTAP (human fibrinogen concentrate) is FDA approved for the treatment of congenital hypofibrinogenemia.
}, journal={BLOOD}, author={Moiseiwitsch, Nina and Nellenbach, Kimberly A. and Guzzetta, Nina A. and Brown, Ashley C. and Downey, Laura}, year={2021}, month={Nov} }
 @article{mihalko_sandry_mininni_nellenbach_deal_daniele_ghadimi_levy_brown_2021, title={Fibrin-modulating nanogels for treatment of disseminated intravascular coagulation}, volume={5}, ISSN={["2473-9537"]}, DOI={10.1182/bloodadvances.2020003046}, abstractNote={Disseminated intravascular coagulation (DIC) is a pathological coagulopathy associated with infection that increases mortality. In DIC, excessive thrombin generation causes symptoms from formation of microthrombi to multiorgan failure; bleeding risks can also be a concern because of clotting factor consumption. Different clinical events lead to DIC, including sepsis, trauma, and shock. Treatments for thrombotic episodes or bleeding presentation in DIC oppose each other, thus creating therapeutic dilemmas in management. The objective of this study was to develop fibrin-specific core-shell nanogels (FSNs) loaded with tissue-type plasminogen activator (tPA) to treat the microcirculatory complications of DIC, which would facilitate targeted clot dissolution to manage microthrombi and the potential consumptive coagulopathy that causes bleeding. FSNs enhance formation of actively polymerizing clots by crosslinking fibrin fibers, but they can also target preexisting microthrombi and, when loaded with tPA, facilitate targeted delivery to lyse the microthrombi. We hypothesized that this dual action would simultaneously address bleeding and microthrombi with DIC to improve outcomes. In vivo, tPA-FSNs decreased the presentation of multiorgan microthrombi, recovered platelet counts, and improved bleeding outcomes in a DIC rodent model. When incorporated with human DIC patient plasma, tPA-FSNs restored clot structure and clot growth under flow. Together, these data demonstrate that a fibrinolytic agent loaded into fibrin-targeting nanogels could improve DIC outcomes.}, number={3}, journal={BLOOD ADVANCES}, author={Mihalko, Emily P. and Sandry, Megan and Mininni, Nicholas and Nellenbach, Kimberly and Deal, Halston and Daniele, Michael and Ghadimi, Kamrouz and Levy, Jerrold H. and Brown, Ashley C.}, year={2021}, month={Feb}, pages={613–627} }
 @article{mihalko_nellenbach_krishnakumar_moiseiwitsch_sollinger_cooley_brown_2021, title={Fibrin-specific poly(N-isopropylacrylamide) nanogels for targeted delivery of tissue-type plasminogen activator to treat thrombotic complications are well tolerated in vivo}, ISSN={["2380-6761"]}, DOI={10.1002/btm2.10277}, abstractNote={Abstract Targeted drug delivery for maintaining blood fluidity can reduce the risks associated with systemic anticoagulants that can lead to off‐target bleeding. Recently, there has been much interest in targeted delivery of tissue‐type plasminogen activator (tPA) for treating thrombotic complications. The work presented here characterizes a fibrin‐specific nanogel (FSN) design for targeted delivery of tPA to treat thrombotic complications. Fibrin binding and clot degradation were characterized in vitro, and animal models of thrombosis were used to examine nanogel effects on coagulation parameters. In vitro assays showed tPA‐FSNs attach to fibrin in a dose‐dependent manner independent of tPA loading. In animal models of thrombosis, including an electrolytic injury to monitor clot properties in real time, and a lipopolysaccharide‐induced disseminated intravascular coagulation (DIC) animal model, tPA‐FSNs modulated fibrin/fibrinogen and platelet incorporation into clots and at optimized dosing could recover consumptive coagulopathy in DIC. Distribution of unloaded and tPA‐loaded FSNs showed potential clearance of tPA‐FSNs after 24 h, although unloaded FSNs may be retained at sites of fibrin deposits. Maximum tolerated dose studies showed tPA‐FSNs have minimal toxicity up to 20 times the optimized therapeutic dose. Overall, these studies demonstrate the therapeutic efficacy of targeted fibrinolysis for systemic microthrombi and begin to evaluate key translational parameters for tPA‐FSN therapeutics, including optimal tPA‐FSN dosage in a DIC rodent model and safety of intravenous tPA‐FSN therapeutics.}, journal={BIOENGINEERING & TRANSLATIONAL MEDICINE}, author={Mihalko, Emily P. and Nellenbach, Kimberly and Krishnakumar, Manasi and Moiseiwitsch, Nina and Sollinger, Jennifer and Cooley, Brian C. and Brown, Ashley C.}, year={2021}, month={Dec} }
 @article{pearce_nellenbach_smith_brown_haider_2021, title={Modeling and Parameter Subset Selection for Fibrin Polymerization Kinetics with Applications to Wound Healing}, volume={83}, ISSN={["1522-9602"]}, url={https://doi.org/10.1007/s11538-021-00876-6}, DOI={10.1007/s11538-021-00876-6}, abstractNote={During the hemostatic phase of wound healing, vascular injury leads to endothelial cell damage, initiation of a coagulation cascade involving platelets, and formation of a fibrin-rich clot. As this cascade culminates, activation of the protease thrombin occurs and soluble fibrinogen is converted into an insoluble polymerized fibrin network. Fibrin polymerization is critical for bleeding cessation and subsequent stages of wound healing. We develop a cooperative enzyme kinetics model for in vitro fibrin matrix polymerization capturing dynamic interactions among fibrinogen, thrombin, fibrin, and intermediate complexes. A tailored parameter subset selection technique is also developed to evaluate parameter identifiability for a representative data curve for fibrin accumulation in a short-duration in vitro polymerization experiment. Our approach is based on systematic analysis of eigenvalues and eigenvectors of the classical information matrix for simulations of accumulating fibrin matrix via optimization based on a least squares objective function. Results demonstrate robustness of our approach in that a significant reduction in objective function cost is achieved relative to a more ad hoc curve-fitting procedure. Capabilities of this approach to integrate non-overlapping subsets of the data to enhance the evaluation of parameter identifiability are also demonstrated. Unidentifiable reaction rate parameters are screened to determine whether individual reactions can be eliminated from the overall system while preserving the low objective cost. These findings demonstrate the high degree of information within a single fibrin accumulation curve, and a tailored model and parameter subset selection approach for improving optimization and reducing model complexity in the context of polymerization experiments.}, number={5}, journal={BULLETIN OF MATHEMATICAL BIOLOGY}, author={Pearce, Katherine J. and Nellenbach, Kimberly and Smith, Ralph C. and Brown, Ashley C. and Haider, Mansoor A.}, year={2021}, month={May} }
 @article{krissanaprasit_key_froehlich_pontula_mihalko_dupont_andersen_kjems_brown_labean_2021, title={Multivalent Aptamer-Functionalized Single-Strand RNA Origami as Effective, Target-Specific Anticoagulants with Corresponding Reversal Agents}, ISSN={["2192-2659"]}, DOI={10.1002/adhm.202001826}, abstractNote={Anticoagulants are commonly utilized during surgeries and to treat thrombotic diseases like stroke and deep vein thrombosis. However, conventional anticoagulants have serious side‐effects, narrow therapeutic windows, and lack safe reversal agents (antidotes). Here, an alternative RNA origami displaying RNA aptamers as target‐specific anticoagulant is described. Improved design and construction techniques for self‐folding, single‐molecule RNA origami as a platform for displaying pre‐selected RNA aptamers with precise orientational and spatial control are reported. Nuclease resistance is added using 2′‐fluoro‐modified pyrimidines during in vitro transcription. When four aptamers are displayed on the RNA origami platform, the measured thrombin inhibition and anticoagulation activity is higher than observed for free aptamers, ssRNA‐linked RNA aptamers, and RNA origami displaying fewer aptamers. Importantly, thrombin inhibition is immediately switched off by addition of specific reversal agents. Results for single‐stranded DNA (ssDNA) and single‐stranded peptide nucleic acid (PNA) antidotes show restoration of 63% and 95% coagulation activity, respectively. To demonstrate potential for practical, long‐term storage for clinical use, RNA origami is freeze‐dried, and stored at room temperature. Freshly produced and freeze‐dried RNA show identical levels of activity in coagulation assays. Compared to current commercial intravenous anticoagulants, RNA origami‐based molecules show promise as safer alternatives with rapid activity switching for future therapeutic applications.}, journal={ADVANCED HEALTHCARE MATERIALS}, author={Krissanaprasit, Abhichart and Key, Carson M. and Froehlich, Kristen and Pontula, Sahil and Mihalko, Emily and Dupont, Daniel M. and Andersen, Ebbe S. and Kjems, Jorgen and Brown, Ashley C. and LaBean, Thomas H.}, year={2021}, month={Apr} }
 @misc{moiseiwitsch_brown_2021, title={Neonatal coagulopathies: A review of established and emerging treatments}, volume={246}, ISSN={["1535-3699"]}, DOI={10.1177/15353702211006046}, abstractNote={Despite the relative frequency of both bleeding and clotting disorders among patients treated in the neonatal intensive care unit, few clear guidelines exist for treatment of neonatal coagulopathies. The study and treatment of neonatal coagulopathies are complicated by the distinct hemostatic balance and clotting components present during this developmental stage as well as the relative scarcity of studies specific to this age group. This mini-review examines the current understanding of neonatal hemostatic balance and treatment of neonatal coagulopathies, with particular emphasis on emerging treatment methods and areas in need of further investigative efforts.}, number={12}, journal={EXPERIMENTAL BIOLOGY AND MEDICINE}, author={Moiseiwitsch, Nina and Brown, Ashley C.}, year={2021}, month={Jun}, pages={1447–1457} }
 @article{todd_bharadwaj_nellenbach_nandi_mihalko_copeland_brown_stabenfeldt_2021, title={Platelet-like particles reduce coagulopathy-related and neuroinflammatory pathologies post-experimental traumatic brain injury}, ISSN={["1552-4981"]}, DOI={10.1002/jbm.b.34888}, abstractNote={Coagulopathy may occur following traumatic brain injury (TBI), thereby negatively affecting patient outcomes. Here, we investigate the use of platelet-like particles (PLPs), poly(N-isopropylacrylamide-co-acrylic-acid) microgels conjugated with a fibrin-specific antibody, to improve hemostasis post-TBI. The objective of this study was to diminish coagulopathy in a mouse TBI model (controlled cortical impact) via PLP treatment, and subsequently decrease blood-brain barrier (BBB) permeability and neuroinflammation. Following an acute intravenous injection of PLPs post-TBI, we analyzed BBB permeability, ex vivo coagulation parameters, and neuroinflammation at 24 hr and 7 days post-TBI. Both PLP-treatment and control particle-treatment had significantly decreased BBB permeability and improved clot structure 24 hr post-injury. Additionally, no significant change in tissue sparing was observed between 24 hr and 7 days for PLP-treated cohorts compared to that observed in untreated cohorts. Only PLP-treatment resulted in significant reduction of astrocyte expression at 7 days and percent difference from 24 hr to 7 days. Finally, PLP-treatment significantly reduced the percent difference from 24 hr to 7 days in microglia/macrophage density compared to the untreated control. These results suggest that PLP-treatment addressed acute hypocoagulation and decreased BBB permeability followed by decreased neuroinflammation and fold-change tissue loss by 7 days post-injury. These promising results indicate that PLPs could be a potential therapeutic modality for TBI.}, journal={JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS}, author={Todd, Jordan and Bharadwaj, Vimala N. and Nellenbach, Kimberly and Nandi, Seema and Mihalko, Emily and Copeland, Connor and Brown, Ashley C. and Stabenfeldt, Sarah E.}, year={2021}, month={Jun} }
 @article{roosa_muhamed_young_nellenbach_daniele_ligler_brown_2021, title={Synthesis of sonicated fibrin nanoparticles that modulate fibrin clot polymerization and enhance angiogenic responses}, volume={204}, ISSN={["1873-4367"]}, DOI={10.1016/j.colsurfb.2021.111805}, abstractNote={Chronic wounds can occur when the healing process is disrupted and the wound remains in a prolonged inflammatory stage that leads to severe tissue damage and poor healing outcomes. Clinically used treatments, such as high density, FDA-approved fibrin sealants, do not provide an optimal environment for native cell proliferation and subsequent tissue regeneration. Therefore, new treatments outside the confines of these conventional fibrin bulk gel therapies are required. We have previously developed flowable, low-density fibrin nanoparticles that, when coupled to keratinocyte growth factor, promote cell migration and epithelial wound closure in vivo. Here, we report a new high throughput method for generating the fibrin nanoparticles using probe sonication, which is less time intensive than the previously reported microfluidic method, and investigate the ability of the sonicated fibrin nanoparticles (SFBN) to promote clot formation and cell migration in vitro. The SFBNs can form a fibrin gel when combined with fibrinogen in the absence of exogenous thrombin, and the polymerization rate and fiber density in these fibrin clots is tunable based on SFBN concentration. Furthermore, fibrin gels made with SFBNs support cell migration in an in vitro angiogenic sprouting assay, which is relevant for wound healing. In this report, we show that SFBNs may be a promising wound healing therapy that can be easily produced and delivered in a flowable formulation.}, journal={COLLOIDS AND SURFACES B-BIOINTERFACES}, author={Roosa, Colleen A. and Muhamed, Ismaeel and Young, Ashlyn T. and Nellenbach, Kimberly and Daniele, Michael A. and Ligler, Frances S. and Brown, Ashley C.}, year={2021}, month={Aug} }
 @article{nandi_mihalko_nellenbach_castaneda_schneible_harp_deal_daniele_menegatti_barker_et al._2021, title={Synthetic Platelet Microgels Containing Fibrin Knob B Mimetic Motifs Enhance Clotting Responses}, volume={4}, ISSN={["2366-3987"]}, DOI={10.1002/adtp.202100010}, abstractNote={Native platelets are crucial players in wound healing. Key to their role is the ability of their surface receptor GPIIb/IIIa to bind fibrin at injury sites, thereby promoting clotting. When platelet activity is impaired as a result of traumatic injury or certain diseases, uncontrolled bleeding can result. To aid clotting and tissue repair in cases of poor platelet activity, synthetic platelet‐like particles capable of promoting clotting and improving wound healing responses have been previously developed in the lab. These are constructed by functionalizing highly deformable hydrogel microparticles (microgels) with fibrin‐binding ligands including a fibrin‐specific whole antibody or a single‐domain variable fragment. To improve the translational potential of these clotting materials, the use of fibrin‐binding peptides as cost‐effective, robust, high‐specificity alternatives to antibodies are explored. Herein, the development and characterization of soft microgels decorated with the peptide AHRPYAAK that mimics fibrin knob “B” and targets fibrin hole “b” are presented. These “fibrin‐affine microgels with clotting yield” (FAMCY) are found to significantly increase clot density in vitro and decrease bleeding in a rodent trauma model in vivo. These results indicate that FAMCYs are capable of recapitulating the platelet‐mimetic properties of previous designs while utilizing a less costly, more translational design.}, number={5}, journal={ADVANCED THERAPEUTICS}, author={Nandi, Seema and Mihalko, Emily and Nellenbach, Kimberly and Castaneda, Mario and Schneible, John and Harp, Mary and Deal, Halston and Daniele, Michael and Menegatti, Stefano and Barker, Thomas H. and et al.}, year={2021}, month={May} }
 @misc{chee_brown_2020, title={Biomimetic antimicrobial material strategies for combating antibiotic resistant bacteria}, volume={8}, ISSN={["2047-4849"]}, DOI={10.1039/c9bm01393h}, abstractNote={Antibiotic drugs have revolutionized the field of medicine for almost 90 years. However, continued use has led to the rise of antibiotic resistant bacteria, motivating the need for alternative treatments. Several strategies to combat this phenomenon have been investigated, with biomimetic strategies gaining significant appeal due to inherent compatibility with physiologically relevant environments. In this review, we will discuss current antimicrobial strategies and then present an overview on biomimetic antimicrobial material-based strategies for combating antibiotic resistant bacteria.}, number={4}, journal={BIOMATERIALS SCIENCE}, author={Chee, Eunice and Brown, Ashley C.}, year={2020}, month={Feb}, pages={1089–1100} }
 @misc{mihalko_brown_2020, title={Clot Structure and Implications for Bleeding and Thrombosis}, volume={46}, ISSN={["1098-9064"]}, DOI={10.1055/s-0039-1696944}, abstractNote={Abstract The formation of a fibrin clot matrix plays a critical role in promoting hemostasis and wound healing. Fibrin dynamics can become disadvantageous in the formation of aberrant thrombus development. Structural characteristics of clots, such as fiber diameter, clot density, stiffness, or permeability, can determine overall clot integrity and functional characteristics that have implications on coagulation and fibrinolysis. This review examines known factors that contribute to changes in clot structure and the presence of structural clot changes in various disease states. These insights provide valuable information in forming therapeutic strategies for disease states where alterations in clot structure are observed. Additionally, the implications of structural changes in clot networks on bleeding and thrombus development in terms of disease states and clinical outcomes are also examined in this review.}, number={1}, journal={SEMINARS IN THROMBOSIS AND HEMOSTASIS}, author={Mihalko, Emily and Brown, Ashley C.}, year={2020}, month={Feb}, pages={96–104} }
 @article{sproul_nandi_chee_sivadanam_igo_schreck_brown_2020, title={Development of Biomimetic Antimicrobial Platelet-Like Particles Comprised of Microgel Nanogold Composites}, volume={6}, ISSN={["2364-4141"]}, DOI={10.1007/s40883-019-00121-6}, abstractNote={A blood clot is formed in response to bleeding by platelet aggregation and adherence to fibrin fibers. Platelets contract over time, stabilizing the clot, which contributes to wound healing. We have developed platelet-like particles (PLPs) that augment clotting and induce clot retraction by mimicking the fibrin-binding capabilities and morphology of native platelets. Wound repair following hemostasis can be complicated by infection; therefore, we aim to augment wound healing by combining PLPs with antimicrobial gold to develop nanogold composites (NGCs). PLPs were synthesized with N-isopropylacrylamide (NIPAm)/co-acrylic acid in a precipitation polymerization reaction and conjugated to a fibrin-specific antibody. Two methods were employed to create NGCs: (1) noncovalent swelling with aqueous gold nanospheres, and (2) covalent seeding and growth. Since the ability of PLPs to mimic platelet morphology and clot retraction requires a high degree of particle deformability, we investigated how PLPs created from NGCs affected these properties. Cryogenic scanning electron microscopy (cryoSEM) and atomic force microscopy (AFM) demonstrated that particle deformability, platelet-mimetic morphology, and clot retraction were maintained in NGC-based PLPs. The effect of NGCs on bacterial adhesion and growth was assessed with antimicrobial assays. These results demonstrate NGCs fabricated through noncovalent and covalent methods retain deformability necessary for clot collapse and exhibit some antimicrobial potential. Therefore, NGCs are promising materials for preventing hemorrhage and infection following trauma. Following injury, a blood clot is formed by platelets aggregating and binding to fibrin fibers. Platelets contract over time, stabilizing the clot, which contributes to wound healing. We have developed PLPs that enhance clotting and stimulate clot retraction by mimicking the fibrin-binding capabilities and morphology of native platelets. Wound repair following hemostasis can be complicated by infection; therefore, we aim to amplify wound healing by combining PLPs with antimicrobial gold to develop NGCs. These NGC PLPs mimic platelet morphology, generate clot retraction, demonstrate some antimicrobial potential, and are promising materials for preventing blood loss and infection following trauma. Future work will include exploring the application of these particles to treat hemorrhage and infection following traumatic injury.}, number={3}, journal={REGENERATIVE ENGINEERING AND TRANSLATIONAL MEDICINE}, author={Sproul, Erin P. and Nandi, Seema and Chee, Eunice and Sivadanam, Supriya and Igo, Benjamin J. and Schreck, Luisa and Brown, Ashley C.}, year={2020}, month={Sep}, pages={299–309} }
 @article{huebner_warren_chester_spang_brown_fisher_shirwaiker_2020, title={Mechanical properties of tissue formed in vivo are affected by 3D-bioplotted scaffold microarchitecture and correlate with ECM collagen fiber alignment}, volume={61}, ISSN={["1607-8438"]}, DOI={10.1080/03008207.2019.1624733}, abstractNote={ABSTRACT Purpose: Musculoskeletal soft tissues possess highly aligned extracellular collagenous networks that provide structure and strength. Such an organization dictates tissue-specific mechanical properties but can be difficult to replicate by engineered biological substitutes. Nanofibrous electrospun scaffolds have demonstrated the ability to control cell-secreted collagen alignment, but concerns exist regarding their scalability for larger and anatomically relevant applications. Additive manufacturing processes, such as melt extrusion-based 3D-Bioplotting, allow fabrication of structurally relevant scaffolds featuring highly controllable porous microarchitectures. Materials and Methods: In this study, we investigate the effects of 3D-bioplotted scaffold design on the compressive elastic modulus of neotissue formed in vivo in a subcutaneous rat model and its correlation with the alignment of ECM collagen fibers. Polycaprolactone scaffolds featuring either 100 or 400 µm interstrand spacing were implanted for 4 or 12 weeks, harvested, cryosectioned, and characterized using atomic-force-microscopy-based force mapping. Results: The compressive elastic modulus of the neotissue formed within the 100 µm design was significantly higher at 4 weeks (p < 0.05), but no differences were observed at 12 weeks. In general, the tissue stiffness was within the same order of magnitude and range of values measured in native musculoskeletal soft tissues including the porcine meniscus and anterior cruciate ligament. Finally, a significant positive correlation was noted between tissue stiffness and the degree of ECM collagen fiber alignment (p < 0.05) resulting from contact guidance provided by scaffold strands. Conclusion: These findings demonstrate the significant effects of 3D-bioplotted scaffold microarchitectures in the organization and sub-tissue-level mechanical properties of ECM in vivo.}, number={2}, journal={CONNECTIVE TISSUE RESEARCH}, author={Huebner, Pedro and Warren, Paul B. and Chester, Daniel and Spang, Jeffrey T. and Brown, Ashley C. and Fisher, Matthew B. and Shirwaiker, Rohan A.}, year={2020}, month={Mar}, pages={190–204} }
 @misc{deal_brown_daniele_2020, title={Microphysiological systems for the modeling of wound healing and evaluation of pro-healing therapies}, volume={8}, ISSN={["2050-7518"]}, DOI={10.1039/d0tb00544d}, abstractNote={Wound healing is a multivariate process involving the coordinated response of numerous proteins and cell types. Accordingly, biomedical research has seen an increased adoption of the use of in vitro wound healing assays with complexity beyond that offered by traditional well-plate constructs. These microphysiological systems (MPS) seek to recapitulate one or more physiological features of the in vivo microenvironment, while retaining the analytical capacity of more reductionist assays. Design efforts to achieve relevant wound healing physiology include the use of dynamic perfusion over static culture, the incorporation of multiple cell types, the arrangement of cells in three dimensions, the addition of biomechanically and biochemically relevant hydrogels, and combinations thereof. This review provides a brief overview of the wound healing process and in vivo assays, and we critically review the current state of MPS and supporting technologies for modelling and studying wound healing. We distinguish between MPS that seek to inform a particular phase of wound healing, and constructs that have the potential to inform multiple phases of wound healing. This distinction is a product of whether analysis of a particular process is prioritized, or a particular physiology is prioritized, during design. Material selection is emphasized throughout, and relevant fabrication techniques discussed.}, number={32}, journal={JOURNAL OF MATERIALS CHEMISTRY B}, author={Deal, Halston E. and Brown, Ashley C. and Daniele, Michael A.}, year={2020}, month={Aug}, pages={7062–7075} }
 @article{chee_nandi_nellenbach_mihalko_snider_morrill_bond_sproul_sollinger_cruse_et al._2020, title={Nanosilver composite pNIPAm microgels for the development of antimicrobial platelet-like particles}, volume={108}, ISSN={["1552-4981"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85080073268&partnerID=MN8TOARS}, DOI={10.1002/jbm.b.34592}, abstractNote={Platelets crucially facilitate wound healing but can become depleted in traumatic injury or chronic wounds. Previously, our group developed injectable platelet-like particles (PLPs) comprised of highly deformable, ultralow crosslinked pNIPAm microgels (ULCs) coupled to fibrin binding antibodies to treat post-trauma bleeding. PLP fibrin-binding facilitates homing to sites of injury, promotes clot formation, and, due to high particle deformability, induces clot retraction. Clot retraction augments healing by increasing clot stability, enhancing clot stiffness, and promoting cell migration into the wound bed. Because post-traumatic healing is often complicated by infection, the objective of these studies was to develop antimicrobial nanosilver microgel composite PLPs to augment hemostasis, fight infection, and promote healing post-trauma. A key goal was to maintain particle deformability following silver incorporation to preserve PLP-mediated clot retraction. Clot retraction, antimicrobial activity, hemostasis after trauma, and healing after injury were evaluated via confocal microscopy, colony-forming unit assays, a murine liver trauma model, and a murine full-thickness injury model in the absence or presence of infection, respectively. We found that nanosilver incorporation does not affect base PLP performance while bestowing significant antimicrobial activity and enhancing infected wound healing outcomes. Therefore, Ag-PLPs have great promise for treating hemorrhage and improving healing following trauma.}, number={6}, journal={JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS}, author={Chee, Eunice and Nandi, Seema and Nellenbach, Kimberly and Mihalko, Emily and Snider, Douglas B. and Morrill, Landon and Bond, Andrew and Sproul, Erin and Sollinger, Jennifer and Cruse, Glenn and et al.}, year={2020}, month={Aug}, pages={2599–2609} }
 @article{nellenbach_nandi_peeler_kyu_brown_2020, title={Neonatal Fibrin Scaffolds Promote Enhanced Cell Adhesion, Migration, and Wound Healing In Vivo Compared to Adult Fibrin Scaffolds}, ISBN={1865-5033}, DOI={10.1007/s12195-020-00620-5}, abstractNote={Fibrin scaffolds are often utilized to treat chronic wounds. The monomer fibrinogen used to create such scaffolds is typically derived from adult human or porcine plasma. However, our previous studies have identified extensive differences in fibrin network properties between adults and neonates, including higher fiber alignment in neonatal networks. Wound healing outcomes have been linked to fibrin matrix structure, including fiber alignment, which can affect the binding and migration of cells. We hypothesized that fibrin scaffolds derived from neonatal fibrin would enhance wound healing outcomes compared to adult fibrin scaffolds.Fibrin scaffolds were formed from purified adult or neonatal fibrinogen and thrombin then structural analysis was conducted via confocal microscopy. Human neonatal dermal fibroblast attachment, migration, and morphology on fibrin scaffolds were assessed. A murine full thickness injury model was used to compare healing in vivo in the presence of neonatal fibrin, adult fibrin, or saline.Distinct fibrin architectures were observed between adult and neonatal scaffolds. Significantly higher fibroblast attachment and migration was observed on neonatal scaffolds compared to adults. Cell morphology on neonatal scaffolds exhibited higher spreading compared to adult scaffolds. In vivo significantly smaller wound areas and greater epidermal thickness were observed when wounds were treated with neonatal fibrin compared to adult fibrin or a saline control.Distinctions in neonatal and adult fibrin scaffold properties influence cellular behavior and wound healing. These studies indicate that fibrin scaffolds sourced from neonatal plasma could improve healing outcomes compared to scaffolds sourced from adult plasma.}, journal={CELLULAR AND MOLECULAR BIOENGINEERING}, author={Nellenbach, Kimberly and Nandi, Seema and Peeler, Christopher and Kyu, Alexander and Brown, Ashley C.}, year={2020} }
 @article{nandi_sommerville_nellenbach_mihalko_erb_freytes_hoffman_monroe_brown_2020, title={Platelet-like particles improve fibrin network properties in a hemophilic model of provisional matrix structural defects}, volume={577}, ISSN={["1095-7103"]}, DOI={10.1016/j.jcis.2020.05.088}, abstractNote={Following injury, a fibrin-rich provisional matrix is formed to stem blood loss and provide a scaffold for infiltrating cells, which rebuild the damaged tissue. Defects in fibrin network formation contribute to impaired healing outcomes, as evidenced in hemophilia. Platelet-fibrin interactions greatly influence fibrin network structure via clot contraction, which increases fibrin density over time. Previously developed hemostatic platelet-like particles (PLPs) are capable of mimicking platelet functions including binding to fibrin fibers, augmenting clotting, and inducing clot retraction. In this study, we aimed to apply PLPs within a plasma-based in vitro hemophilia B model of deficient fibrin network structure to determine the ability of PLPs to improve fibrin structure and wound healing responses within hemophilia-like abnormal fibrin network formation. PLP impact on structurally deficient clot networks was assessed via confocal microscopy, a micropost deflection model, atomic force microscopy and an in vitro wound healing model of early cell migration within a provisional fibrin matrix. PLPs improved clot network density, force generation, and stiffness, and promoted fibroblast migration within an in vitro model of early wound healing under hemophilic conditions, indicating that PLPs could provide a biomimetic platform for improving wound healing events in disease conditions that cause deficient fibrin network formation.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Nandi, Seema and Sommerville, Laura and Nellenbach, Kimberly and Mihalko, Emily and Erb, Mary and Freytes, Donald O. and Hoffman, Maureane and Monroe, Dougald and Brown, Ashley C.}, year={2020}, month={Oct}, pages={406–418} }
 @article{chester_theetharappan_ngobili_daniele_brown_2020, title={Ultrasonic Microplotting of Microgel Bioinks}, volume={12}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.0c15056}, abstractNote={Material scaffolds that mimic the structure, function, and bioactivity of native biological tissues are in constant development. Recently, material scaffolds composed of microgel particles have shown promise for applications ranging from bone regeneration to spheroid cell growth. Previous studies with poly N-isopropylacrylamide microgel scaffolds utilized a layer-by-layer (LBL) technique where individual, uniform microgel layers are built on top of each other resulting in a multilayer scaffold. However, this technique is limited in its applications due to the inability to control microscale deposition or patterning of multiple particle types within a microgel layer. In this study, an ultrasonic microplotting technique is used to address the limitations of LBL fabrication to create patterned microgel films. Printing parameters, such as bioink formulation, surface contact angle, and print head diameter, are optimized to identify the ideal parameters needed to successfully print microgel films. It was found that bioinks composed of 2 mg/mL of microgels and 20% polyethylene glycol by volume (v/v), on bovine serum albumin-coated glass, with a print head diameter of 50 μm resulted in the highest quality prints. Patterned films were created with a maximum resolution of 50 μm with the potential for finer resolutions to be achieved with alternative bioink compositions and printing parameters. Overall, ultrasonic microplotting can be used to create more complex microgel films than is possible with LBL techniques and offers the possibility of greater printing resolution in 3D with further technology development.}, number={42}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Chester, D. and Theetharappan, P. and Ngobili, T. and Daniele, M. and Brown, A. C.}, year={2020}, month={Oct}, pages={47309–47319} }
 @article{nandi_mohanty_nellenbach_erb_muller_brown_2020, title={Ultrasound Enhanced Synthetic Platelet Therapy for Augmented Wound Repair}, volume={6}, ISSN={["2373-9878"]}, DOI={10.1021/acsbiomaterials.9b01976}, abstractNote={Native platelets perform a number of functions within the wound healing process, including interacting with fibrin fibers at the wound site to bring about retraction after clot formation. Clot retraction improves clot stability and enhances the function of the fibrin network as a provisional matrix to support cellular infiltration of the wound site, thus facilitating tissue repair and remodeling after hemostasis. In cases of traumatic injury or disease, platelets can become depleted and this process disrupted. To that end, our lab has developed synthetic platelet-like particles (PLPs) that recapitulate the clot retraction abilities of native platelets through a Brownian-wrench driven mechanism that drives fibrin network densification and clot retraction over time, however, this Brownian-motion driven process occurs on a longer time scale than native active actin/myosin-driven platelet-mediated clot retraction. We hypothesized that a combinatorial therapy comprised of ultrasound stimulation of PLP motion within fibrin clots would facilitate a faster induction of clot retraction on a more platelet-mimetic time scale and at a lower dosage than required for PLPs acting alone. We found that application of ultrasound in combination with a subtherapeutic dosage of PLPs resulted in increased clot density and stiffness, improved fibroblast migration in vitro and increased epidermal thickness and angiogenesis in vivo, indicating that this combination therapy has potential to facilitate multiphase pro-healing outcomes. Additionally, while these particular studies focus on the role of ultrasound in enhancing specific interactions between fibrin-binding synthetic PLPs embedded within fibrin networks, these studies have wide applicability in understanding the role of ultrasound stimulation in enhancing multi-scale colloidal interactions within fibrillar matrices.}, number={5}, journal={ACS BIOMATERIALS SCIENCE & ENGINEERING}, author={Nandi, Seema and Mohanty, Kaustav and Nellenbach, Kimberly and Erb, Mary and Muller, Marie and Brown, Ashley C.}, year={2020}, month={May}, pages={3026–3036} }
 @misc{brown_lavik_stabenfeldt_2019, title={Biomimetic Strategies To Treat Traumatic Brain Injury by Leveraging Fibrinogen}, volume={30}, ISSN={["1520-4812"]}, DOI={10.1021/acs.bioconjchem.9b00360}, abstractNote={There were over 27 million new cases of traumatic brain injuries (TBIs) in 2016 across the globe. TBIs are often part of complicated trauma scenarios and may not be diagnosed initially as primary clinical focus is on stabilizing the patient. Interventions used to stabilize trauma patients may inadvertently impact the outcomes of TBIs. Recently, there has been a strong interest in the trauma community towards administrating fibrinogen-containing solutions intravenously to help stabilize trauma patients. While this interventional shift may benefit general trauma scenarios, fibrinogen is associated with potentially deleterious effects for TBIs. Here, we deconstruct what components of fibrinogen may be beneficial as well as, potentially harmful, following TBI and extrapolate this to biomimetic approaches to treat bleeding and trauma that may, also, lead to better outcomes following TBI.}, number={7}, journal={BIOCONJUGATE CHEMISTRY}, author={Brown, Ashley C. and Lavik, Erin and Stabenfeldt, Sarah E.}, year={2019}, month={Jul}, pages={1951–1956} }
 @article{muhamed_sproul_ligler_brown_2019, title={Fibrin Nanoparticles Coupled with Keratinocyte Growth Factor Enhance the Dermal Wound-Healing Rate}, volume={11}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.8b21056}, abstractNote={Expediting the wound-healing process is critical for patients chronically ill from nonhealing wounds and diseases such as hemophilia or diabetes or who have suffered trauma including easily infected open wounds. FDA-approved external tissue sealants include the topical application of fibrin gels, which can be 500 times denser than natural fibrin clots. With lower clot porosity and higher polymerization rates than physiologically formed fibrin clots, the commercial gels quickly stop blood loss but impede the later clot degradation kinetics and thus retard tissue-healing rates. The fibrin nanoparticles (FBNs) described here are constructed from physiologically relevant fibrin concentrations that support new tissue and dermal wound scaffold formation when coupled with growth factors. The FBNs, synthesized in a microfluidic droplet generator, support cell adhesion and traction generation, and when coupled to keratinocyte growth factor (KGF), support cell migration and in vivo wound healing. The FBN-KGF particles enhance cell migration in vitro greater than FBN alone or free KGF and also improve healing outcomes in a murine full thickness injury model compared to saline, bulk fibrin sealant, free KGF, or bulk fibrin mixed with KGF treatments. Furthermore, FBN can be potentially administered with other tissue-healing factors and inflammatory mediators to improve wound-healing outcomes.}, number={4}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Muhamed, Ismaeel and Sproul, Erin P. and Ligler, Frances S. and Brown, Ashley C.}, year={2019}, month={Jan}, pages={3771–3780} }
 @article{brown_levy_2019, title={Maintaining Hemostatic Balance in Treating Disseminated Intravascular Coagulation}, volume={131}, ISSN={["1528-1175"]}, DOI={10.1097/ALN.0000000000002862}, abstractNote={Disseminated intravascular coagulation (DIC) is a complex coagulopathic state that can present as a thromboinflammatory response to diverse causes that include septic shock, traumatic injury, pregnancy, and cancer. The International Society on Thrombosis and Hemostasis (Carrboro, North Carolina) defines DIC as “an acquired syndrome characterized by the intravascular activation of coagulation with loss of localization arising from different causes that can originate from and cause damage to the microvasculature, which if sufficiently severe, can produce organ dysfunction.” In DIC, endothelial injury and microcirculatory abnormalities produced by hemostatic abnormalities cause multiorgan failure. Of note is that DIC is not a primary disease state, but rather a pathophysiologic response to an underlying disease process, and is based on laboratory diagnosis. The clinical (phenotypic) manifestations can range as a spectrum of either bleeding or thrombotic manifestation due to causes that include the underlying disease process (e.g., cancer-induced DIC), or the time course of diagnosis and therapy. The basis of therapy for DIC is to treat the underlying disease, but also provide temporary support of the coagulation disorder and coagulopathy that depends on whether patients present with bleeding or thrombotic phenotypes. The complexity of managing DIC is to balance both the bleeding and thrombotic complications that occur. In the current edition of the Anesthesiology, Grottke et al. evaluated, in a porcine trauma model, whether prothrombin complex concentrate–induced DIC could be prevented by coadministering antithrombin, a physiologic anticoagulant. They evaluated multiple procoagulant and anticoagulant combinations including tranexamic acid in their multiorgan trauma model that included femur fractures, thoracic contusion, and blunt liver injury. Although prothrombin concentrates reduced bleeding, there were thromboembolic complications (pulmonary emboli) that can occur in clinical DIC. However, when antithrombin was administered in combination with prothrombin concentrate and/or fibrinogen concentrate, DIC did not occur, and there were no early deaths in the fibrinogen concentrate plus prothrombin concentrates plus antithrombin group. Collectively, these studies demonstrate that following experimental animal trauma, administration of prothrombin complex concentrates, either alone or in combination with fibrinogen concentrate, can potentially induce hypercoagulability, but coadministration of antithrombin mitigated this effect. What can we learn from this model of coagulopathy when there are multiple causes of bleeding and thrombosis that have been extensively characterized and have many of the similar characteristics of DIC? European trauma guidelines are increasingly considering prothrombin concentrates as part of a multimodal approach to managing bleeding compared to fresh frozen plasma for rapid factor administration due to their availability without the need for cross-matching. In a bleeding coagulopathic patient, the critical management strategy is to administer products that create a thrombotic milieu; the question is how to balance the risk of thrombotic complications, consumptive coagulopathy, or potentially DIC. 2019 “The complexity of managing DIC [disseminated intravascular coagulation] is to balance both the bleeding and thrombotic complications that occur.”}, number={3}, journal={ANESTHESIOLOGY}, author={Brown, Ashley C. and Levy, Jerrold H.}, year={2019}, month={Sep}, pages={459–461} }
 @article{nandi_sproul_nellenbach_erb_gaffney_freytes_brown_2019, title={Platelet-like particles dynamically stiffen fibrin matrices and improve wound healing outcomes}, volume={7}, ISSN={["2047-4849"]}, DOI={10.1039/c8bm01201f}, abstractNote={Native platelets perform several critical functions within the context of wound healing, including participating in initial hemostasis and interacting with fibrin at the wound site to induce clot retraction. Platelet depletion or dysfunction due to trauma or disease can inhibit robust wound healing responses. There has been a focus recently on developing synthetic, non-immunogenic platelet mimetic technologies for the purpose of augmenting hemostatic responses in cases of deficient native platelet functionality. Here we describe the application of synthetic platelet-like particles (PLPs), capable of recapitulating the deformable platelet body and fibrin specificity found in native platelets, to enhance healing outcomes. We first demonstrate PLPs mimic activated platelet morphology and induce fibrin clot retraction. During clot retraction, native platelets generate forces within a fibrin network to stiffen the fibrin matrix; therefore, we hypothesized that our PLPs will likewise be able to stiffen provisional fibrin matrices. Due to previous studies indicating that increased matrix stiffness is linked to increased cellular migration, we further hypothesize that PLP-mediated fibrin stiffening will enhance cell migration and improve healing outcomes within in vitro and in vivo models of wound healing. PLPs were found to enhance fibroblast migration in in vitro models of early wound healing and enhance healing outcomes in an in vivo murine model of wound healing. These studies demonstrate the utility of PLPs for enhancing wound repair and also provide insight into the role of native platelet-mediated clot retraction in wound healing.}, number={2}, journal={BIOMATERIALS SCIENCE}, author={Nandi, Seema and Sproul, Erin P. and Nellenbach, Kimberly and Erb, Mary and Gaffney, Lewis and Freytes, Donald O. and Brown, Ashley C.}, year={2019}, month={Feb}, pages={669–682} }
 @article{chester_marrow_daniele_brown_2019, title={Wound Healing and the Host Response in Regenerative Engineering}, DOI={10.1016/B978-0-12-801238-3.99896-9}, abstractNote={Wound healing is a complex and highly controlled process responsible for maintaining and reestablishing the homeostatic structure, function, and properties of tissues. This process becomes substantially more complicated upon the introduction of a foreign material. The purpose of this book chapter is to highlight the cellular processes and bioactive agents that encompass the wound healing process and to discuss how these processes change in the presence of a biomaterial. Common biomaterials that are used to direct the wound healing process are also discussed.}, journal={ENCYCLOPEDIA OF BIOMEDICAL ENGINEERING, VOL 1}, author={Chester, Daniel and Marrow, Ethan A. and Daniele, Michael A. and Brown, Ashley C.}, year={2019}, pages={707–718} }
 @article{sproul_nandi_roosa_schreck_brown_2018, title={Biomimetic Microgels with Controllable Deformability Improve Healing Outcomes}, volume={2}, ISSN={["2366-7478"]}, DOI={10.1002/adbi.201800042}, abstractNote={Platelets mediate hemostasis by aggregating and binding to fibrin to promote clotting. Over time, platelets contract the fibrin network to induce clot retraction, which contributes to wound healing outcomes by increasing clot stability and improving blood flow to ischemic tissue. In this study, the development of hollow platelet‐like particles (PLPs) that mimic the native platelet function of clot retraction in a controlled manner is described and it is demonstrated that clot retraction‐inducing PLPs promote healing in vivo. PLPs are created by coupling fibrin‐binding antibodies to CoreShell (CS) or hollow N‐isopropylacrylamide (NIPAm) microgels with varying degrees of shell crosslinking. It is demonstrated that hollow microgels with loosely crosslinked shells display a high degree of deformability and mimic activated platelet morphology, while intact CS microgels and hollow microgels with increased crosslinking in the shell do not. When coupled to a fibrin‐binding antibody to create PLPs, hollow particles with low degrees of shell crosslinking cause fibrin clot collapse in vitro, recapitulating the clot retraction function of platelets, while other particle types do not. Furthermore, hollow PLPs with low degrees of shell crosslinking improve some wound healing outcomes in vivo.}, number={10}, journal={ADVANCED BIOSYSTEMS}, author={Sproul, Erin P. and Nandi, Seema and Roosa, Colleen and Schreck, Luisa and Brown, Ashley C.}, year={2018}, month={Oct} }
 @article{welsch_brown_barker_lyon_2018, title={Enhancing clot properties through fibrin-specific self-cross-linked PEG side-chain microgels}, volume={166}, ISSN={["1873-4367"]}, DOI={10.1016/j.colsurfb.2018.03.003}, abstractNote={Excessive bleeding and resulting complications are a major cause of death in both trauma and surgical settings. Recently, there have been a number of investigations into the design of synthetic hemostatic agents with platelet-mimicking activity to effectively treat patients suffering from severe hemorrhage. We developed platelet-like particles from microgels composed of polymers carrying polyethylene glycol (PEG) side-chains and fibrin-targeting single domain variable fragment antibodies (PEG-PLPs). Comparable to natural platelets, PEG-PLPs were found to enhance the fibrin network formation in vitro through strong adhesion to the emerging fibrin clot and physical, non-covalent cross-linking of nascent fibrin fibers. Furthermore, the mechanical reinforcement of the fibrin mesh through the incorporation of particles into the network leads to a ∼three-fold decrease of the overall clot permeability as compared to control clots. However, transport of biomolecules through the fibrin clots, such as peptides and larger proteins is not hindered by the presence of PEG-PLPs and the altered microstructure. Compared to control clots with an elastic modulus of 460+/-260 Pa, PEG-PLP-reinforced fibrin clots exhibit higher degrees of stiffness as demonstrated by the significantly increased average Younǵs modulus of 1770 +/±720 Pa, as measured by AFM force spectroscopy. Furthermore, in vitro degradation studies with plasmin demonstrate that fibrin clots formed in presence of PEG-PLPs withstand hydrolysis for 24 h, indicating enhanced stabilization against exogenous fibrinolysis. The entire set of data suggests that the designed platelet-like particles have high potential for use as hemostatic agents in emergency medicine and surgical settings.}, journal={COLLOIDS AND SURFACES B-BIOINTERFACES}, author={Welsch, Nicole and Brown, Ashley C. and Barker, Thomas H. and Lyon, L. Andrew}, year={2018}, month={Jun}, pages={89–97} }
 @article{sproul_nandi_brown_2018, title={Fibrin biomaterials for tissue regeneration and repair}, ISBN={["978-0-08-100803-4"]}, ISSN={["2049-9485"]}, DOI={10.1016/b978-0-08-100803-4.00006-1}, abstractNote={Fibrin is an integral part of the clotting cascade and is formed by polymerization of the soluble plasma protein fibrinogen. Following the stimulation of the coagulation cascade, thrombin activates fibrinogen, which binds to adjacent fibrin(ogen) molecules resulting in the formation of an insoluble fibrin matrix. This fibrin network is the primary protein component in clots and subsequently provides a scaffold for infiltrating cells during tissue repair. Due to its role in hemostasis and tissue repair, fibrin has been used extensively as a tissue sealant. This chapter first provides an overview of the structure and function of fibrin(ogen) and details the role of fibrin-cell interactions in wound repair. The design and use of fibrin-based materials for promoting tissue repair is also discussed.}, journal={PEPTIDES AND PROTEINS AS BIOMATERIALS FOR TISSUE REGENERATION AND REPAIR}, author={Sproul, E. and Nandi, S. and Brown, A.}, year={2018}, pages={151–173} }
 @article{hardy_wang_iyer_mannino_sakurai_barker_chi_youn_wang_brown_et al._2018, title={Interdigitated microelectronic bandage augments hemostasis and clot formation at low applied voltage in vitro and in vivo}, volume={18}, ISSN={["1473-0189"]}, DOI={10.1039/c8lc00573g}, abstractNote={Hemorrhage or uncontrolled bleeding can arise either due to a medical condition or from a traumatic injury and are typically controlled with the application of a hemostatic agent. Hemostatic agents are currently derived from animal or human products, which carry risks of blood borne infections and immune dysregulation. Therefore, the need exists for novel biomedical therapies not derived from animal or human products to achieve hemostasis. Accordingly, we created an interdigitated microelectronic bandage that applies low voltage electrical stimulation to an injury site, resulting in faster clot formation without excessive heating, accelerated fibrin formation, and hemostasis overall. Our interdigitated microelectronic bandage found fibrin formed 1.5× faster in vitro. In vivo, total cessation of bleeding was 2.5× faster, resulting in 2× less blood loss. Electricity has been used in medical applications such as defibrillation, cauterization, and electrosurgery, but scant research has focused on hemostasis. Here we report a novel surface treatment using an interdigitated microelectronic device that creates rapid hemostasis in both in vitro and in vivo bleeding models with low applied voltages, representing a new and novel class of hemostatic agents that are electrically-based.}, number={19}, journal={LAB ON A CHIP}, author={Hardy, Elaissa T. and Wang, Yannan J. and Iyer, Sanathan and Mannino, Robert G. and Sakurai, Yumiko and Barker, Thomas H. and Chi, Taiyun and Youn, Yeojoon and Wang, Hua and Brown, Ashley C. and et al.}, year={2018}, month={Oct}, pages={2985–2993} }
 @misc{mihalko_brown_2018, title={Material Strategies for Modulating Epithelial to Mesenchymal Transitions}, volume={4}, ISSN={["2373-9878"]}, DOI={10.1021/acsbiomaterials.6b00751}, abstractNote={Epithelial to mesenchymal transitions (EMT) involve the phenotypic change of epithelial cells into fibroblast-like cells. This process is accompanied by the loss of cell-cell contacts, increased extracellular matrix (ECM) production, stress fiber alignment, and an increase in cell mobility. While essential for development and wound repair, EMT has also been recognized as a contributing factor to fibrotic diseases and cancer. Both chemical and mechanical cues, such as tumor necrosis factor alpha, NF-κB, Wnt, Notch, interleukin-8, metalloproteinase-3, ECM proteins, and ECM stiffness can determine the degree and duration of EMT events. Additionally, transforming growth factor beta is a primary driver of EMT and, interestingly, can be activated through cell-mediated mechanoactivation. In this review, we highlight recent findings demonstrating the contribution of mechanical stimuli, such as tissue and material stiffness, in driving EMT. We then highlight material strategies for controlling EMT events. Finally, we discuss drivers of the similar process of endothelial to mesenchymal transition (EndoMT) and corresponding material strategies for controlling EndoMT.}, number={4}, journal={ACS BIOMATERIALS SCIENCE & ENGINEERING}, author={Mihalko, Emily P. and Brown, Ashley C.}, year={2018}, month={Apr}, pages={1149–1161} }
 @article{joshi_nandi_chester_brown_muller_2018, title={Study of Poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAM) Microgel Particle Induced Deformations of Tissue-Mimicking Phantom by Ultrasound Stimulation}, volume={34}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.7b02801}, abstractNote={Poly(N-isopropylacrylamide) (pNIPAm) microgels (microgels) are colloidal particles that have been used extensively for biomedical applications. Typically, these particles are synthesized in the presence of an exogenous cross-linker, such as N,N'-methylenebis(acrylamide) (BIS); however, recent studies have demonstrated that pNIPAm microgels can be synthesized in the absence of an exogenous cross-linker, resulting in the formation of ultralow cross-linked (ULC) particles, which are highly deformable. Microgel deformability has been linked in certain cases to enhanced bioactivity when ULC microgels are used for the creation of biomimetic particles. We hypothesized that ultrasound stimulation of microgels would enhance particle deformation and that the degree of enhancement would negatively correlate with the degree of particle cross-linking. Here, we demonstrate in tissue-mimicking phantoms that using ultrasound insonification causes deformations of ULC microgel particles. Furthermore, the amount of deformation depends on the ultrasound excitation frequency and amplitude and on the concentration of ULC microgel particles. We observed that the amplitude of deformation increases with increasing ULC microgel particle concentration up to 2.5 mg/100 mL, but concentrations higher than 2.5 mg/100 mL result in reduced amount of deformation. In addition, we observed that the amplitude of deformation was significantly higher at 1 MHz insonification frequency. We also report that increasing the degree of microgel cross-linking reduces the magnitude of the deformation and increases the optimal concentration required to achieve the largest amount of deformation. Stimulated ULC microgel particle deformation has numerous potential biomedical applications, including enhancement of localized drug delivery and biomimetic activity. These results demonstrate the potential of ultrasound stimulation for such applications.}, number={4}, journal={LANGMUIR}, author={Joshi, Aditya and Nandi, Seema and Chester, Daniel and Brown, Ashley C. and Muller, Marie}, year={2018}, month={Jan}, pages={1457–1465} }
 @article{mihalko_huang_sproul_cheng_brown_2018, title={Targeted Treatment of Ischemic and Fibrotic Complications of Myocardial Infarction Using a Dual-Delivery Microgel Therapeutic}, volume={12}, ISSN={1936-0851 1936-086X}, url={http://dx.doi.org/10.1021/ACSNANO.8B01977}, DOI={10.1021/ACSNANO.8B01977}, abstractNote={Myocardial infarction (MI), commonly known as a heart attack, affects millions of people worldwide and results in significant death and disabilities. A major cause of MI is fibrin-rich thrombus formation that occludes the coronary arteries, blocking blood flow to the heart and causing fibrin deposition. In treating MI, re-establishing blood flow is critical. However, ischemia reperfusion (I/R) injury itself can also occur and contributes to cardiac fibrosis. Fibrin-specific poly( N-isopropylacrylamide) nanogels (FSNs) comprised of a core-shell colloidal hydrogel architecture are utilized in this study to design a dual-delivery system that simultaneously addresses the need to (1) re-establish blood flow and (2) inhibit cardiac fibrosis following I/R injury. These therapeutic needs are met by controlling the release of a fibrinolytic protein, tissue plasminogen activator (tPA), and a small molecule cell contractility inhibitor (Y-27632). In vitro, tPA and Y-27632-loaded FSNs rapidly degrade fibrin and decrease cardiac cell stress fiber formation and connective tissue growth factor expression, which are both upregulated in cardiac fibrosis. In vivo, FSNs localize to fibrin in injured heart tissue and, when loaded with tPA and Y-27632, showed significant improvement in left ventricular ejection fraction 2 and 4 weeks post-I/R as well as significantly decreased infarct size, α-smooth muscle actin expression, and connective tissue growth factor expression 4 weeks post-I/R. Together, these data demonstrate the feasibility of this targeted therapeutic strategy to improve cardiac function following MI.}, number={8}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Mihalko, Emily and Huang, Ke and Sproul, Erin and Cheng, Ke and Brown, Ashley C.}, year={2018}, month={Jul}, pages={7826–7837} }
 @article{tang_su_huang_dinh_wang_vandergriff_hensley_cores_allen_li_et al._2018, title={Targeted repair of heart injury by stem cells fused with platelet nanovesicles}, volume={2}, ISSN={["2157-846X"]}, url={https://europepmc.org/articles/PMC5976251}, DOI={10.1038/s41551-017-0182-x}, abstractNote={Stem cell transplantation, as used clinically, suffers from low retention and engraftment of the transplanted cells. Inspired by the ability of platelets to recruit stem cells to sites of injury on blood vessels, we hypothesized that platelets might enhance the vascular delivery of cardiac stem cells (CSCs) to sites of myocardial infarction injury. Here, we show that CSCs with platelet nanovesicles fused onto their surface membranes express platelet surface markers that are associated with platelet adhesion to injury sites. We also find that the modified CSCs selectively bind collagen-coated surfaces and endothelium-denuded rat aortas, and that in rat and porcine models of acute myocardial infarction the modified CSCs increase retention in the heart and reduce infarct size. Platelet-nanovesicle-fused CSCs thus possess the natural targeting and repairing ability of their parental cell types. This stem cell manipulation approach is fast, straightforward and safe, does not require genetic alteration of the cells, and should be generalizable to multiple cell types. The attachment of platelet nanovesicles to the surface of cardiac stem cells increases the retention of the cells delivered to the heart and reduces infarct size in rat and pig models of acute myocardial infarction.}, number={1}, journal={NATURE BIOMEDICAL ENGINEERING}, author={Tang, Junnan and Su, Teng and Huang, Ke and Dinh, Phuong-Uyen and Wang, Zegen and Vandergriff, Adam and Hensley, Michael T. and Cores, Jhon and Allen, Tyler and Li, Taosheng and et al.}, year={2018}, month={Jan}, pages={17–26} }
 @article{chester_kathard_nortey_nellenbach_brown_2018, title={Viscoelastic properties of microgel thin films control fibroblast modes of migration and pro-fibrotic responses}, volume={185}, ISSN={["1878-5905"]}, DOI={10.1016/j.biomaterials.2018.09.012}, abstractNote={Cell behavior is influenced by the biophysical properties of their microenvironments, and the linear elastic properties of substrates strongly influences adhesion, migration, and differentiation responses. Because most biological tissues exhibit non-linear elastic properties, there is a growing interest in understanding how the viscous component of materials and tissues influences cell fate. Here we describe the use of microgel thin films with controllable non-linear elastic properties for investigating the role of material loss tangent on cell adhesion, migration, and myofibroblastic differentiation, which have implications in fibrotic responses. Fibroblast modes of migration are dictated by film loss tangent; high loss tangent induced ROCK-mediated amoeboid migration while low loss tangent induced Rac-mediated mesenchymal cell migration. Low loss tangent films were also associated with higher levels of myofibroblastic differentiation. These findings have implications in fibrosis and indicate that slight changes in tissue viscoelasticity following injury could contribute to early initiation of fibrotic related responses.}, journal={BIOMATERIALS}, author={Chester, Daniel and Kathard, Rahul and Nortey, Jeremy and Nellenbach, Kimberly and Brown, Ashley C.}, year={2018}, month={Dec}, pages={371–382} }
 @article{nandi_brown_2017, title={Characterizing Cell Migration Within Three-dimensional In Vitro Wound Environments}, ISSN={["1940-087X"]}, DOI={10.3791/56099}, abstractNote={Currently, most in vitro models of wound healing, such as well-established scratch assays, involve studying cell migration and wound closure on two-dimensional surfaces. However, the physiological environment in which in vivo wound healing takes place is three-dimensional rather than two-dimensional. It is becoming increasingly clear that cell behavior differs greatly in two-dimensional vs. three-dimensional environments; therefore, there is a need for more physiologically relevant in vitro models for studying cell migration behaviors in wound closure. The method described herein allows for the study of cell migration in a three-dimensional model that better reflects physiological conditions than previously established two-dimensional scratch assays. The purpose of this model is to evaluate cell outgrowth via the examination of cell migration away from a spheroid body embedded within a fibrin matrix in the presence of pro- or anti-migratory factors. Using this method, cell outgrowth from the spheroid body in a three-dimensional matrix can be observed and is easily quantifiable over time via brightfield microscopy and analysis of spheroid body area. The effect of pro-migratory and/or inhibitory factors on cell migration can also be evaluated in this system. This method provides researchers with a simple method of analyzing cell migration in three-dimensional wound associated matrices in vitro, thus increasing the relevance of in vitro cell studies prior to the use of in vivo animal models.}, number={126}, journal={JOVE-JOURNAL OF VISUALIZED EXPERIMENTS}, author={Nandi, Seema and Brown, Ashley C.}, year={2017}, month={Aug} }
 @article{cao_nicosia_larouche_zhang_bachman_brown_holmgren_barker_2017, title={Detection of an Integrin-Binding Mechanoswitch within Fibronectin during Tissue Formation and Fibrosis}, volume={11}, ISSN={["1936-086X"]}, DOI={10.1021/acsnano.7b02755}, abstractNote={Fibronectin (Fn) is an extracellular matrix protein that orchestrates complex cell adhesion and signaling through cell surface integrin receptors during tissue development, remodeling, and disease, such as fibrosis. Fn is sensitive to mechanical forces in its tandem type III repeats, resulting in extensive molecular enlongation. As such, it has long been hypothesized that cell- and tissue-derived forces may activate an "integrin switch" within the critical integrin-binding ninth and 10th type III repeats-conferring differential integrin-binding specificity, leading to differential cell responses. Yet, no direct evidence exists to prove the hypothesis nor demonstrate the physiological existence of the switch. We report direct experimental evidence for the Fn integrin switch both in vitro and ex vivo using a scFv engineered to detect the transient, force-induced conformational change, representing an opportunity for detection and targeting of early molecular signatures of cell contractile forces in tissue repair and disease.}, number={7}, journal={ACS NANO}, author={Cao, Lizhi and Nicosia, John and Larouche, Jacqueline and Zhang, Yuanyuan and Bachman, Haylee and Brown, Ashley C. and Holmgren, Lars and Barker, Thomas H.}, year={2017}, month={Jul}, pages={7110–7117} }
 @article{nellenbach_brown_2017, title={Peptide Mimetic Drugs for Modulating Thrombosis and Hemostasis}, volume={78}, ISSN={["1098-2299"]}, DOI={10.1002/ddr.21407}, abstractNote={Preclinical Research}, number={6}, journal={DRUG DEVELOPMENT RESEARCH}, author={Nellenbach, Kimberly and Brown, Ashley C.}, year={2017}, month={Sep}, pages={236–244} }
 @article{myers_qiu_fay_tennenbaum_chester_cuadrado_sakurai_baek_tran_ciciliano_et al._2017, title={Single-platelet nanomechanics measured by high-throughput cytometry}, volume={16}, ISSN={["1476-4660"]}, DOI={10.1038/nmat4772}, abstractNote={Haemostasis occurs at sites of vascular injury, where flowing blood forms a clot, a dynamic and heterogeneous fibrin-based biomaterial. Paramount in the clot's capability to stem haemorrhage are its changing mechanical properties, the major drivers of which are the contractile forces exerted by platelets against the fibrin scaffold. However, how platelets transduce microenvironmental cues to mediate contraction and alter clot mechanics is unknown. This is clinically relevant, as overly softened and stiffened clots are associated with bleeding and thrombotic disorders. Here, we report a high-throughput hydrogel-based platelet-contraction cytometer that quantifies single-platelet contraction forces in different clot microenvironments. We also show that platelets, via the Rho/ROCK pathway, synergistically couple mechanical and biochemical inputs to mediate contraction. Moreover, highly contractile platelet subpopulations present in healthy controls are conspicuously absent in a subset of patients with undiagnosed bleeding disorders, and therefore may function as a clinical diagnostic biophysical biomarker.}, number={2}, journal={NATURE MATERIALS}, author={Myers, David R. and Qiu, Yongzhi and Fay, Meredith E. and Tennenbaum, Michael and Chester, Daniel and Cuadrado, Jonas and Sakurai, Yumiko and Baek, Jong and Tran, Reginald and Ciciliano, Jordan C. and et al.}, year={2017}, month={Feb}, pages={230–235} }
 @misc{chester_brown_2017, title={The role of biophysical properties of provisional matrix proteins in wound repair}, volume={60-61}, ISSN={["1569-1802"]}, DOI={10.1016/j.matbio.2016.08.004}, abstractNote={Wound healing is a complex, dynamic process required for maintaining homeostasis in an organism. Along with being controlled biochemically, wound healing is also controlled through the transduction of biophysical stimuli through cell interactions with the extracellular matrix (ECM). This review provides an overview of the ECM's role in the wound healing process and subsequently expands on the variety of roles biophysical phenomenon play.}, journal={MATRIX BIOLOGY}, author={Chester, Daniel and Brown, Ashley C.}, year={2017}, month={Jul}, pages={124–140} }
 @article{brown_hannan_timmins_fernandez_barker_guzzetta_2016, title={Fibrin Network Changes in Neonates after Cardiopulmonary Bypass}, volume={124}, ISSN={["1528-1175"]}, DOI={10.1097/aln.0000000000001058}, abstractNote={Background:Quantitative and qualitative differences in the hemostatic systems exist between neonates and adults, including the presence of “fetal” fibrinogen, a qualitatively dysfunctional form of fibrinogen that exists until 1 yr of age. The consequences of “fetal” fibrinogen on clot structure in neonates, particularly in the context of surgery-associated bleeding, have not been well characterized. Here, the authors examine the sequential changes in clotting components and resultant clot structure in a small sample of neonates undergoing cardiac surgery and cardiopulmonary bypass (CPB). Methods:Blood samples were collected from neonates (n = 10) before surgery, immediately after CPB, and after the transfusion of cryoprecipitate (i.e., adult fibrinogen component). Clots were formed from patient samples or purified neonatal and adult fibrinogen. Clot structure was analyzed using confocal microscopy. Results:Clots formed from plasma obtained after CPB and after transfusion were more porous than baseline clots. Analysis of clots formed from purified neonatal and adult fibrinogen demonstrated that at equivalent fibrinogen concentrations, neonatal clots lack three-dimensional structure, whereas adult clots were denser with significant three-dimensional structure. Clots formed from a combination of purified neonatal and adult fibrinogen were less homogenous than those formed from either purified adult or neonatal fibrinogen. Conclusions:The results of this study confirm that significant differences exist in clot structure between neonates and adults and that neonatal and adult fibrinogen may not integrate well. These findings suggest that differential treatment strategies for neonates should be pursued to reduce the demonstrated morbidity of blood product transfusion.}, number={5}, journal={ANESTHESIOLOGY}, author={Brown, Ashley C. and Hannan, Riley H. and Timmins, Lucas H. and Fernandez, Janet D. and Barker, Thomas H. and Guzzetta, Nina A.}, year={2016}, month={May}, pages={1021–1031} }
 @misc{nandi_brown_2016, title={Platelet-mimetic strategies for modulating the wound environment and inflammatory responses}, volume={241}, ISSN={["1535-3699"]}, DOI={10.1177/1535370216647126}, abstractNote={Platelets closely interface with the immune system to fight pathogens, target wound sites, and regulate tissue repair. Natural platelet levels within the body can be depleted for a variety of reasons, including excessive bleeding following traumatic injury, or diseases such as cancer and bacterial or viral infections. Platelet transfusions are commonly used to improve platelet count and hemostatic function in these cases, but transfusions can be complicated by the contamination risks and short storage life of donated platelets. Lyophilized platelets that can be freeze-dried and stored for longer periods of time and synthetic platelet-mimetic technologies that can enhance or replace the functions of natural platelets, while minimizing adverse immune responses have been explored as alternatives to transfusion. Synthetic platelets typically comprise nanoparticles surface-decorated with peptides or ligands to recreate specific biological characteristics of platelets, including targeting of wound and disease sites and facilitating platelet aggregation. Recent efforts in synthetic platelet design have additionally focused on matching platelet shape and mechanics to recreate the marginalization and clot contraction capabilities of natural platelets. The ability to specifically tune the properties of synthetic platelet-mimetic materials has shown utility in a variety of applications including hemostasis, drug delivery, and targeted delivery of cancer therapeutics.}, number={10}, journal={EXPERIMENTAL BIOLOGY AND MEDICINE}, author={Nandi, Seema and Brown, Ashley C.}, year={2016}, month={May}, pages={1138–1148} }
 @article{karumbaiah_enam_brown_saxena_betancur_barker_bellamkonda_2015, title={Chondroitin Sulfate Glycosaminoglycan Hydrogels Create Endogenous Niches for Neural Stem Cells}, volume={26}, ISSN={["1043-1802"]}, DOI={10.1021/acs.bioconjchem.5b00397}, abstractNote={Neural stem cells (NSCs) possess great potential for neural tissue repair after traumatic injuries to the central nervous system (CNS). However, poor survival and self-renewal of NSCs after injury severely limits its therapeutic potential. Sulfated chondroitin sulfate glycosaminoglycans (CS-GAGs) linked to CS proteoglycans (CSPGs) in the brain extracellular matrix (ECM) have the ability to bind and potentiate trophic factor efficacy, and promote NSC self-renewal in vivo. In this study, we investigated the potential of CS-GAG hydrogels composed of monosulfated CS-4 (CS-A), CS-6 (CS-C), and disulfated CS-4,6 (CS-E) CS-GAGs as NSC carriers, and their ability to create endogenous niches by enriching specific trophic factors to support NSC self-renewal. We demonstrate that CS-GAG hydrogel scaffolds showed minimal swelling and degradation over a period of 15 days in vitro, absorbing only 6.5 ± 0.019% of their initial weight, and showing no significant loss of mass during this period. Trophic factors FGF-2, BDNF, and IL10 bound with high affinity to CS-GAGs, and were significantly (p < 0.05) enriched in CS-GAG hydrogels when compared to unsulfated hyaluronic acid (HA) hydrogels. Dissociated rat subventricular zone (SVZ) NSCs when encapsulated in CS-GAG hydrogels demonstrated ∼88.5 ± 6.1% cell viability in vitro. Finally, rat neurospheres in CS-GAG hydrogels conditioned with the mitogen FGF-2 demonstrated significantly (p < 0.05) higher self-renewal when compared to neurospheres cultured in unconditioned hydrogels. Taken together, these findings demonstrate the ability of CS-GAG based hydrogels to regulate NSC self-renewal, and facilitate growth factor enrichment locally.}, number={12}, journal={BIOCONJUGATE CHEMISTRY}, author={Karumbaiah, Lohitash and Enam, Syed Faaiz and Brown, Ashley C. and Saxena, Tarun and Betancur, Martha I. and Barker, Thomas H. and Bellamkonda, Ravi V.}, year={2015}, month={Dec}, pages={2336–2349} }
 @article{brown_dysart_clarke_stabenfeldt_barker_2015, title={Integrin alpha 3 beta 1 binding to fibronectin is dependent on the ninth type III repeat}, volume={290}, DOI={10.1074/jbc.m115.656702}, abstractNote={Background: The fibronectin (Fn) ninth type III repeat can modulate integrin binding and resulting cell spreading. Results: Mutations within the Fn integrin binding domains affect integrin α3β1 binding. Conclusion: Integrin α3β1-fibronectin binding depends on the presence and spacing of the RGD and synergy sites within Fn. Significance: α3β1-fibronectin binding may modulate epithelial cell wound healing responses. Fibronectin (Fn) is a promiscuous ligand for numerous cell adhesion receptors or integrins. The vast majority of Fn-integrin interactions are mediated through the Fn Arg-Gly-Asp (RGD) motif located within the tenth type III repeat. In the case of integrins αIIbβ3 and α5β1, the integrin binds RGD and the synergy site (PHSRN) located within the adjacent ninth type III repeat. Prior work has shown that these synergy-dependent integrins are exquisitely sensitive to perturbations in the Fn integrin binding domain conformation. Our own prior studies of epithelial cell responses to recombinant fragments of the Fn integrin binding domain led us to hypothesize that integrin α3β1 binding may also be modulated by the synergy site. To explore this hypothesis, we created a variety of recombinant variants of the Fn integrin binding domain: (i) a previously reported (Leu → Pro) stabilizing mutant (FnIII9′10), (ii) an Arg to Ala synergy site mutation (FnIII9R→A10), (iii) a two-Gly (FnIII92G10) insertion, and (iv) a four-Gly (FNIII94G10) insertion in the interdomain linker region and used surface plasmon resonance to determine binding kinetics of integrin α3β1 to the Fn fragments. Integrin α3β1 had the highest affinity for FnIII9′10 and FnIII92G10. Mutation within the synergy site decreased integrin α3β1 binding 17-fold, and the four-Gly insertion decreased binding 39-fold compared with FnIII9′10. Cell attachment studies demonstrate that α3β1-mediated epithelial cell binding is greater on FnIII9′10 compared with the other fragments. These studies suggest that the presence and spacing of the RGD and synergy sites modulate integrin α3β1 binding to Fn.}, number={42}, journal={Journal of Biological Chemistry}, author={Brown, A. C. and Dysart, M. M. and Clarke, K. C. and Stabenfeldt, S. E. and Barker, T. H.}, year={2015}, pages={25534–25547} }
 @article{brown_baker_douglas_keating_alvarez-elizondo_botvinick_guthold_barker_2015, title={Molecular interference of fibrin's divalent polymerization mechanism enables modulation of multiscale material properties}, volume={49}, ISSN={0142-9612}, url={http://dx.doi.org/10.1016/J.BIOMATERIALS.2015.01.010}, DOI={10.1016/J.BIOMATERIALS.2015.01.010}, abstractNote={Protein based polymers provide an exciting and complex landscape for tunable natural biomaterials through modulation of molecular level interactions. Here we demonstrate the ability to modify protein polymer structural and mechanical properties at multiple length scales by molecular 'interference' of fibrin's native polymerization mechanism. We have previously reported that engagement of fibrin's polymerization 'hole b', also known as 'b-pockets', through PEGylated complementary 'knob B' mimics can increase fibrin network porosity but also, somewhat paradoxically, increase network stiffness. Here, we explore the possible mechanistic underpinning of this phenomenon through characterization of the effects of knob B-fibrin interaction at multiple length scales from molecular to bulk polymer. Despite its weak monovalent binding affinity for fibrin, addition of both knob B and PEGylated knob B at concentrations near the binding coefficient, Kd, increased fibrin network porosity, consistent with the reported role of knob B-hole b interactions in promoting lateral growth of fibrin fibers. Addition of PEGylated knob B decreases the extensibility of single fibrin fibers at concentrations near its Kd but increases extensibility of fibers at concentrations above its Kd. The data suggest this bimodal behavior is due to the individual contributions knob B, which decreases fiber extensibility, and PEG, which increase fiber extensibility. Taken together with laser trap-based microrheological and bulk rheological analyses of fibrin polymers, our data strongly suggests that hole b engagement increases in single fiber stiffness that translates to higher storage moduli of fibrin polymers despite their increased porosity. These data point to possible strategies for tuning fibrin polymer mechanical properties through modulation of single fiber mechanics.}, journal={Biomaterials}, publisher={Elsevier BV}, author={Brown, Ashley C. and Baker, Stephen R. and Douglas, Alison M. and Keating, Mark and Alvarez-Elizondo, Martha B. and Botvinick, Elliot L. and Guthold, Martin and Barker, Thomas H.}, year={2015}, month={May}, pages={27–36} }
 @article{bachman_brown_clarke_dhada_douglas_hansen_herman_hyatt_kodlekere_meng_et al._2015, title={Ultrasoft, highly deformable microgels}, volume={11}, ISSN={1744-683X 1744-6848}, url={http://dx.doi.org/10.1039/C5SM00047E}, DOI={10.1039/C5SM00047E}, abstractNote={Microgels are colloidally stable, hydrogel microparticles that have previously been used in a range of (soft) material applications due to their tunable mechanical and chemical properties. Most commonly, thermo and pH-responsive poly(N-isopropylacrylamide) (pNIPAm) microgels can be fabricated by precipitation polymerization in the presence of the co-monomer acrylic acid (AAc). Traditionally pNIPAm microgels are synthesized in the presence of a crosslinking agent, such as N,N'-methylenebisacrylamide (BIS), however, microgels can also be synthesized under 'crosslinker free' conditions. The resulting particles have extremely low (<0.5%), core-localized crosslinking resulting from rare chain transfer reactions. AFM nanoindentation of these ultralow crosslinked (ULC) particles indicate that they are soft relative to crosslinked microgels, with a Young's modulus of ∼10 kPa. Furthermore, ULC microgels are highly deformable as indicated by a high degree of spreading on glass surfaces and the ability to translocate through nanopores significantly smaller than the hydrodynamic diameter of the particles. The size and charge of ULCs can be easily modulated by altering reaction conditions, such as temperature, monomer, surfactant and initiator concentrations, and through the addition of co-monomers. Microgels based on the widely utilized, biocompatible polymer polyethylene glycol (PEG) can also be synthesized under crosslinker free conditions. Due to their softness and deformability, ULC microgels are a unique base material for a wide variety of biomedical applications including biomaterials for drug delivery and regenerative medicine.}, number={10}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={Bachman, Haylee and Brown, Ashley C. and Clarke, Kimberly C. and Dhada, Kabir S. and Douglas, Alison and Hansen, Caroline E. and Herman, Emily and Hyatt, John S. and Kodlekere, Purva and Meng, Zhiyong and et al.}, year={2015}, pages={2018–2028} }
 @article{kim_park_brown_lyon_2014, title={Direct observation of ligand-induced receptor dimerization with a bioresponsive hydrogel}, volume={4}, ISSN={2046-2069}, url={http://dx.doi.org/10.1039/C4RA13251C}, DOI={10.1039/C4RA13251C}, abstractNote={Multimerization of biomolecules is essential for biological function and thus there is a need for sensitive biochemical assays that determine whether a molecule associates with one or more other molecules in the context of biological function. In this contribution we demonstrate a simple yet versatile method for the identification of physiologically important receptor dimerization events induced by a ligand. Bioresponsive hydrogel microparticles (microgels) conjugated with a receptor, Glycoprotein Ibα (GPIbα), display large changes in optical (microscopic) appearance under conditions known for to promote thrombin-induced GPIbα dimerization. In support of X-ray crystal structures, we identify that one thrombin molecule associates with two GPIbα moieties, which may play a role in efficient hemostatic function by increasing local concentration of GPIbα on platelet surfaces. This microgel assay could provide a new way of studying important physiological and pathological mechanisms related to receptor dimerization and/or clustering.}, number={110}, journal={RSC Advances}, publisher={Royal Society of Chemistry (RSC)}, author={Kim, Jongseong and Park, Yongdoo and Brown, Ashley C. and Lyon, L. Andrew}, year={2014}, pages={65173–65175} }
 @article{baker_carson-brown_guthold_barker_2014, title={Fibrin Fibers: Blocking the B:B Knob-Pocket Interaction}, volume={106}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/J.BPJ.2013.11.3399}, DOI={10.1016/J.BPJ.2013.11.3399}, abstractNote={Fibrin clot formation has been studied to determine the mechanical properties of fibrin fibers modified by blocking the B-b knob-pocket interaction. Synthetic B-knob peptides AHRPYAAC or AHRPYAAC-Peg have been added to a fibrinogen solution to allow for binding to the b-pockets prior to clot formation. After fibrin clot formation, a combined atomic force microscopic (AFM)/optical microscopic technique was used to study the properties of individual fibrin fibers in buffer. Mechanical testing of fibers was done using the AFM to laterally stretch individual fibers suspended over 13.5μm wide groves in a transparent substrate. The optical microscope, located below the sample, was used to monitor the stretching process. We found that the density and lateral aggregation of fibers was hindered by blocking the b-pockets with the synthetic B-knobs.}, number={2}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Baker, Stephen and Carson-Brown, Ashley and Guthold, Martin and Barker, Thomas}, year={2014}, month={Jan}, pages={614a} }
 @article{brown_barker_2014, title={Fibrin-based biomaterials: Modulation of macroscopic properties through rational design at the molecular level}, volume={10}, ISSN={1742-7061}, url={http://dx.doi.org/10.1016/J.ACTBIO.2013.09.008}, DOI={10.1016/J.ACTBIO.2013.09.008}, abstractNote={Fibrinogen is one of the primary components of the coagulation cascade and rapidly forms an insoluble matrix following tissue injury. In addition to its important role in hemostasis, fibrin acts as a scaffold for tissue repair and provides important cues for directing cell phenotype following injury. Because of these properties and the ease of polymerization of the material, fibrin has been widely utilized as a biomaterial for over a century. Modifying the macroscopic properties of fibrin, such as elasticity and porosity, has been somewhat elusive until recently, yet with a molecular-level rational design approach it can now be somewhat easily modified through alterations of molecular interactions key to the protein's polymerization process. This review outlines the biochemistry of fibrin and discusses methods for modification of molecular interactions and their application to fibrin based biomaterials.}, number={4}, journal={Acta Biomaterialia}, publisher={Elsevier BV}, author={Brown, Ashley C. and Barker, Thomas H.}, year={2014}, month={Apr}, pages={1502–1514} }
 @article{bryksin_brown_baksh_finn_barker_2014, title={Learning from nature – Novel synthetic biology approaches for biomaterial design}, volume={10}, ISSN={1742-7061}, url={http://dx.doi.org/10.1016/J.ACTBIO.2014.01.019}, DOI={10.1016/J.ACTBIO.2014.01.019}, abstractNote={Many biomaterials constructed today are complex chemical structures that incorporate biologically active components derived from nature, but the field can still be said to be in its infancy. The need for materials that bring sophisticated properties of structure, dynamics and function to medical and non-medical applications will only grow. Increasing appreciation of the functionality of biological systems has caused biomaterials researchers to consider nature for design inspiration, and many examples exist of the use of biomolecular motifs. Yet evolution, nature's only engine for the creation of new designs, has been largely ignored by the biomaterials community. Molecular evolution is an emerging tool that enables one to apply nature's engineering principles to non-natural situations using variation and selection. The purpose of this review is to highlight the most recent advances in the use of molecular evolution in synthetic biology applications for biomaterial engineering, and to discuss some of the areas in which this approach may be successfully applied in the future.}, number={4}, journal={Acta Biomaterialia}, publisher={Elsevier BV}, author={Bryksin, Anton V. and Brown, Ashley C. and Baksh, Michael M. and Finn, M.G. and Barker, Thomas H.}, year={2014}, month={Apr}, pages={1761–1769} }
 @article{qiu_brown_myers_sakurai_mannino_tran_ahn_hardy_kee_kumar_et al._2014, title={Platelet mechanosensing of substrate stiffness during clot formation mediates adhesion, spreading, and activation}, volume={111}, ISSN={0027-8424 1091-6490}, url={http://dx.doi.org/10.1073/PNAS.1322917111}, DOI={10.1073/PNAS.1322917111}, abstractNote={Significance Platelets are cell fragments in the blood that initiate clot formation at the site of bleeding. Although the biological aspects of this process have been well characterized, whether platelets can detect and physiologically respond to the mechanical aspects of its local environment is unclear. Here, we show that platelets sense the stiffness of the underlying clot substrate, and increasing substrate stiffness increases platelet adhesion and spreading. Importantly, adhesion on stiffer substrates leads to higher levels of platelet activation. Mechanistically, we determined that Rac1, actin, and myosin activity mediate this process. This newfound capability of how platelets adjust their degree of activation based on the mechanical properties of their environment provides new insight into how clots are formed. As platelets aggregate and activate at the site of vascular injury to stem bleeding, they are subjected to a myriad of biochemical and biophysical signals and cues. As clot formation ensues, platelets interact with polymerizing fibrin scaffolds, exposing platelets to a large range of mechanical microenvironments. Here, we show for the first time (to our knowledge) that platelets, which are anucleate cellular fragments, sense microenvironmental mechanical properties, such as substrate stiffness, and transduce those cues into differential biological signals. Specifically, as platelets mechanosense the stiffness of the underlying fibrin/fibrinogen substrate, increasing substrate stiffness leads to increased platelet adhesion and spreading. Importantly, adhesion on stiffer substrates also leads to higher levels of platelet activation, as measured by integrin αIIbβ3 activation, α-granule secretion, and procoagulant activity. Mechanistically, we determined that Rac1 and actomyosin activity mediate substrate stiffness-dependent platelet adhesion, spreading, and activation to different degrees. This capability of platelets to mechanosense microenvironmental cues in a growing thrombus or hemostatic plug and then mechanotransduce those cues into differential levels of platelet adhesion, spreading, and activation provides biophysical insight into the underlying mechanisms of platelet aggregation and platelet activation heterogeneity during thrombus formation.}, number={40}, journal={Proceedings of the National Academy of Sciences}, publisher={Proceedings of the National Academy of Sciences}, author={Qiu, Yongzhi and Brown, Ashley C. and Myers, David R. and Sakurai, Yumiko and Mannino, Robert G. and Tran, Reginald and Ahn, Byungwook and Hardy, Elaissa T. and Kee, Matthew F. and Kumar, Sanjay and et al.}, year={2014}, month={Oct}, pages={14430–14435} }
 @article{brown_stabenfeldt_ahn_hannan_dhada_herman_stefanelli_guzzetta_alexeev_lam_et al._2014, title={Ultrasoft microgels displaying emergent platelet-like behaviours}, volume={13}, ISSN={1476-1122 1476-4660}, url={http://dx.doi.org/10.1038/NMAT4066}, DOI={10.1038/NMAT4066}, abstractNote={Efforts to create platelet-like structures for the augmentation of haemostasis have focused solely on recapitulating aspects of platelet adhesion; more complex platelet behaviours such as clot contraction are assumed to be inaccessible to synthetic systems. Here, we report the creation of fully synthetic platelet-like particles (PLPs) that augment clotting in vitro under physiological flow conditions and achieve wound-triggered haemostasis and decreased bleeding times in vivo in a traumatic injury model. PLPs were synthesized by combining highly deformable microgel particles with molecular-recognition motifs identified through directed evolution. In vitro and in silico analyses demonstrate that PLPs actively collapse fibrin networks, an emergent behaviour that mimics in vivo clot contraction. Mechanistically, clot collapse is intimately linked to the unique deformability and affinity of PLPs for fibrin fibres, as evidenced by dissipative particle dynamics simulations. Our findings should inform the future design of a broader class of dynamic, biosynthetic composite materials.}, number={12}, journal={Nature Materials}, publisher={Springer Science and Business Media LLC}, author={Brown, Ashley C. and Stabenfeldt, Sarah E. and Ahn, Byungwook and Hannan, Riley T. and Dhada, Kabir S. and Herman, Emily S. and Stefanelli, Victoria and Guzzetta, Nina and Alexeev, Alexander and Lam, Wilbur A. and et al.}, year={2014}, month={Sep}, pages={1108–1114} }
 @article{clarke_douglas_brown_barker_lyon_2013, title={Colloid-matrix assemblies in regenerative medicine}, volume={18}, ISSN={1359-0294}, url={http://dx.doi.org/10.1016/J.COCIS.2013.07.004}, DOI={10.1016/J.COCIS.2013.07.004}, abstractNote={The development of tissue engineering scaffolds has focused on mimicking the natural biochemical and biophysical environment of the extracellular matrix (ECM). In this review, we describe a variety of strategies aimed at reproducing and also simplifying the ECM. Despite the progress that has been made, the degree of complexity that needs to be incorporated into these scaffolds is still not known. We begin by describing the ECM and its biological functions followed by outlining current efforts to engineer ECMs with both natural and synthetic polymers. We then focus on colloidal particles as potential artificial ECM components that could increase the complexity as modular building blocks. Drawing from examples from the literature we present the broad utility of colloids and describe how these applications could be useful in the development of ECM mimetic systems.}, number={5}, journal={Current Opinion in Colloid & Interface Science}, publisher={Elsevier BV}, author={Clarke, Kimberly C. and Douglas, Alison M. and Brown, Ashley C. and Barker, Thomas H. and Lyon, L. Andrew}, year={2013}, month={Oct}, pages={393–405} }
 @article{brown_fiore_sulchek_barker_2013, title={Physical and chemical microenvironmental cues orthogonally control the degree and duration of fibrosis-associated epithelial-to-mesenchymal transitions}, volume={229}, ISSN={0022-3417}, url={http://dx.doi.org/10.1002/path.4114}, DOI={10.1002/path.4114}, abstractNote={Increased tissue stiffness and epithelial‐to‐mesenchymal transitions (EMTs) are two seemingly discrete hallmarks of fibrotic diseases. Despite recent findings highlighting the influence of tissue mechanical properties on cell phenotype, it remains unclear what role increased tissue stiffness has in the regulation of previously reported fibronectin‐mediated EMTs associated with pulmonary fibrosis. Nano‐indentation testing of lung interstitial spaces showed that in vivo cell‐level Young's moduli increase with the onset of fibrosis from ∼2 to ∼17 kPa. In vitro, we found that stiff, but not soft, fibronectin substrates induce EMT, a response dependent on cell contraction‐mediated integrin activation of TGFβ. Activation or suppression of cell contractility with exogenous factors was sufficient to overcome the effect of substrate stiffness. Pulse‐chase experiments indicate that the effect of cell contractility is dose‐ and time‐dependent. In response to low levels of TGFβ on soft surfaces, either added exogenously or produced through thrombin‐induced contraction, cells will initiate the EMT programme, but upon removal revert to an epithelial phenotype. These results identify matrix stiffness and/or cell contractility as critical targets for novel therapeutics for fibrotic diseases.}, number={1}, journal={The Journal of Pathology}, publisher={Wiley}, author={Brown, Ashley C and Fiore, Vincent F and Sulchek, Todd A and Barker, Thomas H}, year={2013}, month={Jan}, pages={25–35} }
 @article{baker_carson brown_barker_guthold_2013, title={The Mechanical Properties of Modified Fibrin Fibers: Blocking the B-b Knob-Pocket Interaction}, volume={104}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/j.bpj.2012.11.2831}, DOI={10.1016/j.bpj.2012.11.2831}, abstractNote={Fibrin clot formation has been studied to determine the mechanical properties of fibrin fibers modified by blocking the B-b knob-pocket interaction. Synthetic B-knob peptides AHRPYAAC or AHRPYAAC-Peg have been added to a fibrinogen solution to allow for binding to the b-pockets prior to clot formation. After fibrin clot formation, a combined atomic force microscopic (AFM)/optical microscopic technique was used to study the properties of individual fibrin fibers in buffer. Mechanical testing of fibers was done using the AFM to laterally stretch individual fibers suspended over 13.5μm wide groves in a transparent substrate. The optical microscope, located below the sample, was used to monitor the stretching process. We found that the density and lateral aggregation of fibers was hindered by blocking the b-pockets with the synthetic B-knobs. Fibrin fibers modified with the synthetic peptide AHRPYAAC-Peg were found to stretch to 2.27 times their original length before rupturing compared to unmodified fibrin fibers which were found to stretch to 2.47 times their original length. From these results it is expected that synthetic B-knob concentration impacts the mechanical properties of modified fibrin fibers. The binding constants for AHRPYAAC were found to be 30.3 μM and 80.1 μM while the binding constants for AHRPYAAC-Peg were found to be 1.75 mM and 57.2 μM.}, number={2}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Baker, Stephen and Carson Brown, Ashley and Barker, Thomas and Guthold, Martin}, year={2013}, month={Jan}, pages={512a–513a} }
 @article{markowski_brown_barker_2012, title={Directing epithelial to mesenchymal transition through engineered microenvironments displaying orthogonal adhesive and mechanical cues}, volume={100A}, ISSN={1549-3296}, url={http://dx.doi.org/10.1002/jbm.a.34068}, DOI={10.1002/jbm.a.34068}, abstractNote={Cell interactions with their extracellular matrix (ECM) microenvironments play a major role in directing cellular processes that can drive wound healing and tissue regeneration but, if uncontrolled, lead to pathological progression. One such process, epithelial to mesenchymal transition (EMT), if finely controlled could have significant potential in regenerative medicine approaches. Despite recent findings that highlight the influence of biochemical and mechanical properties of the ECM on EMT, it is still unclear how these two orthogonal cues act synergistically to control epithelial cell phenotype. Here, we cultured lung epithelial cells on combinations of different mutants of fibronectin's cell binding domain that preferentially engage specific integrins and substrates of varying stiffness. Our results suggest that while stiff substrates induce spontaneous EMT, this response can be overcome by with fragments of fibronectin that support α3 and α5 integrin engagement. Furthermore, we found that substrate-induced EMT correlates with transforming growth factor beta activation by resident epithelial cells and is dependent on Rho/ROCK signaling. Suppressing cell-contractility was sufficient to maintain an epithelial phenotype. Our results suggest that integrin-specific engagement of fibronectin adhesive domains and the mechanics of the ECM act synergistically to direct EMT.}, number={8}, journal={Journal of Biomedical Materials Research Part A}, publisher={Wiley}, author={Markowski, Marilyn C. and Brown, Ashley C. and Barker, Thomas H.}, year={2012}, month={Aug}, pages={2119–2127} }
 @article{park_brown_difeo_barker_lu_2010, title={Continuously perfused, non-cross-contaminating microfluidic chamber array for studying cellular responses to orthogonal combinations of matrix and soluble signals}, volume={10}, ISSN={1473-0197 1473-0189}, url={http://dx.doi.org/10.1039/b919294h}, DOI={10.1039/b919294h}, abstractNote={We present a microfluidic cell culture array with unique versatility and parallelization for experimental trials requiring perfusion cultures. Specifically, we realize a rectangular chamber array in a PDMS device with three attributes: (i) continuous perfusion; (ii) flow paths that forbid cross-chamber contamination; and (iii) chamber shielding from direct perfusion to minimize shear-induced cell behaviour. These attributes are made possible by a bridge-and-underpass architecture, where flow streams travel vertically to pass over (or under) channels and on-chip valves. The array is also designed for considerable versatility, providing subarray, row, column, or single chamber addressing. It allows for incubation with adsorbed molecules, perfusion of differing media, seeding or extraction of cells, and assay staining. We use the device to characterize different phenotypes of alveolar epithelial type II (ATII) cells, particularly the extent of epithelial-to-mesenchymal transition (EMT), a highly suspected pathway in tissue regeneration and fibrosis. Cells are cultured on combinations of matrix proteins (fibronectin or laminin by row) and soluble signals (with or without transforming growth factor-beta1 by column) with two repeats per chip. Fluorescent assays are performed in the array to assess viability, cytoskeletal organization, and cell-cell junction formation. Assay and morphological data are used to tease-out effects of cues driving each phenotype, confirming this as an effective and versatile combinatorial screening platform.}, number={5}, journal={Lab Chip}, publisher={Royal Society of Chemistry (RSC)}, author={Park, Edward S. and Brown, Ashley C. and DiFeo, Michael A. and Barker, Thomas H. and Lu, Hang}, year={2010}, pages={571–580} }