@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{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{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} }
 @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{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{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{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{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} }