@article{maturavongsadit_narayanan_chansoria_shirwaiker_benhabbour_2021, title={Cell-Laden Nanocellulose/Chitosan-Based Bioinks for 3D Bioprinting and Enhanced Osteogenic Cell Differentiation}, volume={4}, ISSN={["2576-6422"]}, DOI={10.1021/acsabm.0c01108}, abstractNote={3D bioprinting has recently emerged as a very useful tool in tissue engineering and regenerative medicine. However, developing suitable bioinks to fabricate specific tissue constructs remains a challenging task. Herein, we report on a nanocellulose/chitosan-based bioink, which is compatible with a 3D extrusion-based bioprinting technology, to design and engineer constructs for bone tissue engineering and regeneration applications. Bioinks were prepared using thermogelling chitosan, glycerophosphate, hydroxyethyl cellulose, and cellulose nanocrystals (CNCs). Formulations were optimized by varying the concentrations of glycerophosphate (80-300 mM), hydroxyethyl cellulose (0-0.5 mg/mL), and CNCs (0-2% w/v) to promote fast gelation kinetics (<7 s) at 37 °C and retain the shape integrity of constructs post 3D bioprinting. We investigated the effect of CNCs and pre-osteoblast cells (MC3T3-E1) on the rheological properties of bioinks, bioink printability, and mechanical properties of bioprinted scaffolds. We demonstrate that the addition of CNCs and cells (5 million cells/mL) significantly improved the viscosity of bioinks and the mechanical properties of chitosan scaffolds post-fabrication. The bioinks were biocompatible and printable at an optimized range of printing pressures (12-20 kPa) that did not compromise cell viability. The presence of CNCs promoted greater osteogenesis of MC3T3-E1 cells in chitosan scaffolds as shown by the upregulation of alkaline phosphatase activity, higher calcium mineralization, and extracellular matrix formation. The versatility of this CNCs-incorporated chitosan hydrogel makes it attractive as a bioink for 3D bioprinting to engineer scaffolds for bone tissue engineering and other therapeutic applications.}, number={3}, journal={ACS APPLIED BIO MATERIALS}, author={Maturavongsadit, Panita and Narayanan, Lokesh Karthik and Chansoria, Parth and Shirwaiker, Rohan and Benhabbour, S. Rahima}, year={2021}, month={Mar}, pages={2342–2353} }
 @article{chansoria_narayanan_wood_alvarado_lin_shirwaiker_2020, title={Effects of Autoclaving, EtOH, and UV Sterilization on the Chemical, Mechanical, Printability, and Biocompatibility Characteristics of Alginate}, volume={6}, ISSN={["2373-9878"]}, DOI={10.1021/acsbiomaterials.0c00806}, abstractNote={Sterilization is a necessary step during the processing of biomaterials, but it can affect the materials' functional characteristics. This study characterizes the effects of three commonly used sterilization processes-autoclaving (heat-based), ethanol (EtOH; chemical-based), and ultraviolet (UV; radiation-based)-on the chemical, mechanical, printability, and biocompatibility properties of alginate, a widely used biopolymer for drug delivery, tissue engineering, and other biomedical applications. Sterility assessment tests showed that autoclaving was effective against Gram-positive and Gram-negative bacteria at loads up to 108 CFU/mL, while EtOH was the least effective. Nuclear magnetic-resonance spectroscopy showed that the sterilization processes did not affect the monomeric content in the alginate solutions. The differences in compressive stiffness of the three sterilized hydrogels were also not significant. However, autoclaving significantly reduced the molecular weight and polydispersity index, as determined via gel permeation chromatography, as well as the dynamic viscosity of alginate. Printability analyses showed that the sterilization process as well as the extrusion pressure and speed affected the number of discontinuities and spreading ratio in printed and cross-linked strands. Finally, human adipose-derived stem cells demonstrated over 90% viability in all sterilized hydrogels over 7 days, but the differences in cellular metabolic activity in the three groups were significant. Taken together, the autoclaving process, while demonstrating broad spectrum sterility effectiveness, also resulted in most notable changes in alginate's key properties. In addition to the specific results with the three sterilization processes and alginate, this study serves as a roadmap to characterize the interrelationships between sterilization processes, fundamental chemical properties, and resulting functional characteristics and processability of hydrogels.}, number={9}, journal={ACS BIOMATERIALS SCIENCE & ENGINEERING}, author={Chansoria, Parth and Narayanan, Lokesh Karthik and Wood, Madison and Alvarado, Claudia and Lin, Annie and Shirwaiker, Rohan A.}, year={2020}, month={Sep}, pages={5191–5201} }
 @article{chansoria_narayanan_schuchard_shirwaiker_2019, title={Ultrasound-assisted biofabrication and bioprinting of preferentially aligned three-dimensional cellular constructs}, volume={11}, ISSN={["1758-5090"]}, DOI={10.1088/1758-5090/ab15cf}, abstractNote={Abstract}, number={3}, journal={BIOFABRICATION}, author={Chansoria, Parth and Narayanan, Lokesh Karthik and Schuchard, Karl and Shirwaiker, Rohan}, year={2019}, month={Jul} }
 @article{narayanan_thompson_shirwaiker_starly_2018, title={Label free process monitoring of 3D bioprinted engineered constructs via dielectric impedance spectroscopy}, volume={10}, ISSN={["1758-5090"]}, DOI={10.1088/1758-5090/aaccbf}, abstractNote={Biofabrication processes can affect biological quality attributes of encapsulated cells within constructs. Currently, assessment of the fabricated constructs is performed offline by subjecting the constructs to destructive assays that require staining and sectioning. This drawback limits the translation of biofabrication processes to industrial practice. In this work, we investigate the dielectric response of viable cells encapsulated in bioprinted 3D hydrogel constructs to an applied alternating electric field as a label-free non-destructive monitoring approach. The relationship between β-dispersion parameters (permittivity change—Δε, Cole–Cole slope factor—α, critical polarization frequency—fc) over the frequency spectrum and critical cellular quality attributes are investigated. Results show that alginate constructs containing a higher number of viable cells (human adipose derived stem cells—hASC and osteosarcoma cell line—MG63) were characterized by significantly higher Δε and α (both p < 0.05). When extended to bioprinting, results showed that changes in hASC proliferation and viability in response to changes in critical bioprinting parameters (extrusion pressure, temperature, processing time) significantly affected ∆ε, α, and fc. We also demonstrated monitoring of hASC distribution after bioprinting and changes in proliferation over time across the cross-section of a bioprinted medial knee meniscus construct. The trends in ∆ε over time were in agreement with the alamarBlue assay results for the whole construct, but this measurement approach provided a localized readout on the status of encapsulated cells. The findings of this study support the use of dielectric impedance spectroscopy as a label-free and non-destructive method to characterize the critical quality attributes of bioprinted constructs.}, number={3}, journal={BIOFABRICATION}, author={Narayanan, Lokesh Karthik and Thompson, Trevor L. and Shirwaiker, Rohan A. and Starly, Binil}, year={2018}, month={Jul} }
 @inproceedings{narayanan_thompson_bhat_starly_shirwaiker_2017, title={Investigating dielectric impedance spectroscopy as a non-destructive quality assessment tool for 3D cellular constructs}, DOI={10.1115/msec2017-2725}, abstractNote={In any three dimensional (3D) biofabrication process, assessing critical biological quality attributes of 3D constructs such as viable cell number, cell distribution and metabolic activity is critical to determine the suitability and success of the process. One major limitation in current state-of-the-art is the lack of appropriate methods to monitor these quality attributes in situ in a non-destructive, label-free manner. In this study, we investigate the feasibility of using dielectric impedance spectroscopy to address this gap. We first measured the relative permittivity of 3D alginate constructs with four different concentrations of encapsulated MG63 cells (1–6.5 million cells/mL) and found them to be statistically significantly different (p < 0.05). Within the tested range, the relationship between cell concentration and relative permittivity was noted to be linear (R2 = 0.986). Furthermore, we characterized the β-dispersion parameters for MG63-encapsulated in alginate (6.5 million cells/mL). These results demonstrate that dielectric impedance spectroscopy can be used to monitor critical quality attributes of cell-encapsulated 3D constructs. Owing to the measurement efficiency and non-destructive mode of testing, this method has tremendous potential as an in-process quality control tool for 3D biofabrication processes and the long-term monitoring of cell-encapsulated 3D constructs.}, booktitle={Proceedings of the ASME 12th International Manufacturing Science and Engineering Conference - 2017, vol 4}, author={Narayanan, L. K. and Thompson, T. L. and Bhat, A. and Starly, Binil and Shirwaiker, Rohan}, year={2017} }
 @article{narayanan_huebner_fisher_spang_starly_shirwaiker_2016, title={3D-Bioprinting of Polylactic Acid (PLA) Nanofiber–Alginate Hydrogel Bioink Containing Human Adipose-Derived Stem Cells}, volume={2}, ISSN={2373-9878 2373-9878}, url={http://dx.doi.org/10.1021/ACSBIOMATERIALS.6B00196}, DOI={10.1021/acsbiomaterials.6b00196}, abstractNote={Bioinks play a central role in 3D-bioprinting by providing the supporting environment within which encapsulated cells can endure the stresses encountered during the digitally driven fabrication process and continue to mature, proliferate, and eventually form extracellular matrix (ECM). In order to be most effective, it is important that bioprinted constructs recapitulate the native tissue milieu as closely as possible. As such, musculoskeletal soft tissue constructs can benefit from bioinks that mimic their nanofibrous matrix constitution, which is also critical to their function. This study focuses on the development and proof-of-concept assessment of a fibrous bioink composed of alginate hydrogel, polylactic acid nanofibers, and human adipose-derived stem cells (hASC) for bioprinting such tissue constructs. First, hASC proliferation and viability were assessed in 3D-bioplotted strands over 16 days in vitro. Then, a human medial knee meniscus digitally modeled using magnetic resonance images was bioprinted and evaluated over 8 weeks in vitro. Results show that the nanofiber-reinforced bioink allowed higher levels of cell proliferation within bioprinted strands, with a peak at day 7, while still maintaining a vast majority of viable cells at day 16. The cell metabolic activity on day 7 was 28.5% higher in this bioink compared to the bioink without nanofibers. Histology of the bioprinted meniscus at both 4 and 8 weeks showed 54% and 147% higher cell density, respectively, in external versus internal regions of the construct. The presence of collagen and proteoglycans was also noted in areas surrounding the hASC, indicating ECM secretion and chondrogenic differentiation.}, number={10}, journal={ACS Biomaterials Science & Engineering}, publisher={American Chemical Society (ACS)}, author={Narayanan, Lokesh Karthik and Huebner, Pedro and Fisher, Matthew B. and Spang, Jeffrey T. and Starly, Binil and Shirwaiker, Rohan A.}, year={2016}, month={Jul}, pages={1732–1742} }
 @article{johnson_sheshadri_ketchum_narayanan_weinberger_shirwaiker_2016, title={In vitro characterization of design and compressive properties of 3D-biofabricated/decellularized hybrid grafts for tracheal tissue engineering}, volume={59}, ISSN={["1878-0180"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84962441476&partnerID=MN8TOARS}, DOI={10.1016/j.jmbbm.2016.03.024}, abstractNote={Infection or damage to the trachea, a thin walled and cartilage reinforced conduit that connects the pharynx and larynx to the lungs, leads to serious respiratory medical conditions which can often prove fatal. Current clinical strategies for complex tracheal reconstruction are of limited availability and efficacy, but tissue engineering and regenerative medicine approaches may provide viable alternatives. In this study, we have developed a new “hybrid graft” approach that utilizes decellularized tracheal tissue along with a resorbable polymer scaffold, and holds promise for potential clinical applications. First, we evaluated the effect of our decellularization process on the compression properties of porcine tracheal segments, and noted approximately 63% decrease in resistance to compression following decellularization. Next we developed four C-shape scaffold designs by varying the base geometry and thickness, and fabricated polycaprolactone scaffolds using a combination of 3D-Bioplotting and thermally-assisted forming. All scaffolds designs were evaluated in vitro under three different environmental testing conditions to determine the design that offered the best resistance to compression. These were further studied to determine the effect of gamma radiation sterilization and cyclic compression loading. Finally, hybrid grafts were developed by securing these optimal design scaffolds to decellularized tracheal segments and evaluated in vitro under physiological testing conditions. Results show that the resistance to compression offered by the hybrid grafts created using gamma radiation sterilized scaffolds was comparable to that of fresh tracheal segments. Given that current clinical attempts at tracheal transplantation using decellularized tissue have been fraught with luminal collapse and complications, our data support the possibility that future embodiments using a hybrid graft approach may reduce the need for intraluminal stenting in tracheal transplant recipients.}, journal={JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS}, author={Johnson, Christopher and Sheshadri, Priyanka and Ketchum, Jessica M. and Narayanan, Lokesh K. and Weinberger, Paul M. and Shirwaiker, Rohan A.}, year={2016}, month={Jun}, pages={572–585} }