@article{nalband_sarker_khan_freytes_2023, title={Characterization and biological evaluation of a novel flavonoid-collagen antioxidant hydrogel with cytoprotective properties}, volume={9}, ISSN={["1552-4981"]}, DOI={10.1002/jbm.b.35321}, abstractNote={Reactive oxygen species (ROS) play a critical and important role during wound healing but excess ROS at the wound site can lead to cellular damage and sub-optimal healing. Minimizing oxidative damage to the wound site and any supplemental therapeutic cells can be achieved by delivering exogenous antioxidants. Collagen hydrogels are ideal wound care materials due to their biocompatibility, high water content, and porous, three-dimensional architecture. Yet, they lack the inherent antioxidant activity that could help mitigate excess ROS at a wound site. This work formulates and evaluates the in vitro biocompatibility and antioxidant capabilities of collagen-fibroblast hydrogels combined with the polyphenolic antioxidant luteolin. Collagen solutions mixed with luteolin readily assembled into robust hydrogels with increasing gel strength due to increasing concentrations of luteolin. SEM images confirmed a mean pore size of 2.2 μm and a drastically different macromolecular ultrastructure with extensive fine crosslinking relative to collagen. Adequate cell viability and metabolic activity of dermal fibroblasts cultured within the gels were measured across all formulations, resulting in higher antioxidant activity and more than double the protection to cells from oxidative damage than traditional collagen hydrogels. Given these results, luteolin-collagen hydrogels demonstrate the potential for superior wound-healing properties when compared to collagen alone.}, journal={JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS}, author={Nalband, Danielle M. and Sarker, Prottasha and Khan, Saad A. and Freytes, Donald O.}, year={2023}, month={Sep} }
 @article{sarker_nalband_freytes_rojas_khan_2022, title={High-Axial-Aspect Tannic Acid Microparticles Facilitate Gelation and Injectability of Collagen-Based Hydrogels}, volume={10}, ISSN={["1526-4602"]}, url={https://doi.org/10.1021/acs.biomac.2c00916}, DOI={10.1021/acs.biomac.2c00916}, abstractNote={Injectable collagen-based hydrogels offer great promise for tissue engineering and regeneration, but their use is limited by poor mechanical strength. Herein, we incorporate tannic acid (TA) to tailor the rheology of the corresponding hydrogels while simultaneously adding the therapeutic benefits inherent to this polyphenolic component. TA in the solution form and needle-shaped TA microparticles are combined with collagen and the respective systems studied for their time-dependent sol-gel transitions (from storage to body temperatures, 4-37 °C) as a function of TA concentration. Compared to systems incorporating TA microparticles, those with dissolved TA, applied at a similar concentration, generate a less significant enhancement of the elastic modulus. Premature gelation at a low temperature and associated colloidal arrest of the system are proposed as a main factor explaining this limited performance. A higher yield stress (elastic stress method) is determined for systems loaded with TA microparticles compared to the system with dissolved TA. These results are interpreted in terms of the underlying interactions of TA with collagen, as probed by spectroscopy and isothermal titration calorimetry. Importantly, hydrogels containing TA microparticles show high cell viability (human dermal fibroblasts) and comparative cellular activity relative to the collagen-only hydrogel. Overall, composite hydrogels incorporating TA microparticles demonstrate a new, simple, and better-performance alternative to cell culturing and difficult implantation scenarios.}, journal={BIOMACROMOLECULES}, author={Sarker, Prottasha and Nalband, Danielle M. and Freytes, Donald O. and Rojas, Orlando J. and Khan, Saad A.}, year={2022}, month={Oct} }