The biocompatibility of PluronicF127 fibrinogen-based hydrogels.

Our research is focused on the design of hydrogel biomaterials that can be used for 3-D cell encapsulation and tissue engineering. In this study, our goal was to engineer a temperature-responsive biomaterial to possess bioactive properties using polymer and protein chemistry, and at the same time provide the biomaterial with susceptibility to cell-mediated remodeling. Toward this goal, we developed a biomimetic material that can harness the bioactive properties of fibrinogen and the unique structural properties of PluronicF127. PluronicF127 is a synthetic block copolymer that exhibits reverse thermal gelation (RTG) in response to small changes in ambient temperature. We conjugated fibrinogen to Pluronic)F127 to create a biosynthetic precursor with tunable physicochemical properties based on the relationship between the two constituents. A hydrogel matrix was formed from the fibrinogen-F127 adducts by free-radical polymerization using light activation (photo-polymerization). These materials displayed a reversible temperature-induced physical sol-gel transition and an irreversible light-activated chemical cross-linking. The susceptibility of this hydrogel biomaterial to protease degradation and consequent cell-mediated remodeling was controlled by the PluronicF127 constituent. The protein-based material also conveyed inductive signals to cells through bioactive sites on the fibrinogen backbone, as well as through structural properties such as the matrix modulus. We apply these materials as a tissue engineering hydrogel scaffold for 3-D in vitro culture of dermal fibroblasts in order to gain a better understanding of how the material bioactivity and matrix properties can independently affect cell morphology and remodeling.