(95z) Incorporating Fibrinogen into Photopolymerizable Hydrogel Chondrocyte Carriers for Cartilage Tissue Engineering

Fibrinogen is a key component in the blood clotting process and can be polymerized in vitro to form a hydrogel called fibrin. Encapsulated chondrocytes have reacted favorably to fibrin gels in cartilage tissue engineering applications in the past¹, but fibrin gels are weak, and gel properties are very difficult to reproduce. Hydrogels synthesized from photopolymerizable, dimethacrylated poly(ethylene glycol) (PEG-DM) macromonomers can be reliably tuned to control numerous gel properties². In this study, various hydrogels were synthesized from combinations of PEG-DM and fibrinogen components. Many of these hydrogels were impractical as injectable chondrocyte carriers, due to diffusional time constraints or aggregation of fibrinogen in solution. Chondrocyte encapsulation studies showed little effect on extracellular matrix production when unmodified, aggregated fibrinogen was co-encapsulated at varying levels. It is likely that fibrinogen aggregates cannot diffuse through the gel network, or that encapsulated cells cannot recognize them. In order to decrease this aggregation effect, monomethacrylated PEG-N-hydroxy succinimide was synthesized and reacted with random free amine groups on fibrinogen molecules. The resulting modified fibrinogen did not aggregate in PEG-DM solutions, and contained pendant methacrylate groups that could be photopolymerized with PEG-DM to form a crosslinked network with a homogeneous distribution of fibrinogen.

1. Sims CD, Butler PE, Cao YL, Casanova R, Randolph MA, Black A, Vacanti CA, Yaremchuk MJ. Tissue engineered neocartilage using plasma derived polymer substrates and chondrocytes. PLASTIC AND RECONSTRUCTIVE SURGERY 1998;101(6):1580-5.

2. Bryant SJ, Anseth KS. Hydrogel properties influence ECM production by chondrocytes photoencapsulated in poly(ethylene glycol) hydrogels. Journal of Biomedical Materials Research 2002;59(1):63-72.