Disulfide-crosslinked hyaluronan-gelatin hydrogel films: a covalent mimic of the extracellular matrix for in vitro cell growth.

A new disulfide crosslinking method was developed for the preparation of blended hyaluronan (HA)-gelatin hydrogels to form a synthetic, covalently linked mimic of the extracellular matrix (ECM). The HA and gelatin were chemically modified using 3,3'-dithiobis(propionic hydrazide) (DTP). After reduction with dithiothreitol (DTT), the thiol derivatives of HA (HA-DTPH) and gelatin (gelatin-DTPH) were obtained and characterized. To minimize interference with biological function, the degree of substitution of HA-DTPH and gelatin-DTPH was kept below 50%. Solutions of HA-DTPH and gelatin-DTPH in varying blends (20%, 40%, 60%, 80% gelatin) were prepared in 1% w/v NaCl and crosslinked by disulfide bond formation in air. Hydrogel films were dried and further crosslinked with dilute hydrogen peroxide. Disulfide crosslinked HA-DTPH, gelatin-DTPH, and blends thereof, were degradable enzymatically by collagenase and by hyaluronidase (HAse). The rapid digestion of the crosslinked 100% gelatin-DTPH film by collagenase was significantly retarded by the presence of 20% or 40% HA-DTPH. Addition of at least 40% w/v gelatin into the 100% HA-DTPH films significantly improved the attachment and spreading of Balb/c 3T3 murine fibroblasts seeded on the surface of the hydrogel. These results demonstrate that disulfide-crosslinked HA-gelatin hydrogels, a new type of covalent synthetic ECM, constitute biocompatible and biodegradable substrata for cell culture in vitro.