In Vivo Characterization of Poly(ethylene glycol) Hydrogels with Thio-β Esters

Resorbable hydrogels have numerous potential applications in tissue engineering and drug delivery due to their highly tunable properties and soft tissue-like mechanical properties. The incorporation of esters into the backbone of poly(ethylene glycol) hydrogels has been used to develop libraries of hydrogels with tunable degradation rates. However, these synthetic strategies used to increase degradation rate often result in undesired changes in the hydrogel physical properties such as matrix modulus or swelling. In an effort to decouple degradation rate from other hydrogel properties, we inserted thio-β esters into the poly(ethylene glycol)-diacrylate backbone to introduce labile bonds without changing macromer molecular weight. This allowed the number of hydrolytically labile thio-β esters to be controlled through changing the ratios of this modified macromer to the original macromer without affecting network properties. The retention of hydrogel properties at different macromer ratios was confirmed by measuring gel fraction, swelling ratio, and compressive modulus. The tunable degradation profiles were characterized both in vitro and in vivo. Following confirmation of cytocompatibility after exposure to the hydrogel degradation products, the in vivo host response was evaluated in comparison to medical grade silicone. Collectively, this work demonstrates the utility and tunability of these hydrolytically degradable hydrogels for a wide variety of tissue engineering applications.