Controlling Degradation of Hydrogels via the Size of Crosslinked Junctions

Hydrogels are being increasingly called upon to perform complex functions in biological applications[1] Their assistance in fulfilling these roles is frequently hypothesized to depend upon their playing a temporarily dynamic role via controlled degradation.[2] A variety of hydrogel systems prepared with degradable polymers have been previously developed (e.g., poly(lactide) and its derivatives,[3,4] hyaluronic acid[5] gelatin[6] or polymers modified to be labile to hydrolysis,[7] gels crosslinked with enzymatically labile molecules[8]), in which the degradation rate is mainly regulated by various intrinsic and extrinsic chemical factors. However, controlling material degradation via a simple physical dissociation of polymer molecules may provide advantages over chemical degradation. In this report, we introduce a new approach to regulate the degradation kinetics of ionically crosslinked gels via controlling the dissociation rate of the polymer chains. We also demonstrate the importance of controlling the degradation of these hydrogels to the formation of cartilage tissues that result from cell transplantation.