A novel synthetic route for the preparation of hydrolytically degradable synthetic hydrogels

A variety of approaches have been described for the modification of synthetic, water soluble polymers with hydrolytically degradable bonds and terminal vinyl groups that can be crosslinked in situ by photo- or redox-initiated free radical polymerization. However, changes in macromer concentration, functionality, and molecular weight commonly used to achieve variable degradation rates simultaneously alter hydrogel mechanical properties. Herein, we describe a novel, two-step synthetic route for the preparation of hydrolytically degradable, crosslinkable PEG-based macromers based on chemical intermediaries that form ester linkages with variable alkyl chain length. Changes in the concentration of a single macromer were shown to provide effective variation of degradation, but with corresponding significant changes in tensile properties. Through variation in the alkyl chain length of the chemical intermediary, variable degradation times ranging from weeks to months are achieved, without significantly affecting initial gelation efficiency, swelling, or tensile properties. When modified with adhesive ligands hydrogels supported viability of encapsulated and adherent cells. Controlled release of a model protein (Immunoglobulin G) was attained as a function of hydrogel degradation rate. Independent control of hydrogel degradation and mechanical properties will offer improved flexibility for studying the effect of these material characteristics on cellular function and may be useful in the design of matrices for tissue engineering and controlled release of bioactive molecules. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 90A: 1073-1082, 2009