Controlled release of water-soluble macromolecules from bioerodible hydrogels

A bioerodible hydrogel based on water-soluble unsaturated polyesters crosslinked through the double bonds and capable of immobilizing water-soluble macromolecules has been developed. As the ester linkages cleave, the entrapped macromolecule is gradually released to the surrounding aqueous environment. In vitro rate of hydrolysis and concommitant macromolecule release can be controlled by constructing unsaturated polyesters containing varying proportions of esters activated by electron-withdrawing substituents vicinal to the ester function and/or by varying crosslink density. Polyesters containing unsaturation either in the polymer backbone or pendant have been prepared. Macromolecule-containing hydrogels have been fabricated as dessicated microspheres that can be resuspended in water and passed through a 22-gauge hypodermic needle.