Ocular and brain biocompatibility of polymeric delivery materials prepared from ester derivatives of hyaluronic acid

We have tested the biocompatibility of a new class of controlled-release polymers derived from hyaluronic acid using two in-vivo models: the rabbit cornea and the rat brain. We compared the tissue reaction in the presence of these materials to that seen with absorbable gelatin sponge (Gelfoam^R) and oxidized regenerated cellulose (Surgicel^R). In the cornea, the polymers produced different inflammatory responses, which generally correlated with their rate of degradation in the tissue. In the brain, similar degrees of inflammation and rates of degradation were observed, with no evidence of adverse neurological reaction or systemic toxicity. We conclude that polymers derived from hyaluronic acid should be explored further as potential vehicles for carrying therapeutic agents into the brain, and that the rabbit cornea and rat brain models could be used as an initial screen for polymer biocompatibility.