A sponge consisting of a sponge material, such as a polyvinyl alcohol sponge material having a coating of a non adherent mucopolysaccharide, hyaluronic acid ester. The ester can be applied to surfaces of the sponge or can be a uniformly dispersed interstitial gel of an esterified mucopolysaccharide, such as hyaluronic acid, formed by cross linking polyvinyl alcohol with various organic compounds containing carbonyl groups in the presence of acid catalysts, and reacting unreacted portions of the polyvinyl alcohol with the mucopolysaccharide to esterify the mucopolysaccharide and copolymerize the ester with the polyvinyl alcohol.