Abstract: Provided is a biomaterial comprising an interpenetrating polymer network (IPN), wherein one of the polymer components is an acidic polysaccharide or a semi-synthetic derivative thereof. The polysaccharide can be hyaluronic acid, and the second polymer component can be a non-toxic, non-carcinogenic synthetic chemical polymer. The derivative can be a total or partial hyaluronic acid ester or a hyaluronic acid salt. The ester or salt can be formed with a pharmacologically active molecule. Methods for preparing the IPN are also disclosed. The acidic polysaccharide or derivative thereof and the synthetic chemical polymer comprising the IPN can be cross-linked, or the synthetic chemical polymer can be grafted onto the acidic polysaccharide. The cross-linking or grafting can be achieved using compounds capable of generating radicals, or via functional groups on the acidic polysaccharide and the synthetic chemical polymer. The IPN can be formed prior to cross-linking or grafting.