Water insoluble derivatives of polyanionic polysaccharides

A method for making a water insoluble biocompatible composition, said method comprising combining, in an aqueous mixture, one or more polyanionic polysaccharides, a nucleophile, and an activating agent under conditions sufficient to form said composition, wherein the reaction is carried out at a pH of 3.5 to 8.0 using at least 0.1 molar equivalent of said activating agent per molar equivalent of said polyanionic polysaccharide and at least 1 molar equivalent of said nucleophile per molar equivalent of said polyanionic polysaccharide, and said activating agent is chosen from the group consisting of benzotriazole-1-yloxytris(dimethylamino) phosphonium hexafluorophosphate, O-benzatriazole-1-yl-N,N,N,N′-tetramethyluroniumhexafluorophosphate, bromotris(dimethylamino) phosphonium hexafluorophosphate, bromotris(purrolidinyl) phosphonium hexafluorophosphate, and the corresponding halide salts thereof.