methods are disclosed for preparing novel biodegradable cross - linked nanoparticles based on covalently cross - linking modifications of hyaluronic acid . the final products of the present invention are stable in aqueous media , and may be used as detergents and as additives for pharmaceutical compositions for drug delivery , dna carrier system and other applications . the nanoparticles made from the biopolymers of the present invention may also be used in controlled release applications , super - absorbent materials as well as biomaterials like enzyme immobilization .