biodegradable cross - linkers are provided having a polyacid core with at least two acidic groups covalently connected to reactive groups usable to cross - link polymer filaments . between at least one reactive group and an acidic group of the polyacid is a biodegradable region which preferably consists of a hydroxyalkyl acid ester sequence having 1 , 2 , 3 , 4 , 5 or 6 hydroxyalkyl acid ester groups . the polyacid may be attached to a water soluble region that is attached to the biodegradable region having attached reactive groups . the hydroxyalkyl acid ester group is preferably a lactate or glycolate . polyacids include diacids , triacids , tetraacids and pentaacids , and the reactive group may contain a carbon - carbon double bond . a network of cross - linked polymer filaments having adefined biodegradation rate can be formed using the cross - linkers . the network may contain biologically active molecules , and can be in the form of a microparticle or nanoparticle , or hydrogel . the polymer filaments may be preformed polymer filaments of polynucleic acids , polypeptides , proteins or carbohydrates . the cross - linkers may be copolymerized with charged monomers such as acrylic monomers containing charged groups . applications of the cross - linkers and network include controlled release of drugs and cosmetics , tissue engineering , wound healing , hazardous waste remediation , metal chelation , swellable devices for absorbing liquids and prevention of surgical adhesions .