If you chose covalent cross-linking of amine containing polymer then I suggest to use dextran polyaldehyde, which does not have such drawback as glutaraldehyde, due to high molecular weight. Please have a look the ref. Oxidized gextran and gelatin. Article Preparation and physicochemical characteristics of cryogel b...
Poly (ethylene glycol) diglycidyl ether is a good crosslinking agent. There are different molecular weight ranges available. PEG units should be highly biocompatible and elastic.