The study of gelation kinetics and chain-relaxation properties of glutaraldehyde-crosslinked chitosan gel and their effects on microspheres preparation and drug release

The effects of gelation kinetics and chain-relaxation properties of glutaraldehyde-crosslinked chitosan gel on microspheres preparation or drug release were studied. The rate of gelation is zero order corresponding to the chitosan concentration but non-zero order corresponding to the glutaraldehyde concentration. It was suggested that the crosslinking reaction was mainly dominated by the concentration of small molecule reactant, glutaraldehyde. The relaxation of an entangled polymer chain in a gel network as a result of the swelling of cross-linked chitosan hydrogel was investigated by the stress¯strain determination. The higher the cross-linking density of chitosan hydrogel, the lower the swelling ability of chitosan hydrogel due to the slower relaxation rate of polymer chain, which then results in the decreased drug-release rate.