Effect of molecular weight and degree of chitosan deacetylation on the preparation and characteristics of chitosan thermosensitive hydrogel as a delivery system

A thermosensitive hydrogel has been prepared with chitosan and alpha beta-glycerophosphate (alpha beta-GP) which could be transited from solution into gel at 37 degrees C. The thermosensitive characteristics, appearance and structure of the hydrogel were affected by concentration, molecular weight and degree of deacetylation (DD) of chitosan. Chitosan, MW 1360 kDa, DD 75.4%, solution concentration 2%) was optimal for preparation of chitosan-alpha beta-glycerophosphate (CS-alpha beta-GP) thermosensitive hydrogel. The appearance of the hydrogel became more compact and regular with increasing concentration and chitosan MW. Model drugs release from CS-alpha beta-GP hydrogel prepared by the drug being added into chitosan solution (method I) was slower than that from hydrogel prepared by the drug being directly added into chitosan hydrogel (method II). The release rate for both adriamycin and 6-mercaptopurine from CS-alpha beta-GP hydrogel decreased with the increase of MW of the chitosan. The hydrophilic model adriamycin was released 60-70% over 24 h which was slower than that of the hydrophobic model 6-mercaptopurine. Therefore it was projected that the CS-alpha beta-GP hydrogel should be an ideal sustained release system especially for hydrophilic drugs. (C) 2007 Elsevier Ltd. All rights reserved.