DRUG RELEASE FROM TRIBLOCK COPOLYMERS OF POLY(HYDROXYALKYL L-GLUTAMINE)-POLY(ETHYLENE OXIDE)-POLY(HYDROXYALKYL L-GLUTAMINE)

The loading and release behavior of drugs with various aqueous solubilities from potentially biodegradable block copolymer discs were investigated. The block copolymers used were crosslinked poly(hydroxyalkyl L-glutamine)(PHAG)/poly(ethylene oxide)(PEO)/PHAG block copolymers, which were obtained by aminoalcoholysis of poly(gamma-benzyl L-glutamate) (PBLG)/PEO/PBLG using various aminoalcohols. The release pattern and rate were influenced by the ratio of the two domains, microstructure morphology, drug solubility, and chemical composition which was determined by alkyl length and degree of aminoalcoholysis. In particular, a combination with low PEO content, low drug solubility, low degree of aminoalcoholysis, and longer alkyl chains led to long term constant release from these matrices. This constant release can be explained by a barrier effect of the continuous PHAG phase.