Anionic poly (lactic acid)-polyurethane micelles as potential biodegradable drug delivery carriers

Amphiphilic poly (lactic acid, PLA)-polyurethane (PULA) containing carboxylic groups was synthesized via step polycondensation. Anionic PULA micelles were prepared by microphase separation process and the critical micelle concentration (CMC) was calculated by determining the solubilizing power to naphthalene in PULA aqueous solution through UV-visible spectrophotometer. By choosing gliclazide as a testing drug, the degradation properties of drug-loaded micelles were investigated by spectrofluorometer method. The results showed that the CMC value was far below that of low molecular weight surfactants. Compared with the blank micelles, the average particle size of micelles with drug entrapped increased and its distribution became narrower. The degradation of PULA micelles could be controlled by adjusting pH value in micellar system. The carboxylic groups in the micelles had great influences on the drug-releasing rate, which was much lower than that of micelles derived from PEG–PLA block copolymer.