The effects of mPEG proportion and LA/GA ratio on degradation and drug release behaviors of PLGA-mPEG microparticles

The purpose of this research was to evaluate the effects of mPEG proportion and LA/GA ratio on degradation and release behavior of PLGA-mPEG microparticles prepared by the emulsion evaporation method. Mometasone furoate was employed as model drug and encapsulated into five types of PLGA-mPEG microparticles in the same molecular weight (Mw), but different in mPEG proportion or LA/GA ratio. All types of PLGA-mPEG microparticles showed similar drug encapsulation efficiency and particle mean size, but PLGA-mPEG microparticles with higher mPEG proportion showed a faster Mw reduction rate, mass loss rate and size decrease rate according to the in vitro degradation experiment, and also, a faster drug release rate according to the in vitro release experiment. On the other hand, higher LA/GA ratio in PLGA chain of PLGA-mPEG causes a slower Mw reduction rate, mass loss rate, size decrease rate, and thus, a slower drug release rate.