聚合物控释微球：药物分散状态对降解和释药的影响

Biodegradable polymeric microsphere shows promise in controlled release and targeted drug delivery. Drug dispersion state is considered to impact on the drug release. In the present work, naltrexone (NTX)-load poly (lactic-co-glycolic acid) (PLGA) microsphere was prepared by O/W emulsification solvent evaporation method and the effects of NTX dispersion state on polymer degradation, microsphere erosion and drug release were investigated. NTX was dispersed in PLGA matrix as solid solution with low drug-loading. In this case, the degradation rate of PLGA and drug release (denoted by release percent) was slightly increased with the rise of drug-loading, but their kinetic characteristics were almost the same. With much higher drug-loading, crystal of NTX was significant formed in the microsphere and the kinetic characteristics of polymer degradation as well as the drug release was transformed significantly. The initial degradation of PLGA became very fast and the porosity of the microsphere became higher. These effects, combined with the fast liberation of crystal drug, resulted in the higher release rate in the initial stage and lower release rate afterwards. In conclusion, the polymer degradation and drug release could be modulated by transforming the drug dispersion state.