Lactic acid oligomer microspheres containing hydrophilic drugs

A new method was developed for preparation of biodegradable lactic acid oligomer microspheres containing hydrophilic drugs. The microspheres were obtained by removal of solvent from an O/O (oil-in-oil) emulsion through evaporation. The solvent used for the dispersed phase solution was an acetonitrile: water mixture, while the continuous phase medium was cottonseed oil. Doxorubicin hydrochloride (ADR) and insulin were successfully entrapped in the microspheres with high trapping efficiencies of 80 to 90%, and their release profiles were not accompanied with the significant burst effect. The release rate of the drugs from the microspheres was greatly affected by the initial loading of the drugs and the molecular weight of the lactic acid oligomer.