Preparation and Properties of Drug Loaded Modified Polylactic Acid Microspheres

The PLA grafted NVP copolymer microspheres were prepared by solvent evaporation extraction method using nimodipine as the model drug and polylactic acid(PLA) as the carrier material.Such main factors as the PLA mass fraction,the emulsifier mass fraction,stirring speed and dosing ratio were analyzed with an orthogonal design.The surface morphology of the microspheres was scanned under electron microscope and the formulation of microspheres was confirmed by FTIR and DSC.The characteristics of the powder particle,such as mean diameter,drug loading rate and entrapment rate,were evaluated comprehensively,and its in vitro release properties were studied.The results show that,with the preparation conditions of 4% PLA mass fraction,3% emulsifier mass fraction,9 000 r/min stirring speed and 2/3 dosing ratio,the copolymer microspheres were round,the surface was smooth,and the average particle size was less than 10 μm with narrow particle size distribution.The microspheres could sustain a continuous release of more than 14 days,and the release rate increased with the increasing graft ratio.