Mechanism analysis of poly-lactic acid microspheres formation by dissipative particle dynamics simulation and experimental study
The dissipative particle dynamics(DPD) simulation method and experimental study were used to investigate the mechanism of poly-lactic acid(PLA) microspheres formation.Nifedipine was used as the model drug,PLA as the carrier,and poly vinyl alcohol(PVA) as the stabilizer,respectively.The mechanism of PLA microspheres formation was developed.The forming process of PLA microspheres consisted of four steps:(1) high dispersion,(2) aggregation of PLA molecules,(3) nifedipine molecules dispersion into the PLA matrix,(4) formation and stabilization of PLA microspheres,sequentially.Based on the mechanism analysis,it was pointed out that there was a maximum of the nifedipine content that the PLA matrix could carry.If the content of nifedipine was below the maximum,almost all the nifedipine molecules dispersed into the PLA matrix.However,when the nifedipine content exceeded the maximum,some nifedipine molecules would be repulsed outside the microspheres,resulting in surplus nifedipine molecules aggregation.