Preparation and characteristics analysis of microspheres of chlorpyrifos and polylactic acid

The sustained-release microspheres of chlorpyrifos was prepared by solvent evaporation method using biodegradable polylactic acid (PLA) as wall materials and chlorpyrifos as core materials.The effects of ratio between core materials to wall materials (chlorpyrifos weight/PLA weight,CP value) and the concentration of PLA on the characteristics of microsphere were investigated.The results indicated that particle diameter,drug-loading rate and entrapment efficiency of microsphere increased with the increase of the concentration of PLA.The particle diameter and drug-loading rate of microsphere decreased when the CP value was decreased from 1∶2 to 1∶5.When the CP value were 1∶3 and 1∶4,the entrapment efficiency of microsphere were 89.88%±1.67% and 90.55%±1.86%,respectively.The smooth and intact microspheres of chlorpyrifos were formed when the CP value were lower than 1∶2.The differential scanning calorimetry (DSC) determination demonstrated that chlorpyrifos and PLA were combined well to form the microspheres.The results indicated that the appropriate concentration of PLA and CP value contributes to the property of the chlorpyrifos microspheres.