Preparation And Study Of Suspension Concentrate Of Microspheres Of Emamection-benzoate

Based on biodegradable poly lactic acid (PLA) as wall materials and Emamectin benzoate as core materials, the sustained-release microspheres of Emamectin benzoate was studied by using solvent evaporation method. The effects of O/W ratio,the temperature of reaction, ratio between core materials and wall materials (chlorpyrifos weight/PLA weight, CP value) and concentration of PLA on the characteristics of microsphere and so on were investigated. Furthermore, the microspheres were tested by the differential scanning calorimetry (DSC) and the drug release properties were investigated. The result showed that the optimistic quality could be achieved while the methylene chloride as the organic solvent, emulsification speed for4000r/min, emulsifier for2.0%of the Arabic gum, Oil-water phase for1:20. When emulsification speed increase gradually,the mean diameter decline at the lowest16.15μm when the emulsification speed is4000rpm;As the concentration of emulsifier of Arabic gum increasing,the mean diameter of microspheres decreased;when the concentration ia at2.0%,the mean diameter is15.13μm.when Oil-water phase increased gradually,the mean diameter decreased at the lowest of10.16μm at1:20.When the temperature of reaction increased gradually,the mean diameter increased,the main reason wa because the volatile speed of methylene chloride was speed up, the clustering phenomenon of microspheres aggravated,leading to the mean diameter increasing. When the temperature of reaction was at20℃,the drug-loading rate was at the highest of19.23%±0.42%,at the same time the entrapment rate was at97.5%±2.03%of the highest.When concentration of wall materials increased.the mean diameter increased.When concentration of wall materials was at150mg/ml,the drug-loading rate and entrapment rate were17.17%±0.73%and85.85%±3.65%of the highest. When the ratio of core material to wall materials increased,the mean diameter of microspheres changing irregularly.When core material to wall materials was at1:2,the drug-loading rate of the Emamectin benzoate microsphere was at the highest of18.65%±0.49%and when the core material to wall materials was at1:4,the entrapment rate was at99%.13±7.33%of the highest. The differential scanning calorimetry (DSC) determination indicated that Emamectin benzoate and PLA were combined well in the microspheres of Emamectin benzoate. The result of drug release properties of Emamectin benzoate/PLA microspheres indicated that the significant sustained-release ability were possessed by microspheres prepared.The Emamectin benzoate/PLA microspheres were prepared with the better technological parameter. Besides, the effect of wetting dispersants, thickening agent, and the anti-freeze agent to microspheres SC was investigated. The results showed that the best quality of the Emamectin benzoate/PLA microspheres SC was produced with proportion of wetting dispersants (A and B)3.0%and3.0%, the thickening agent(Magnesium silicate aluminum)2.5%and anti-freeze agent(glycol)4%, respectively.The toxicity of Emamectin benzoate/PLA microspheres SC to the larva of Plutella xylostella was evaluated. The3%Emamectin benzoate EC was used to evaluate comparative toxicity. The result showed that LC50(0.103mg/L) of the Emamectin benzoate/PLA microspheres SC was higher than LC50(0.072mg/L) of Emamectin benzoate EC which was probably caused by the incomplete release of Emamectin benzoate/PLA microspheres.