Study On Microsphere Of Spinosad And Preparation Of Its Suspension Agent

Spinosad was prepared into microspheres using polylactic acid (PLA) as coating materials by emulsion solvent evaporation method first time in pesticide dosage form manufacturing, and the relative optimum prescription and process conditions were obtained, verified this preparing method and studied the stability of Spinosad microspheres preliminarily.5% suspension agent of Spinosad microspheres was prepared, its quality was analysed meanwhile. Compared with 2.5% Spinosad suspension agent saled in the market, bioactivity of 5% suspension agent of Spinosad microspheres against 2nd-instar larvae of Plutella xylostella was investigated. The main contents are as the following aspects:1. The relative optimum prescription and process conditions were determined by investigating the effects of solvents, surfactants and dispersing agents, emulsification conditions, natural light, concentration of emulsifiers, reaction temperature, concentration of PLA and ratio of oil phase volume to water phase volume, etc, on quality of microsphere of Spinosad, which are as followed:0.9g of PLA was dissolved into 10 mL dichloromethane in the condition of ice-water bath, then 0.53 g of Spinosad was mixed into this solution, stirred for dissolving completely.100 mL 12.5mg/mL of gelatin solution was poured into the mixed solution, after being emulsified by high-speed distribution the solution was stirred below the temperature of 35℃and in condition of lucifuge until the odor of dichloromethane could not be smelled. The Spinosad microspheres were obtained after the solid substances were collected and dried. The result shows that D50, span, drug-loading rate, entrapment rate, drug yield of the Spinosad microspheres is 12.73μm,1.4811,31%,100.2% and 89.4% respectively and this preparation process has a good repeatability.2. The shape and surface morphology of Spinosad microspheres were observed by scanning electron microscope (SEM), the result shows that the microspheres are round beads which have relatively smooth surfaces. By comparing the differential scanning calorimetry (DSC) curves of raw Spinosad, PLA, Spinosad microspheres and physical mixtures of Spinosad and PLA, it is found that Spinosad and PLA in microspheres are formed drug-loaded micropheres via chemical bonds indeed. The photochemical stability of Spinosad microspheres was investigated preliminarily, it is found that compared with the solution Spinosad dissolved in methyl alcohol and raw Spinosad, the photochemical stability of Spinosad can be improved by being prepared into microspheres.3. The relative optimum prescription was determined by selecting of wettiing and dispersing agents, thickening agents and antifreeze, etc. The prescription is as followed:the wetting and dispersing agent is a mixture of F2, F5 and F6 whose ratio is 1:1:2 with an total amount of 50 mg/mL; the thickening agent is 30 mg/mL of Magnesium Aluminum Silicate and 50 mg/mL of ethylene glycol is used as antifreeze. After analyzing the quality of this microspheres suspension, the result shows that this suspension matched up to this prescription is up to the standard, whose decomposition rate by heated storage is only around 2%. Laboratory toxicity of 2.5% Spinosad suspension agent saled in the market and 5% suspension agent of Spinosad microspheres against 2nd-instar larvae of Plutella xylostella was investigated. It is shows that the bioactivity figures of the two types of suspension are almost the same.