Releasebehaviorandbioactivityevaluationofpyraclostrobin/silicamicrospheres

In order to evaluate the silica drug-loading system, the pyraclostrobin/silica microsphere was prepared by the hydrolysis and polycondensation of tetraethyl orthosilicate under alkaline conditions with pyraclostrobin as the pattern pesticide. The surface morphology and the chemical structure of the microsphere were characterized by scanning electron microscope (SEM), Nicolet iS5 Fourier transform infrared spectrometer (FTIR) and high performance liquid chromatography (HPLC). And its photodegradation rate in water was also determined．The release behavior under different pH/temperature was studied by dialysis bag method. And the growth rate method was employed to study the virulence against Pyricularia oryzae. The results showed that the pyraclostrobin/silica microsphere exhibited regular appearance with the maximum drug loading of 50.73% and the average particle size of 0.998-1.428 μm. Release property was tested under different pH. The results indicated that the release rate of microspheres under alkaline conditions was greater than that of acidic conditions. In addition, the release rates under both acidic and basic conditions were consistent with the first order kinetics equation. And the release in accordance with the Ritger-Peppas equation in the neutral condition. Compared with pH, temperature had little effect on the release rate. The effect of pyraclostrobin/silica microspheres on the fifth day after administration was similar to that of the technical concentrate, while the virulence on the ninth day after administration was 11.7 times higher than that of the technical concentrate, which indicated that the sustained-release effect of pyraclostrobin/silica microspheres was significant. The photodegradation rate of microsphere was 38.98% after 10 hours exposure to ultraviolet light, which is lower than the technical concentrate (68.92%).