| The pesticide slow-release formulation has the advantages of protecting technical pesticide,improving the utilization rate of pesticide,prolonging the effect period,reducing pesticide residue,and protecting ecological environment.Mesoporous Silica Nanoparticle(MSNs)has a large specific surface area,controlled easily particle size,uniform pores,modified easily inner and outer surfaces and excellent biocompatibility,it is becoming a research focus in the field of drug sustained release.At present,the preparation process of MSNs is complicated,the preparation cost is high,and its application in the pesticide field is relatively less.In this study,the existing preparation method of MSNs was simplified,avermectin was used as a model drug,the process parameters were investigated by single factor experiment,and the physical and chemical properties and release characteristics of the prepared avermectin MSNs were characterized,including morphology appearance observation,particle size measurement,infrared spectrum analysis and thermogravimetric analysis,etc.,finally three kinds of preparation method and optimal formula of avermectin-loaded MSNs were obtained,and protective effect to avermectin by the MSNs in the natural environment,as well as the indoor biological activity of the avermectin MSNs on Plutella xylostella was further tested.This study has reference significance for the preparation of drug-loaded MSNs,which is beneficial to promote the application of MSNs in the field of pesticides,and also provides a new way to improve the utilization rate of pesticides and solve the environmental problems of pesticides.The results obtained in this paper are as follows:1.Using tetraethyl orthosilicate(TEOS)as silicon source and cetyltrimethyl ammonium bromide(CTAB)as template to react in an aqueous alkaline ethanol solution,the avermectin MSNs with a particle size of about 100 nm were prepared by simplifying sol-gel preparation method.The microscopic morphology showed that the particle size distribution was uniform and the roundness was good.Infrared spectroscopy indicated that avermectin was successfully loaded by MSNs,loading rate and encapsulation efficiency were 46.3%and 93.3%,respectively;The release mode of avermectin was dissolution,the release rate was stable,and 94.0%of avermectin could be released from MSNs2.Using TEOS as silicon source,CTAB as template,the avermectin MSNs were prepared by solvent evaporation under alkaline conditions.Thin-walled hollow MSNs with high loading capacity and low preparation cost was obtained.Infrared spectroscopy indicated that most of avermectin was successfully encapsulated.The loading rate and encapsulation efficiency were 44.8%and 96.3%,respectively.The release mode of avermectin was dissolution and diffusion,and 83.8%of avermectin could be released from MSNs.3.Using TEOS as silicon source,CTAB as template,the avermectin MSNs were prepared under alkaline conditions by emulsion polymerization.The microscopic morphology showed that the avermectin MSNs thick-walled and hollow.A part of avermectin was in the pores of the microcapsule wall,a part of avermectin was wrapped in the microcapsules,the loading rate and encapsulation efficiency were 32.3%and 96.8%,respectively.The release mode of avermectin was dissolution and diffusion,97.7%of avermectin could be released from MSNs.4.MSNs have significant protective effect on avermectin.Under natural conditions,unprotected avermectin can be degraded by 52.4%,while avermectin in microcapsules prepared by three methods degraded only 13.1%,24.0%and 16.9%.Plutella xylostella was used as control object,and avermectin emulsion oil in water was used as control for biological activity test.The results showed that three avermectin MSNs had a longer duration than emulsion oil in water.The mortality of Plutella xylostella remained above 60%after 15 days of application. |
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