Preparation And Application Of Rotenone Nanoparticles Based On Two Types Of Mesoporous Silica

Rotenone is an excellent botanical insecticide,which has good insecticidal activity against vegetable pests such as thrips,aphids and Pieris rapae.However,its stability in the environment is poor,and is easily oxidized,photodegraded and hydrolyzed in the environment.The residual time on crops is short,and after rotenone is applied to the plant,only a very small amount of rotenone can be absorbed by the plant,resulting in a greatly reduced utilization efficiency of rotenone.Mesoporous silica nanoparticles(MSNs)are ideal carriers for drug loading due to their considerable specific surface area and pore volume,good biocompatibility,nanoscale size and controllable particle size.In this paper,MSNs and HMSNs were prepared by different preparation methods.The properties of two kinds of nanoparticles,as well as the stability and sustained-release properties of rotenone after drug loading were studied.Cucumber plants and the 3rd instar larvae of Spodoptera litura were used as model plants and insects to study the systemicity and insecticidal activity of two kinds of rotenone nanoparticles.The main results are as follows:(1)MSNs were prepared by triethanolamine alkaline medium synthesis method,and rotenone was loaded into the channels of MSNs by solvent evaporation method to prepare rotenone-loaded MSNs(Rot@MSNs),when the mass ratio of rotenone to MSNs was 1:1,The drug loading rate can reach the maximum value of 31.1%.The MSNs were characterized by transmission electron microscopy(TEM),scanning electron microscopy(SEM),and dynamic light scattering analysis(DLS).The results showed that the particle size of MSNs prepared by this method was about 70 nm,with good dispersion and uniform particle size;The results of nitrogen adsorption and desorption analysis showed that the spqcific surface area was 342.6m2/g,the pore volume was 0.65cm3/g,and the pore size was 2.8 nm.In addition,the data of MSNs decreased significantly after rotenone was loaded,which proved that rotenone existed in MSNs channels;Fourier transform infrared spectroscopy(FTIR)analysis showed that rotenone was successfully loaded and its physicochemical properties did not change.The release behavior of rotenone had the highest fitting degree under the Ritger-Peppas model,which was in line with the Fickian diffusion behavior.(2)Hollow mesoporous silica(HMSNs)was synthesized by self templating method with solid MSNs and water as etchant.Rotenone loaded HMSNs(Rot@HMSNs)were also prepared by solvent evaporation method.After the optimization of drug loading time and drug loading amount,the results showed that when the mass ratio of rotenone to HMSNs was 2:1,the drug-loading rate reaches a maximum of 46.7%.The HMSNs were characterized by TEM,SEM,and DLS.The results showed that the particle size of HMSNs was 250 nm,with uniform particle size and good dispersibility;The results showed that the specific surface area of HMSNs was 999.4 m2/g,the pore volume was 0.62 cm3/g,and the pore diameter was 3.3 nm.After rotenone loading,the data of HMSNs decreased significantly,which proved that rotenone was successfully loaded into the pore and inner cavity of HMSNs;FTIR analysis showed that rotenone was successfully loaded and its physicochemical properties did not change.The release behavior of rotenone was the best fit under the Ritger-Peppas model,which was in line with the release behavior of Fickian diffusion and dissolution of skeleton.(3)The study found that Rot@MSNs and Rot@HMSNs have the same insecticidal activity against Spodoptera litura larvae as ME,and blank MSNs and HMSNs can also have certain effects on Spodoptera litura larvae.To explore whether MSNs and HMSNs could be absorbed by cucumber leaves,FITC was grafted onto MSNs and HMSNs and visualized under confocal laser scanning microscope(CLSM).The distribution of rotenone in cucumber plants was studied by applying rotenone on leaves.The results of the study show that both MSNs and HMSNs can be absorbed by plant leaves and are found in the stems and roots of plants.The upper leaves,treated leaves,lower leaves and roots of cucumbers with Rot@MSNs and Rot@HMSNs were taken and analyzed by high performance liquid chromatography(HPLC).The results showed that MSNs and HMSNs can increase the content of rotenone in cucumber plants,and the ability to conduct downward is stronger.