Construction,Characterization And Pharmacodynamic Evaluation Of Nano-delivery Systems Of Three Poorly Water Soluble Pesticides

In conventional agroecological systems,pesticides are primarily used to control pests,diseases and weeds in order to ameliorate the yield and quality of crop products.However,most of pesticide compounds are generally poorly soluble in water which is not beneficial to maintain bioactivity and increase efficacy and safety of the active ingredients after spraying.The conventional pesticide formulations generally involve emulsifiable concentrate?EC?,suspension concentrate?SC?,wettable powder?WP?and water dispersible granule?WDG?,et al..These formulations have several disadvantages,such as poor dispersion in water,dust drift in atmosphere and organic solvent pollution in ecosystem,consequently,decreasing the control efficacy and increasing the environmental risk of pesticide.This study focuses on three typical large tonnage insoluble pesticides,emamectin benzoate,beta cypermethrin and lambda-cyhalothrin,taken drug particle size,Zeta potential,morphology,storage stability,leaf contact angle,leaf retention and biological activity as evaluation indices of nano delivery systems,the main research results are as follows:1.The solid nanodispersion of?15.0%??w/w?benzoate benzoate was prepared by solidifying nanoemulsion method.The average particle size and Zeta potential of the redispersed dispersion were96.6±1.7 nm and 31.3±0.5 mV,respectively.The leaf contact angle of solid nanodispersion in the hydrophobic surface of cabbage was 98°,the hydrophilicity surface of cucumber was 49°,the wettability,spreadability and permeability was better than that of the control formulation of microemulsion and water dispersible granules,which was conducive to enhance its adhesion and distribution in the leaf.The leaf retention of solid nanodispersion on hydrophobic rice surface were 0.89,1.00,3.17,3.12,3.32 and 4.77 times of contrast commodity pesticide ME-A,ME-B,WDG-A,WDG-B,WDG-C and deionized water,respectively.The leaf retention of solid nanodispersion on hydrophobic cabbage leaves were 1.11,1.12,1.27,1.31,1.33,and 1.76 times,respectively,of contrast commodity pesticide ME-A,ME-B,WDG-A,WDG-B,WDG-C and deionized water.The leaf retention on the hydrophilic cucumber leaves were 1.04,1.05,1.04,1.00,1.05 and 1.04 times of contrast commodity pesticide ME-A,ME-B,WDG-A,WDG-B,WDG-C and deionized water,respectively.The bioassay median lethal concentration(LC₅₀)of contrast commodity pesticide ME-B,WDG-A,WDG-B,WDG-C were 1.24,1.45,1.81 and 1.87 times of solid nanodispersion against the diamondback moth,which showed that the solid nanodispersion had the strongest sensitivity against diamondback moth.The bioassay median lethal concentration(LC₅₀)of contrast commodity pesticide WDG-A and WDG-B were 2.14 and 2.65 times of solid nanodispersion against the myzus persicae,which showed that the solid nanodispersion had the highest toxicity against myzus persicae.Nanocrystallization enhanced the biological activity of the pesticides.Compared with the commodity ECs,MEs and WDGs,the components content of emamectin benzoate in solid nanodispersion increased to 15.0%,dosage form composition avoided the useing of organic solvents,and significantly reduceed the amount of surfactant.2.The 4.5%?w/w?microemulsion of beta cypermethrin was preparated by self emulsifying method.The average particle size and Zeta potential of the dispersed aqueous nano emulsion were 9.4±0.1 nm and-10.9±0.6 mV,respectively,with good uniformity and excellent storage stability.The leaf contact angle of microemulsion in the hydrophobic surface rice was 108°,in the hydrophobic surface of cabbage leaf was 91°,in the hydrophilicity surface of cucumber leafwas 55°,less than that of the control dosage form,which showed that the wettability of the microemulsion formulation of beta cypermethrin in the hydrophobic rice and cabbage and hydrophilic cucumber plants leaves surface,was superior to the control of the formulation of microemulsion,the traditional dosage form of water emulsion and suspension agent,has good wetting and penetration.The retention of beta cypermethrin microemulsion in hydrophobic rice leaves were 1.02,1.10,1.49,1.48,1.70,1.67,0.89 and 4.31 times,respectively,of control formulation ME-B,ME-C,EW-A,EW-B,SC-A,SC-B,EC and deionized water;the retention of beta cypermethrin microemulsion in hydrophobic leaf of cabbage were 1.10,1.10,1.22,1.26,1.35,1.35,0.93 and 2.04 times,respectively,of the commercially available agent of ME-B,ME-C,EW-A,EW-B,SC-A,SC-B,EC and deionized water;the retention of beta cypermethrin microemulsion in the hydrophilicity of cucumber leaves were 1.00,1.04,1.08,1.09,1.09,1.08,0.88 and 1.17 times,respectively,of the control forms ME-B ME-C,EW-A,EW-B,SC-A,SC-B,EC and deionized water.The retention of microemulsion in rice and cabbage leaves was higher than that of commercial formulation emulsions in water and suspensions concentrate.The retention of microemulsion in cucumber leaves was no significant difference compared with the control preparation.Bioassay showed that,the lethal concentration(LC₅₀)of SC-A and EW-A against aphis gossypii glover were 1.50 and1.12 times,respectively,of the ME-A.And the microemulsion had the strongest sensitivity against aphis gossypii glover.The virulences of agent SC-A and EW-A against myzus persicae were significantly lower than that of ME-A,the LC₅₀ of agent SC-A and EW-A against myzus persicae were 1.90 and 1.45times of ME-A,respectively.The microemulsion enhanced the biological activity compared with the control commercial formulation emulsions in water and suspensions concentrate.3.The 3.0%?w/w?microemulsion ME-A,ME-B and ME-C of beta cypermethrin·emamectin benzoate two component were prepared by the self emulsifying method.The average particle size of ME-A redispersible nano emulsion and Zeta potential values were 15.7±0.3 and-10.0±1.0 nm mV,respectively.The average particle size of ME-B redispersible nano emulsion particle size and Zeta potential values were 44.6 nm±3.4 and-17.7±1.5 mV.The average particle size of ME-C average particle size of nano powder and emulsion and the Zeta potential values were 16.7±0.2 and-14.6±0.5mV nm.The leaf contact angle of microemulsion ME-A of beta cypermethrin·emamectin benzoate on the rice surface was 92°,on the cabbage leaf surface was 79°,on the cucumber leaf surface was 50°;The leaf contact angle of microemulsion ME-B on rice leaf surface was 94°,on the cabbage leaf surface was 83°,on the cucumber leaf surface was 53°;The leaf contact angle of microemulsion ME-C on rice leaf surface was 97°,on the cabbage leaf surface was 87°,on the cucumber leaf surface was 55°;less than the control commercial dosage forms ME-D,ME-E and ME-F,showed that the ME-A,ME-B and ME-C had the better wettability,permeability and wettability on the hydrophobic and hydrophilic plant leaves surface.The retention of microemulsion ME-A,ME-B and ME-C in rice,cabbage and cucumber leaves were higher than the commodity.Bioassay results showed that,the median lethal concentration(LC₅₀)of control ME-D,ME-E,ME-F against aphis gossypii glover were 1.36,1.29 and 1.86 times of ME-A,respectively;the median lethal concentration(LC₅₀)of control ME-D,ME-E,ME-F against aphis gossypii glover were 1.22,1.16 and 1.67 times of ME-B,respectively;the median lethal concentration(LC₅₀)of control ME-D,ME-E,ME-F against aphis gossypii glover were 1.13,1.08 and1.55 times of ME-C,respectively.The median lethal concentration(LC₅₀)of control ME-D,ME-E,ME-F against myzus persicae were 1.21,1.64 and 1.90 times of ME-A,respectively;the median lethal concentration(LC₅₀)of control ME-D,ME-E,ME-F against myzus persicae were 1.07,1.45 and 1.69times of ME-B,respectively;the median lethal concentration(LC₅₀)of control ME-D,ME-E,ME-F against myzus persicae were 1.10,1.49 and 1.73 times of ME-C,respectively.The results showed that,the biological control effect was gradually increased with the reduce of the size of the nanoparticles,compared with the traditional pesticide formulation,the biological activity was increased.Compared with the commercial formulation,the prepared microemulsion used only a small amount of organic solvent and surfactant.4.The solid nanodispersion of?27.0%??w/w?lambda-cyhalothrin was prepared by the melt emulsifing-carrier curing method.There was no organic solvent in the preparation and composition,and the assistant was environmental protection.The average particle size of the solid nanoparticle was20.63 nm and the dispersion was good.The leaf surface contact angle of solid nanodispersion on rice was 87°,on cabbage leaf was 78°,are less than the control formulation of EC and microcapsule suspension,which showed that it has better wettability on hydrophobic surface.The leaf retention of solid nanodispersion on the rice leaves surface was 12.03 mg/cm²,and on the cabbage leaves was about16.94 mg/cm²,which was the same as that of the commercial formulation EC,and higher than microcapsule suspension.The field efficacy test further confirmed that the improvement of the physical and chemical properties and the interfacial properties of the preparation were indeed helpful to improve the biological control effect.The control effect of solid nanodispersion on striped rice borer and cabbage caterpillar was good,and quicking and lasting effect had good performance,especially on the striped rice borer,in the premise of ensuring the efficacy,the dose could be reduced up to 56.8%,significantly improved the effective utilization rate of pesticides,reduce the dosage,was a kind of new pesticide formulation with a great advantage.