Research On Preparation, Evaluation And Slow-Release Mechanism Of Three Nano Pesticides

Pesticides are important materials for defending major biological disasters, safeguarding grainproduction and promoting agricultural output steady growth. Pesticide formulations are still based ontraditional dosage forms, in spite they’are rapidly developing in our country, and the effective utilizationof pesticides is generally low. There’re very serious pesticide residues and environmental pollution.People pay close attention to food safety, health risks and ecological environment problems, which arecaused by pesticide pollution. Water-based, dust-free and controlled-release dosage forms become thedevelopment direction of new pesticide formulations.Calcium alginate gel is a kind of natural biological polysaccharide, and has good biocompatibilityand biological adhesion, rich pore structure, strong loading capacity, stable chemical performance, mildpreparation method, wide source and low price. It can prolong the acting time of pesticides release, andprevent sensitive pesticides degradation through stopping pesticides contacting with the surroundingenvironment after they are embedded or inlaid in the pores of calcium alginate gel. Therefore, it canenhance the stability of pesticides. Using advanced nano-materials and nano-technology to produce newnano controlled-release pesticide formulations, which are efficient and safe, is an important way toreduce environment pollution, protect people’s health, and promote sustainable development ofpesticide industry. According to the different physical and chemical properties of pesticides, we firstlyconducted a study on calcium alginate nanocapsules (CANC), abamectin nanosuspension (ANS),controlled-release validamycin nanocapsules (CRVNC) and Zn3P2/calcium alginate nanocapsules(NC-Zn3P2/CA), in order to provide an advanced idea and method to research on new pesticideformulations.The results showed that:(1) CANC are synthesized by W/O reverse microemulsion polymerizationmethod, using sodium alginate and CaCl2as raw materials, cetyltrimethyl ammonium bromide (CTAB)as a surfactant and isopropanol as a cosurfactant. They are good globular, and particle size distributesbetween130nm to480nm, average particle size is252±16nm, particle dispersion index (PDI) is0.222,specific surface area (BET) is260m2·g-1. There’re a large number of pores distributing in the interior ofCANC, and the average pore size is6.2nm. The content of sodium alginate solution, CTAB andisopropyl alcohol has a significant effect on BET of CANC.(2) CRVNC is prepared by embedded through polymerization reaction using sodium alginate andCaCl2as raw materials, and the average particle size is281±18nm, PDI is0.082. Loading effect andcontrolled-release performance are significantly influenced by the addition amount of validamycintechnical and sodium alginate. It has an obvious sudden release phenomenon in water, and there’s avery good inhibitory effect to rhizoctonia solani. Antibacterial rates increase with the increase ofvalidamycin effective concentration. Antibacterial effect of CRVNC on rhizoctonia solani is weakerthan validamycin technical in a relatively short period of time. As prolonging test time, CRVNC startsto reflect superiority of controlled-release, and antibacterial effect of CRVNC on rhizoctonia solani is better than validamycin technical, gradually.(3) NC-Zn3P2/CA is synthesized by inverse microemulsion polymerization method using modernnano processing technology. The particle size distribution is between220nm to580nm, averageparticle size is354±23nm, and PDI is0.195. They are odourless and tasteless, palatability andpharmaceutical efficacy are greatly improved and enhanced, and the ingestion index increased1.2timesto2.3times, killing rate increased4times, compared with Zn3P2technical. There’re obvious suddenrelease phenomenons for NC-Zn3P2/CA. The mass ratio of calcium alginate and Zn3P2(mCA/mZn3P2) hasa significant impact on loading rate and controlled-release performance of NC-Zn3P2/CA. Loadingcapacity of Nano-Zn3P2/CA to Zn3P2reached the saturation point, when the mCA/mZn3P2is1:2.(4) ANS is produced by using sand mill through wet grinding, using methylene naphthalenesulfonate (NNO) as a dispersant, dimethyl polysiloxane as a defoaming agent, poly methoxypolyoxyethylene methyl acrylate as a stabilizer, sodium alginate as a suspension agent. It’s irregularspherical, clear, translucent, evenly dispersed in the water, and the average particle size is586±20nm.There’re some negative charges on the surface, and the surface Zeta potential is-19.5mV. It has a goodsuspension performance and thermal stability. Milling time, and the addition amount of abamectintechnical and NNO have certain impacts on particle size of the ANS.These studies confirmed that using modern nanomanufacturing technology to prepare water-basedpesticide formulations, such as pesticide nanosuspension and controlled-release pesticide nanocapsules,which can raise biological activity and utilization of pesticides, and reduce the usage of various organicsolvent and surfactant. It has a great significance to alleviate environment pollution, maintain ecologicalbalance, and promote the development of green agriculture.