Development And Characterization Of Pesticide Nanoparticles Delivery Systems With Targeted Adhesion

Pesticides are very important to defend against biological disasters and ensure food security.Most conventional pesticide formulations have several disadvantages including excessive use of organic solvent,dust drift and poor dispersity.Meanwhile,the effective utilization rate of pesticide formulations to crop foliage is usually less than 30%,and most of the pesticides?70%-90%?end up in the surrounding environment because of weak adhesion to the targeting crop foliage,leading to the severe pollution of ecological systems and food.Actually,less than 0.1%of an applied pesticides reaches the target pest Therefore,an effective pesticide formulation with high adhesion and retention on crop foliage will be highly desirable to increase the effective utilization rate of pesticides and minimize loss to the environment.To increase the affinty to target crop foliage and prolong retention time of pesticides,we used the nanomaterial and nanotechnology to develop pesticide nano-drug-delivery system?nanopesticides?with strong adhesion to target crop foliage.We have studied the effects of groups on nanopesticides surface on folia affinity in detail,explored the adhesive mechanism of nanopesticides with tannic acid on foliage,and revealed the principle of improved antifugal activity with tannic acid.These experimental results showed that the adhesive modifications on the surface of nanopesticides will be desirable to significantly improve the adhesion and retention of pesticides,and minimize loss to the environment.This study provides a new idea to explore the mechanism of nanopesticides with target affinity modification and controlled release regulation.Our results will be helpful to develop efficient,safe and green pesticide formulations.The contents were listed as follows:?1?Poly?lactic acid??PLA?based nanoparticles with low cost,low toxicity and good biocompatibility are widely used as biodegradable drug carrier.The abamectin could be protected from light irradiation after encapsulation by PLA nanoparticles.We developed three types of functionalized abamectin poly?lactic acid??Abam-PLA?nanoparticles?CH₃CO-PLA-NS,HOOC-PLA-NS,H₂N-PLA-NS?with different adhesion abilities to cucumber foliage.The Abam-PLA nanoparticles were spherical with diameters of around 450 nm,amd the zeta potential values of CH₃CO-PLA-NS,HOOC-PLA-NS and H₂N-PLA-NS were-14.1±0.6,-18.6±0.5,and 9.4±0.2,respectively.We demonstrated the regulatably adhesive mechanism of these nanoparticles on cucumber foliage from macro to micro simply by fluorescence imaging,high performance liquid chromatography?HPLC?analysis and scanning electron microscope?SEM?.H₂N-PLA-NS presented the best adhesion to cucumber foliage by seval modal binding?hydrogen bond,electrostatic attraction and covalent Schiff base?.The retention rate was determined to be 61%by HPLC.Furthermore,the Abam-PLA-NS exhibited better continuous release behavior and photostability compared with active abamectin.?2?The highly adhesive tannic acid modified PLA abamectin nanoparticles?Abam-PLA-Tannin-NS?was formulated by self-assembly mthod.The Abam-PLA-Tannin-NS was spherical with diameters of around 240 nm characterized by SEM.Similar to poly dopamine,tannic acid has a strong adhesion to various surfaces because of incorporating large amounts of catechol groups.Tannic acid was coated on the surface of Abam-PLA to form Abam-PLA-Tannin-NS,and it presented very strong adhesion ability to cucumber foliage by hydrogen bond and potential coordinate bond.The retention rate was determined to be 67%by HPLC.The results of indoor toxicity test showed that the toxicity of Abam-PLA-Tannin-NS has four times better than that of commercial formulations.Furthermore,the Abam-PLA-Tannin-NS exhibited better continuous release behavior and photostability compared with active abamectin.?3?Azox-PLA-Tannin-NS was prepared by nano-drug delivery system process technology mentioned above.The Azox-PLA-Tannin-NS was spherical with diameters of around 250 nm characterized by SEM.The experimental results of contact angle and foliage retention showed that,the nano sized pesticides is beneficial to improve wettability and increase the deposition and adhesion of cucumber foliage.The Azox-PLA-Tannin-NS showed the better indoor toxicity towards fusarium,owing to the antifungal activity from tannic acid itself,and the strong adhesive ability to foliage and fungus.The retention rate was determined to be 59%by HPLC.Furthermore,the Azox-PLA-Tannin-NS exhibited better continuous release behavior compared with active azoxystrobin.