Preparation Of Novel Nano-pesticide Capsules Of Polysaccharide Matrix Polymers And Their Sustained Release Properties

Nanocapsules have important application prospects in the field of new pesticide formulations.The physicochemical properties of nano-pesticide capsules were caused by the wall materials,so the choice of the wall materials was particularly important.In this dissertation,hydrophilic and environment-friendly carboxymethyl chitosan and carboxymethylcellulose sodium were chosed,two polysaccharide matrix polymers were synthesized through hydrophobically modification.Preparation of new nano-pesticide capsules are prepared by containing tebuconazole which was a bacteriostatic agent of carya cathayensis canker disease.The research of interactional mechanism about the new nano-pesticide capsules and protective enzymes of pathogen of carya cathayensis was developed.The antibacterial properties of the new nano-pesticide capsules were studied further at the molecular level.The main research work was as follows:?1?Using carboxymethyl chitosan?CMCS?as raw material,carboxymethyl chitosan derivatives?CMCSD?were synthesised by amidation reaction with tocopherol succinate?Ts?by using catalyst activation method.The FTIR,¹H NMR,X-ray diffraction?XRD?and thermogravimetry?TG?were used to characterize the molecular structure.The tebuconazole nanocapsules were prepared by using ultrasound/swirling method.Dynamic light scattering?DLS?and transmission electron microscopy?TEM?were used to determine the particle size and morphology of the nanocapsules.The encapsulation efficiency,loading rate,and sustained release performance of the nanocapsules were tested by HPLC,and the antibacterial effect was explored by the medium method.The results showed that the successful synthesis of carboxymethyl chitosan derivatives?CMCSD?,micelle critical concentration of 0.1 mg·m L^-1,and successfully prepared the tebuconazole nanocapsules with a particle size of 370.3 nm,the encapsulation efficiency 60.6%,the load rate was 45.7%;compared with tebuconazole suspension,it had good sustained-release performance and antibacterial effects.?2?Carboxymethyl cellulose sodium?CMC?was used as raw material,and carboxymethylcellulose sodium derivatives?CMCD?was synthesised by esterification reaction with tocopherol succinate?Ts?by ionic liquid activation method.The FTIR,¹H NMR,X-ray diffraction?XRD?and thermogravimetry?TG?were used to characterize the molecular structure.The tebuconazole nanocapsules were prepared by sonication/rotary evaporation.Dynamic light scattering?DLS?and transmission electron microscopy?TEM?were used to determine the particle size and morphology of the nanocapsules.The encapsulation efficiency,loading rate,and sustained release performance were measured by HPLC,and the antibacterial effect was explored by the medium method..The results showed that the successful synthesis of sodium carboxymethyl cellulose?CMCD?,the micellar critical concentration of 0.28 mg·m L^-1,and successfully prepared tebuconazole nanocapsules with a particle size of 493.7 nm,the encapsulation efficiency 50.8.%,the load rate was40.4%;compared with tebuconazole suspension,it had good sustained release performance and antibacterial effects.?3?The interaction of Teb?tebuconazole?,CMCSD,CMCD,Teb/CMCSD and Teb/CMCD with a protective enzyme?peroxidase,HRP?was studied by fluorescence emission spectroscopy.The effect of Teb,CMCSD,CMCD,Teb/CMCSD and Teb/CMCD on the conformation of HRP microdomains was investigated by synchronous fluorescence spectroscopy.The results showed that with the increase of Teb,CMCSD,CMCD,Teb/CMCSD,Teb/CMCD concentration or volume ratio,the fluorescence intensity of HRP decreased or increased,indicating that Teb,CMCSD,CMCD,Teb/CMCSD,Teb/CMCD and HRP intermolecular interactions occurred.The binding parameter K of Teb-HRP,CMCSD-HRP,CMCD-HRP,Teb/CMCSD-HRPand Teb/CMCD-HRP systems were 3.548×10³L·mol^-1,1.39×10³ L·mg^-1,1.50×10² L·mg^-1,3.34×10³ L·mg^-1,4.90×10³ L·mg^-1 respectively.Compared with CMCSD-HRP and CMCD-HRP systems,the interaction between Teb/CMCSD,Teb/CMCD and HRP were stronger.The results of synchronous fluorescence spectroscopy showed that with the increase of Teb,CMCSD,CMCD,Teb/CMCSD,Teb/CMCD concentration or volume ratio,the maximum absorption peak wavelengths of tryptophan and tyrosine were blue-shifted or red-shifted,indicating Teb,CMCSD,CMCD,Teb/CMCSD,Teb/CMCD change the conformation of HRP microdomains,the microenvironment of tyrosine and tryptophan were also changed.Combined with emission fluorescence spectroscopy and binding parameter K,it was further verified that Teb/CMCSD,Teb/CMCSD and HRP have strong intermolecular interactions compared with Teb-HRP,CMCSD-HRPand CMCD-HRP systems.And it had a great influence on the conformation of HRP molecules and thus affected the function of HRP.