Research On The Preparation And Performance Of Prothioconazole Microcapsules And Biodegradable Antifungal Films

Prothioconazole is a sterol demethylation inhibitor（DMIS）fungicide launched in 2004.It has a good inhalation activity,excellent protection,treatment and eradication performance,and is in a leading position in the global fungicide market.However,it is easy to decompose when exposed to light in an aqueous solution and poses a potential health risk to the pesticide application personnels.Controlled-release formulations of pesticides can effectively solve the problems of fast release of active ingredients,short lasting time,easy photolysis,irritation to humans and animals,and exposure and health risks to the pesticide application personnels.At present,the formulations of prothioconazole at home and abroad are mainly suspension concentrates,emulsifiable concentrates and dispersible oil suspending concentrates,and there are few reports on controlled-release formulations.This article focuses on the development of sustained-release formulations of prothioconazole,and aims to provide a theoretical and application basis for the rational use of prothioconazole.The main research contents are as follows:First,prothioconazole microcapsules were prepared by emulsification solvent evaporation method using biodegradable polyhydroxybutyrates as the carrier materials,and the effect of preparation parameters mainly including core wall material mass ratio,oil-water volume ratio,emulsifier mass fraction,and shearing rate on the performance of the microcapsules was explored through single factor experiments.Spherical microcapsules with a particle size D₅₀ of 3.32μm,a span of 2.82,a drug loading of 15.52%,and an encapsulation efficiency of 80.24%were selected and prepared by the L₉（3⁴）orthogonal test.The microcapsules have good sustained-release performance,and its release kinetics conforms to the Fick diffusion law,showing two processes of initial"burst release"followed by"sustained release".Compared to prothioconazole technical material,the photostability of the microcapsules in aqueous solution is enhanced,and the photolysis half-life is doubled.The mycelial growth inhibition test shows that its inhibitory activity against the pathogen of Sclerotium rolfsii Sacc.is equivalent to that of the technical material.Secondly,the biodegradable polymer material polyhydroxybutyrate（PHB）was blended with the fungicide prothioconazole（PRO）,and PHB/PRO composite films with different drug loadings were prepared by the method of petri dish casting.The surface morphology,formation mechanism,thermodynamic properties,mechanical properties and release properties of the composite films in the buffer medium were characterized and measured by SEM,FTIR,TGA,DSC,HPLC,ultraviolet spectrophotometer and universal testing machine.The results show that the mechanical properties of the PHB films have been significantly improved with the addition of prothioconazole;the light transmittance in the range of 400-1000 nm can reach about 60-80%;and thermodynamic properties show that the thermal decomposition stability of PHB films is improved by the adding of prothioconazole.The composite films have good sustained-release performance,and its release kinetics conforms to the Fick diffusion law,and also presents two processes of"burst release"and then"slow release".Indoor biological activity determination and pot experiment show that the pesticide loading of the composite film is of great significance for controlling the growth of pathogenic bacteria in the soil and the growth of crops themselves.Through comprehensive evaluation and testing of the performance of composite films with different drug loadings,the optimal pesticide loading for industrial applications is 3.75%.Thirdly,polyurethane prothioconazole microcapsules were prepaed by interfacial polymerization.Using the abundant amino groups on the surface of the polyurethane microcapsules,glutaraldehyde is used as a cross-linking agent to carry out a cross-linking reaction with amino-oligosaccharins to prepare polyurethane cross-linked amino-oligosaccharins prothioconazole microcapsules.The particle size of the polyurethane microcapsules is 567.8 nm.After the cross-linking of amino-oligosaccharins,the particle size of the microcapsules increases to 1641.0 nm,and the encapsulation efficiency increases from 77.04%to 86.39%.The release mechanism of the polyurethane microcapsules is mainly non-Fick diffusion.After cross-linking,the release mechanism of amino-oligosaccharins is more complicated,mainly based on the erosion of the capsule wall;the photostability of the microcapsules in aqueous solution is enhanced;The mycelial growth test showed that its inhibitory activity against the pathogen of peanut Sclerotium rolfsii Sacc.is equivalent to that of microemulsion;and the microcapsules after cross-linking of amino-oligosaccharins have higher biological activity against peanut S.rolfsii,and have a certain promotion effect on wheat growth and drought resistance.The difference between the morphology and performance of the microcapsule suspension and the microcapsule powder was compared and characterized.The results showed that the particle size of the microcapsule powder was larger than that of the microcapsule suspension,and the sustained release performance was more excellent.In conclusion,the industrial production and application of microencapsulation and film of prothioconazole using polyhydroxybutyrate or synthetic polyurethane as wall material is of great significance to improve the efficacy,prolong the duration of efficacy,and reduce the use of pesticides and facilitate the sustainable development of the environment.