Solubilization And Sustained Release Of Cyclodextrin And Its Derivatives Pesticide Carriers

Neonicotinoids such as thiamethoxam(THX)and imidacloprid are highly efficient,have a broad spectrum of insecticides and are less toxic to mammals.Their share of the pesticide market is getting heavier and heavier.However,it has problems such as short efficacy time,poor water solubility and low utilization rate,which limits its application to some extent.The results show that cyclodextrin and its derivatives embedding pesticides can improve the physical and chemical properties of pesticides,improve the bioavailability of pesticides and reduce environmental pollution.In this paper,the interaction of hydrophilic cyclodextrin(?-CD,HP-?-CD,?-CDP)with THX was studied;interaction of hydrophobic cyclodextrin(TA-?-CD)with THX and interaction of CTS and ?-CD complex with THX.The research contents are as follows:(1)The molar ratio of THX to ?-CD,HP-?-CD and TA-?-CD was determined by phase solubility method and molar ratio method.The results showed that four kinds of CDs and THX formed a molar ratio of 1:1 inclusion complex.Hydrophilic cyclodextrin increases the solubility of THX,wherein the ?-CD solubilization effect is preferably 2.09 times.The results of dissolution test showed that the hydrophilic cyclodextrin inclusion compound promoted the release of the drug,and the hydrophobic cyclodextrin inclusion compound had a sustained release effect.Encapsulation efficiency and drug loading of the spray drying process,and freeze-drying process optimization as the main index.The optimal conditions for the spray drying process are the inclusion compound concentration of 15 mmol/L,the injection flow rate of 10 mL/min,and the injection temperature of 200°C.The optimum process freezedrying inclusion compound was stirred for 6 h,600 r/min,and the heating temperature was 30°C.(2)A three-dimensional network structure of ?-CDP was prepared by using epichloro hydrin as a crosslinking agent.The degree of substitution of epichlorohydrin was calculated to be 10.37 by the phenol sulfuric acid method,and the solubility of ?-CD was 450 mg/mL.The molar ratio of THX to ?-CDP was less than 15 mmol/L by a phase solubility method and the molar ratio was 1:1.The inclusion compound of THX and ?-CD was prepared by spray drying and freeze-drying method,and the drug loading was about 10%.The dissolution test showed that the ?-CDP/THX inclusion complex reached the release equilibrium in about 10 hours,which was about 1.7 times of the release time of the ?-CD/THX inclusion complex.(3)Chitosan(CTS)and ?-CD complexes were used as carriers,and the inclus io n complexes of THX with CTS and ?-CD complexes were prepared by spray drying.The effects of CTS and sodium tripolyphosphate(TPP)mass ratio,different pH and ?-CD/THX concentration on the encapsulation efficiency and drug loading of the inclusion complex were investigated.The results showed that the optimum for the CTS to TPP mass ratio of 5:1,pH 4.5,and CD/THX and CTS mass ratio of 5:1.The results show that the dissolution,CTS,and ?-CD inclusion complex prepared in complex reached equilibrium released in about 24 h,about 4 times ?-CD/THX inclusion compound release time.It is found from the experimental results that ?-CD and HP-?-CD entrap insoluble drugs,which can increase the solubility and promote the rapid release of drugs;TA-?-CD encapsulates poorly soluble drugs,which can achieve sustained release effect;?-CDP is excel ent in water solubility and is a good carrier for controlled release;CTS also has a significant sustained release effect by encapsulating ?-CD/THX by forming a core-shell structure with TPP.