Preparation And Properties Of Drug Loaded Systems For Controlled Release Of Avermectin

Because of the characteristics of low toxicity to human and environment, high performance to pest and high selective, Avermectin was recommended as product replacing the following five high toxicity pesticide : Methamidophos, Parathion, Methyl parathion, Monocrotophos and Ammonium phosphate. However, avermectin is easy to decompose under sunlight ,its residual effect is short in practical application. So improving its stability to sunlight is very important to its development and utilization and prolong its residual effect .This has a big academic realistic significance. Polyethylene glycol andβ-Cyclodextrin(CD) as loading materials respectively by melting method and co-precipetation method were used to prepare the solid dispersion(SD) and nanoparticles of avermectin . And Scanning Electron Microscop(eSEM),Transmission Electron Microscop(eTEM), Infrared Spectroscopy(IR), Ultra Violet spectra(UV)were used to character two drug-loaded systems . On the basis of these , the prepared process was optimized by the orthogonal test , controlled release and UV- shielding properties were studied by in vitro releasing method .The drug-loaded systems were prepared control released formulations , Toxicity and field control effect of control released formulation were studied too. The main conclusion were as follows:1) The solid dispersion was prepared by melting method , and it had a spherical appearance with the diameter 900~1000 nm , the efficiency of encapsulation was 99.36% ,the optimum of preparation conditions for the solid dispersion were established as Avermectin: PEG600010:100, temperature was at 60℃and stirring time was 20 min. 2) IR spectrogram and UV-visible spectrogram indicated the following conclusion:comparing with avermectin TC of avermectin , characteristic peak C=O was disappeared , this can confirmed that avermectin was encapsulated by PEG6000 . Avermectin TC and SD had the same absorption peak at 245 nm , the Value of TC was bigger than SD , this also can confirmed that avermectin was encapsulated by PEG6000 .3) Nanoparticles were prepared by melting method , and it had a spherical appearance with the diameter 50~120 nm .The optimum of preparation conditions for nanoparticles were established as Avermectin:β- CD1:5, the temperature was at 40℃and stirring time was 2 h ,the efficiency of inclusion compound was 65.82% .4) IR spectrogram and UV-visible spectrogram indicated the following conclusion :comparing with TC of avermectin , characteristic peak C=O was abated and Offset slightly , and IR spectrogram of nanoparticles was similar toβ-CD , this can confirmed that avermectin was embraced byβ-CD . TC and nanoparticles had the same absorption peak at 245 nm , the Value of TC was bigger than nanoparticles , this also can confirmed that avermectin was embraced byβ- CD .5) There had a section between the slow released curve of TC and SD , there also had a obvious section between the slow released curve of TC and nanoparticles . The square measure of the former section was smaller than the latter , so these drug-loaded systems had a good controlled release characteristic, and the characteristic of nanoparticles was better . Comparing to TC, the avermectin of SD and nanoparticles were disintegrated slowly under UV-light , and the tendency of these systems was similar ,so the UV- shielding properties of SD and nanoparticles was good and there had no significance difference between SD and nanoparticles .The accumulative release of SD corresponded with zero order kinetics model, and the kinetics equation was ARP=-91.6716e -0.1022 t + 98.1953 , and The accumulative release of nanoparticles corresponded with zero order kinetics model, and the kinetics equation was ARP= -88.4348e -0.1032 t + 86.0599.6) The result of indoor Toxicity Measurement and Field control effect indicated that toxicity of control released formulation to rice planthopper, cnaphalocrocis medinalis and vegetables aphid were higher than the common Chemical formulation , its LC50 were 2.39 mg/kg, 0.89 mg/kg and 0.98 mg/kg. Field control effect of control released formulation to rice pests and vegetables aphid had a faster and longer effect the common Chemical formulation such as Matrine, Avermectin and Imidacloprid.