Preparation Of Monodisperse Nanocapsules And Their In Vitro Release Behavior

Chemical control of weeds and insect pests by pesticides has great advantages suchas high efficiency, easy to operation, wide practicability and remarkable economicbenefits. In short, pesticide played an inestimable role in ensuring food production.However, there wereserious drawbacks of traditional pesticide formulations resulting inlow utilization rate and short-term validity, and the wasted pesticides not only resultedin serious environmental pollution but also the resources waste. Microcapsule pesticide,as a new pesticide formulation of low toxicity, high efficiency and controlled releaseproperty, has broad applied prospect for its advantages in enhancing the efficacy ofpesticide, protecting environment and ensuring food safety.Electrospray technique is an effective, easy and green way to preparemonodisperse microcapsules with high entrapment ratio under mild conditions.However, it is hard to preparecapsulesin nanoscale withtraditional electrospraytechnique,especiallywhen the carriers areenvironment-friendly and water-soluble natural polymers，which limitedthe application of this technology in the development of newenvironment-friendly pesticide formulations.In order to overcome the shortages of traditional electrospray technique, the effectsof solute and solution properties on particle size were studied, theelectrosprayinstrument was modified, and the feasibility for preparation ofwater-soluble polymernanoparticles with modified instruments was tested byoptimizingprocess parameters. In addition, the process parameters of drug-loadednanocapsules were studied and optimized with acetamiprid as the model drug. The mainresults are as follows:(1) First of all, the diameter of water-soluble polymer microparticles could bereduced greatly via the modified electrospray device.The alginate/chitosanmicroparticles with mean diameter of463.3±83.4nm were successfully preparedwhenthe parameterswere optimized and the solvent as well as solution properties wereadjusted. The nanoparticles were regular sphere in appearance and quasi monodispersein size, and most important, the higher zeta potential (20-30mV) of thenanoparticleswould facilitate the stability of the nanoparticle suspension. The optimumexperimental conditions were: concentration of alginate was1.6w/v%, concentration ofchitosan was0.01w/v%, feeding rate of0.2mL/h, working distance of1.0cm, and voltage of16kV.(2) Acetamiprid-loaded alginate/chitosan nanocapsules with high encapsulationefficiency, loading capacity and good redispersibility were prepared via the modifiedelectrospray device. The mass ratio of acetamiprid/alginate were one of the mainfactors influenced the diameter of the microcapsules, the diameter of nanocapsules was430±79nm and557±89nmwhen the mass ratio of acetamiprid/alginate was1:3and1:1respectively. Meanwhile, pH, CaCl2and chitosan concentration of the coagulantsolution all played a significant role in encapsulation efficiency of the nanocapsules,andthe minimum encapsulation efficiency was up to61.74±3.84%at all experimentconditions.(3) The results of drug releasestudy indicated that factors such as the mass ratio ofacetamiprid/alginate, concentration of chitosan, and diameter of microcapsulesinfluenced on behavior of drug release. Low mass ratio of core/wall and highconcentration of chitosan facilitatedextending release time of the drug. Microcapsuleswith larger size displayed more obvious sustained release behavior for their lowerspecific surface area and thicker diffusion matrix. The drug release behavior fromalginate/chitosan microcapsules obeyed the first-order release kinetics model and thepattern of water-soluble drug releasing from porous matrix,and the release process wascontrolled by diffusion of the drug and degradation of the microcapsules.