Preparation Of Sustained-Release Carriers For Nepeta Essential Oil And Its Repellent Properties

Mosquito is a kind of main sanitary pest,its main harm is to spread virus and disease.In the absence of vaccines against mosquito-borne diseases,the use of mosquito repellent is an effective measure to prevent mosquitoes from biting humans.Traditional chemosynthetic mosquito repellents can achieve good repellent effect at the initial stage of use,but these mosquito repellents have disadvantages such as single mechanism of action,short action time and other problems,which lead to the decline of mosquito repellent effect.In addition,with the increasing number of reports on the potential toxicity of chemically synthesized classes of mosquito repellents,there has aroused widespread concern about the residual toxicity of sanitary pesticides.The application of plant-derived pesticides in the field of mosquito repellent is considered a green and safe alternative strategy.Essential oils is a secondary metabolite of plant and belongs to plant-derived pesticides.Among them,nepeta essential oil has been widely studied for its high repellent activity,which is a potential repellent material.However,the instability of essential oils and poor water solubility of essential oils limit their application in mosquito repellent field.In this study,it is innovative that use coaxial electrospinning technology and the microencapsulation technology of electro-atomization complex coacervation method successfully coated nepeta essential oil.Thus,the utilization rate and mosquito repellent performance of essential oil are significantly improved.It provides a novel technical route for the application of nepeta essential oil of schizonepeta in mosquito repellent field.The main research contents are as follows:1.Preparation and properties of nanofiber containing nepeta essential oil.Polylactic acid was used as the wall material and nepeta essential oil as core material,polylactic acid fiber containing nepeta essential oil was prepared by coaxial electrospinning technology.The suitable concentration of polylactic acid solution and flow rate of nepeta essential oil were determined by single factor test,which were 10 wt% and 4 m L/h,respectively.Under the optimal spinning conditions,the coaxial fibers had good morphology,the average diameter was 0.74μm,and the loading capacity and encapsulation efficiency of coaxial fibers were 20.20% and 84.18%,respectively.The fourier transform infrared spectra and thermogravimetric analysis showed that the nepete essential oil has been successfully loaded in polylactic acid fiber,and its thermal stability has been improved due to polylactic acid encapsulation of essential oil.The results of the release test and the mosquito repellent test showed that the nepeta essential oil could be released for about 45 days and the mosquito avoidance rate could be maintained about 80%within 72 hours by coaxial electrospinning technology.These results indicated that the fiber had good slow-release properties and mosquito repellent properties,and has potential for application in the field of mosquito repellent.2.Preparation and properties of microcapsules containing nepeta essential oil.Sodium alginate and gelatin were used as wall materials and nepeta essential oil as core material,the microcapsules of nepeta essential oil were prepared by electro-atomization complex coacervation method.The effects of sodium alginate solution concentration,core-wall ratio and emulsifier content on microcapsule performance were studied.Compared with other preparation conditions,the microcapsules prepared with sodium alginate solution concentration of 0.15 wt%,core-wall ratio of 2:3 and emulsifier content of 0.075 wt% had higher loading capacity and encapsulation efficiency,which were 13.93% and 86.65%,respectively.The fourier transform infrared spectra and thermogravimetric analysis showed that the nepeta essential oil was successfully encapsulated in the wall material,and at the nepeta essential oil volatilization temperature,the heat leakage phenomenon is effectively prevented.The microcapsules prepared by this method were nearly circular in shape under electron scanning microscope observation,with a particle size range of 22 ～ 43 μm.The results of the release test and mosquito repellent test showed that the nepeta essential oil in the microcapsules could be released stably within 15 days,and the mosquito avoidance rate remained above 80% within 48 h,indicating that the microcapsule has potential application value in the field of mosquito repellent.In conclusion,the mosquito repellent performance of nepeta essential oil has been successfully improved through coaxial electrospinning technology and the microencapsulation technology of electro-atomization complex coacervation method.Due to the characteristics of small size and large specific surface area,the sustained-release carrier can significantly improve the utilization and stability of nepeta essential oil and prolong its validity period,which provides a new idea for the application of essential oil substances in the field of mosquito repellent,and has certain potential for future development.