pH响应型毒死蜱水凝胶体系的构建及其缓释性能

Construction of pH-responsive chlorpyrifos hydrogels system and its controlled-release property

传统农药易受到环境因子的影响而过早降解,导致利用率低下,利用响应型控释技术对传统农药剂型进行改善是提高农药利用率的有效措施。本研究使用多巴胺改性凹凸棒负载毒死蜱(CPF),将海藻酸盐作为包覆材料,利用外源挤出法与Ca^(2+)交联,制备了能够对碱性条件作出特定响应的多巴胺改性凹凸棒/毒死蜱/海藻酸钙复合水凝胶(PRCH)。通过扫描电镜(SEM)、ζ-电位和比表面积测试(BET)对PRCH的形貌和结构进行表征,并研究PRCH在不同pH环境介质中的缓释性能、溶胀性能以及在紫外光和不同温度下的稳定性。结果表明:PRCH对毒死蜱的负载率高达85%,并能够在碱性条件下吸水溶胀,导致海藻酸钙孔道打开甚至结构坍塌,从而释放出毒死蜱。利用Korsmeyer-Peppas模型方程拟合曲线阐释PRCH的缓释机理为:在pH=5.5的缓冲液中,毒死蜱的释药速率由药物的扩散和水凝胶溶胀共同决定;pH=7.0时农药传输过程由水凝胶裂解的速率主导;而pH=8.5时农药自身的扩散在毒死蜱的释放过程中起主要作用,但水凝胶的裂解加速了毒死蜱的扩散。PRCH比毒死蜱标准品拥有更强的紫外稳定性和温度稳定性。本研究表明,PRCH具备优异的载药性能、pH特定响应和绿色环保等优势,在提高传统农药施用稳定性和防治效果等方面具有良好的应用前景。

Traditional pesticides are susceptible to environmental factors and their early degradation leads to a low utilization rate.It is an effective measure to improve the utilization rate of pesticides by using responsive controlled release technology.In this study,dopamine-modified attapulgite/chlorpyrifos/calcium alginate composite hydrogels(PRCH)with a specific response to alkaline conditions were prepared using dopamine-modified attapulgite loaded with chlorpyrifos(CPF)and alginate was used as coating material by extrinsic extrusion method and crosslinking with Ca^(2+).The morphology and structure of PRCH were characterized by scanning electron microscope(SEM),Zetapotential,and BET specific surface area tests.The sustained-release and swelling properties of PRCH in different pH environments were studied,and the stability of PRCH under UV light and different temperatures were explored.The results showed that the loading rate of PRCH with chlorpyrifos was as high as 85%.PRCH could absorb water and swell under alkaline conditions,resulting in the opening of calcium alginate channels and even structural collapse to release chlorpyrifos.The release mechanism of PRCH was explained by fitting the curve with Korsmeyer-Peppas model equation:The release rate of PRCH in buffer solution with pH 5.5 was determined by both drug diffusion and hydrogel swelling.When the buffer pH is 7.0,the pesticide transport process is dominated by the cleavage rate of hydrogels.At pH 8.5,the diffusion of pesticide itself played a major role in the release of chlorpyrifos,but the fragmentation of the hydrogels accelerated the spread of chlorpyrifos.In addition,we found that PRCH has stronger UV stability and temperature stability than industrial grade chlorpyrifos.Collectively,PRCH has the advantages such as excellent drug loading rate,pH-specific response characteristics and being environmentally friendly.Therefore,the system has great application prospects in improving the stability and efficacy of traditional pesticides.