基于适配体的纳米酶催化调控及其对食品农药残留检测新方法研究

Pesticide residues in food have been the focus of public attention, and the current methodologies are difficult to meet the demands of real-time and on-site detection of pesticide residues. Compared with natural protein enzymes, nanozymes exhibit some distinguished advantages such as the high catalytic stability, large surface area and easy to modification, and have been regarded as an ideal material for sensing signal output, which will make them become an effective tool in the field of analysis. However, nanozymes also have several technical bottlenecks like the low peroxidase activity or poor recognition specificity, and now their detection object is limited to a few targets, which will hinder the further application of them in the detection of pesticide residues and so on. In this project, we will effectively combine aptamers techniques with the catalysis of nanozymes, to develop efficient approaches for regulating the catalytic activity of nanozymes by aptamers or their synergistic effects with other accessory molecules. Meanwhile, aptamers also used as target recognition elements to develop novel methods for the detection of pesticide residues in food, in which the sensing signals will change greatly before and after the addition of pesticides molecules. The regulatory mechanism of aptamers on the catalytic activity of nanozymes will be clarified. We will focus on the construction of high peroxidase catalytic system of nanozymes and their efficient regulatory methods, as well as the determination of sensing conditions for the specific respond to pesticide target molecules, which will provide theoretical and technical support for the further application of nanozymes in the fields of other targets assay or biological imaging.

食品农药残留问题一直是公众关注的焦点，而现有农药检测方法难以满足实时场地检测需求。纳米酶具有催化稳定性高、比表面积大且易修饰等自然酶无可比拟的优势，是传感检测作为信号输出的理想材料，其将成为分析检测领域内的有效工具。然而纳米酶存在过氧化物酶活性相对较低、识别特异性较差等技术瓶颈，目前其检测对象仅局限于少数几个靶标，还未在农药残留等检测方面得到较好应用。本项目将核酸适配体技术与纳米酶催化有效结合，通过适配体或与其它辅助分子的协同作用，对纳米酶的催化活性进行调控，同时发挥适配体对农药靶标分子的专一性识别作用，使得纳米酶催化性能在加入农药分子前后发生明显变化，在此基础上建立食品农药残留检测新方法。本项目将阐明适配体对纳米酶催化的调控机制，重点构建高活性纳米酶催化体系及其高效调控模式，确定能特异性响应农药靶标分子的传感条件，为纳米酶在其它靶标检测及生物成像等领域的应用提供理论和技术支撑。

纳米酶是一类具有催化活性的纳米材料，具有稳定性高、易大规模批量制备、比表面积大利于修饰等优势，近年来在分析化学、食品安全检测等领域得到研究人员的广泛兴趣。然而目前纳米酶存在过氧化物酶活性较低、识别特异性差、催化机制不明确等理论和技术瓶颈，还未在农药残留等检测方面得到较好应用。本项目制备了层状二硫化钨、八面体四氧化三锰、多孔四氧化三钴、立方体和八面体氧化银、带状十三氧六钒等不同形状和种类的纳米酶，并研究了模拟氧化酶、过氧化物酶催化活性和催化机制，发现显色物质和过氧化氢作为双底物参与催化时符合典型“乒乓”机制，且整个催化过程需要氧自由基的参与。研究发现乐果和草甘膦农药可以分别抑制金纳米颗粒和多孔四氧化三钴的过氧化物酶催化活性，而乐果农药又可以特异性增强立方体氧化银模拟氧化酶催化活性，从而构建基于纳米酶催化的农药检测新方法。进一步研究发现农药抑制或增强纳米酶活性的主要机制是，改变了催化体系中的羟基自由基、超氧阴离子、线性氧等氧自由基含量以及显色底物与纳米酶之间的电子转移等。本项目主要特色和创新是采用核酸适配体作为特异性识别分子，同时利用适配体调控纳米酶催化活性作为比色传感信号检测农药等危害物。研究发现适配体可以结合八面体四氧化三锰、层状二硫化钨、立方体氧化银等具有规则表面的纳米酶，通过改变纳米材料表面电荷密度等增强或抑制纳米酶的催化活性。研究揭示纳米酶种类、显色底物种类和电荷、适配体序列长度与碱基组成等，对适配体调控纳米酶活性至关重要。酶学动力学实验证实适配体抑制纳米酶活性符合非竞争和反竞争抑制类型，而适配体增强纳米酶主要机制是提高了催化体系中氧自由基含量和电子转移。此外，本项目还筛选出百草枯和氰基菊酯农药类农药的适配体，首次创建基于适配体识别的高效氯氟氰菊酯和百草枯农药检测新方法。本项目可以为食品中农药残留检测提供新思路，也为纳米酶在其它危害物检测与应用方面提供理论和技术支撑。