环境响应性纳米材料在农化控释领域研究进展

Research progress of stimuli-responsive nanomaterials on controlled-release of agrochemicals

农用化学品的滥用和不当施用对生态环境造成了极大污染,如何减少农用化学品的流失、提高其利用效率,是解决这一问题的关键。环境响应性材料是一种新型的智能材料,当环境的p H、温度、光照、磁场、氧化还原状态等发生改变时,能够响应性地发生物理或化学结构的变化。具有环境响应性的纳米材料具有智能、可控、高效等特点,已经作为药物载体被广泛应用于抗肿瘤药物的靶向释放,目前也逐渐被应用于农用化学品的控制释放。笔者综述了环境响应性纳米聚合物、微球、微胶束等材料的制备方法及其在农用化学品控制释放领域的应用,阐述了环境响应性机理,分析了环境响应性材料的形貌、化学结构、负载效率以及响应行为,并对其发展和应用前景进行了展望。环境响应性纳米材料能有效地保持农用化学品的活性或减少活性损失,从而降低用量,减少环境污染。目前相关研究尚处于起步阶段,在合成工艺和成本上仍存在诸多限制,规模化应用还需研究者持续地关注和完善。

Agrochemicals,such as pesticides,herbicides,phytohormones and fertilizers,are indispensable for agricultural production. Agrochemicals are conducive to increasing crop yields and reducing diseases. However,conventional ways of agrochemicals application are inefficient,and most of the agrochemicals are lost to soil and groundwater,which leads to the contaminations of ecological environment and bring risks of human health. In order to solve this problem,the slow-release formula was developed based on diffusion or erosion mechanism for increasing the utilization efficiency of agrochemicals,however the release process is untargeted and uncontrolled. Stimuli-responsive materials are novel'smart'materials,which can convert physical or chemical structures in response to external stimulus such as pH,thermo,light,magnetic field and redox condition. Stimuli-responsive nanomaterials has been widely used in the field of targeted drug delivery,cell culture and sensing due to their excellent performances on selectivity,controllability and biocompatibility. Recently,researchers noticed that stimuli-responsive controlled-release nanomaterials are also applicable to the release of agrochemicals in plants. Stimuli-responsive controlled-release technology facilitates the delivery of agrochemicals to targeted tissues or organs in plants,and the release rate can be regulated by adjusting the intensity of stimulus signals. This paper reviewed the preparation of thermo-,pH-,redox-,photo-,magnet-,enzymeand multi-responsive nanomaterials included polymers, microparticles, micelles, and nanogels. The mechanisms of stimuli-responsiveness were described,and the morphology,chemical structure,loading efficiency and responsive behaviors of stimuli-responsive nanomaterials were analyzed detailly. Nanomaterials can be absorbed by plants without affecting their physiological activities owing to the unique nanoscale. Stimuli-responsive nanomaterials inhibited the growth of pests and weeds as carriers of insecticides and herbicides,and the validity period was extended compared with conventional formulas;as controllable slow-release fertilizers,the damage to plant roots caused by overrelease was reduced. Although responsive materials have great potential as carriers of agrochemicals,there is still a long way to go from large-scale application due to their complicated synthesis processes and high cost. In brief,theapplication of stimuli-responsive nanomaterials in the field of controlled-release of agrochemicals is still in the early stage and needs continuous attention and research.