摘要
分子印迹是制备对某一客体分子具有预定选择性的聚合物材料过程,最初起源于Fischer的“锁钥学说”和Pauling的抗体形成学说。利用分子印迹聚合物内所形成的与模板分子相匹配的形状、孔穴大小、识别位点等,对模板分子产生的“识别效应”来实现对模板分子的选择性识别。分子印迹聚合物不仅具有类似酶和抗体的特定的识别能力,而且还具有独特的化学和物理稳定性、长的使用寿命和简单的制备方法等优点,因此,它已获得广泛的应用,包括色谱固定相、模拟酶催化、固相萃取、药物传递和传感技术等。
分子印迹膜结合了分子印迹技术和膜分离技术的优点,具有操作简便,耗能少,反应时间短,干净无污染等特点,同生物膜相比,具有很高的稳定性和机械强度,对目标分子具有高的渗透选择性和识别能力。
农药残留危害已越来越引起了人们的重视,“十一五”开局的2006年,国家863计划将分子印迹技术在农药检测领域的应用作为重点技术进行支持,当前研究和加快农药快速检测方法的建立对于食品安全迫切需要也是世界各国政府和人民的共同愿望。
本文合成了N,O-双异丁烯酰乙醇胺作交联功能单体,利用分光光度法研究了甲醇中N,O-双异丁烯酰乙醇胺和苯磺隆的结合机理,基于此,制备合成了以苯磺隆为模板分子的分子印迹膜,我们用扫描电镜观测了所制得分子印迹膜和非分子印迹膜的表面形态。我们还测定了分子印迹膜的印迹因子,并通过单分子渗透实验和多分子竞争扩散实验检验了分子印迹膜对苯磺隆、噻吩磺隆和氯嘧磺隆的选择渗透性,实验结果表明,制备的分子印迹膜对模板分子苯磺隆具有高选择性。
通过表面引发的原子转移自由基聚合作用,合成了分子印迹纳米线膜,用扫描电镜观测了所制得分子印迹纳米线膜和非分子印迹膜的表面形态。绘制了分子印迹纳米线膜对模板分子的吸附等温线,用Scatchard图验证了分子印迹纳米线膜对苯磺隆的结合特性。通过单分子渗透实验和多分子竞争扩散实验检验了分子印迹膜对苯磺隆、噻吩磺隆、氯嘧磺隆和氯对溴的选择渗透性,实验结果表明,制备的分子印迹膜对模板分子苯磺隆具有高选择性。
在制备分子印迹膜的过程中,省去了额外功能单体的加入和功能单体、交联剂和模板配比的优化,大大简化了理想分子印迹聚合物的制备手续,与传统的功能单体相比对模板分子具有更明显的选择性。这种识别特性有望实现建立残留快速检测的传感技术,对于建立农药残留的快速检测方法具有一定的指导意义。
Molecular imprinting is a method that can prepare polymer material with predetermined selectivity towords guest molecules. This technique camed from Fischer’s lock-and-key hypothesis and Pauling’s antibody-forming theory. Taking advantage of the shape, size, functional groups corresponding to the template molecule inside the molecularly imprinted polymer, the selectively recognization for the tribenuron-methyl was realized through for template molecule. Molecularly imprinted polymer not only has specific recognization like enzyme and antibody, but also has other advantages like specific chemical and physical stability, long working life, simple preparation methods. Consequently, it was widely applied such as chromatographic stationary phase, enzyme-micing catalysis, solid phase extraction (SPE), drug delivery system(DDS), and sensing technology.
Molecularly imprinted membranes combine the advantages of molecular imprinting and membrane separation. It also has specialty such as simple operation, less energy, short reaction time, clean, uncontaminated, high stability, good mechanical properties, high permselectivity and recognization capability compared with biological membrane.
The hazard of pesticide residual has aroused more and more people’s attention. In the year 2006, the beginning of Eleventh Five-year Plan, molecular imprinting technique as a key program applied in the field of pesticide detection has been supported by National 863 Plan. At present it is a urgent need for food security to research and improve rapid detection method, and also a common desire for governments and people.
In this paper, N,O-bismethacryloyl ethanolamine was synthesized as crosslinking monomer, then the binding mechanism between N,O-bismethacryloyl ethanolamine and tribenuron-methyl in methanol was studied with UV-visible spectrophotometer. Based on this study, using tribenuron-methyl as template molecule, molecularly imprinted membrane was prepared. Then, morphologies of the resultant polymeric membrane or the control membrane were visualized with scanning electron microscopy (SEM), and the imprinting factor was also detected. The membrane permselectivity for tribenuron-methyl, thifensulfuron-methyl and chlorimuron-ethyl was tested with separate experiments and competitive diffusion experiments. These results showed that the molecularly imprinted membrane exhibited higher transport selectivity for the template molecule tribenuron-methyl.
Then, molecularly imprinted nanowire membrane was prepared through surface-initiated atom transfer radical polymerization (ATRP), and the morphologies of the prepared molecularly imprinted nanowire membrane and the control membrane was observed. The adsorption isotherm of the molecularly imprinted nanowire membrane toward the template molecule was drawed, and the associated property of the molecularly imprinted nanowire membrane toward tribenuron-methyl was confirmed using Scatchard equation. The membrane permselectivity for tribenuron-methyl, thifensulfuron-methyl, chlorimuron-ethyl and BCIA was tested with separate experiments and competitive diffusion experiments. These results showed that the olecularly imprinted membrane exhibited higher transport selectivity for the template molecule tribenuron-methyl.
In the process of preparing molecularly imprinted membrane, the preparation procedure was simplified greatly by ignoring the optimum ratio of functional monomer/cross-linker, and the optimum ratio of functional monomer/template. Utilization of NOBE alone often provides molecularly imprinted polymers with higher affinity toward templates than those of incorporating a functional monomer. This selective identification feature will help to develop sensor technique in rapid detection of tribenuron-methyl residual, and it is of some guiding significance for settling rapid detection method of pesticide residual.
引文
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