【作者】 刘含茂；

【导师】 徐伟箭；

【作者基本信息】 湖南大学 ， 化学工程与技术， 2009， 博士

【摘要】 分子印迹聚合物(MIPs)是一种对目标化合物具有特定识别能力的新型功能高分子材料,具有预定性、专一性和实用性等优点,且物理性质和化学性质稳定,制备过程简单,因此在色谱分离、固相萃取、生物传感器、膜分离和模拟酶催化等领域得到广泛的应用。由于MIPs具有很多优点,本文针对MIPs的制备和识别机理,以及采用分子印迹固相萃取(MISPE)从中药中分离活性成分等几方面开展工作,具体内容如下:(1)提出了一种新型的制备基于环糊精的单分散性表面分子印迹微球的方法。首先以单分散线性聚苯乙烯微球为种球,通过单步溶胀-悬浮聚合法制备了单分散交联聚甲基丙烯酸缩水甘油酯微球(PGMA),然后将β-环糊精(β-CD)和(/或)甲基丙烯酸羟乙酯与所得微球中的环氧基反应制备功能性聚甲基丙烯酸缩水甘油酯微球(F-PGMA),最后,采用表面分子印迹技术,以熊果酸(UA)为模板分子、F-PGMA为载体,制备了三种单分散表面分子印迹聚合物微球(MIMs)。采用紫外光谱和红外光谱研究了功能单体和模板分子形成主客体复合物的自组装过程。借助分子模拟对模板分子、功能单体和复合物构象进行了优化并计算了功能单体和模板分子之间的结合能。吸附动力学研究结果表明,三种MIMs对UA的吸附可以快速达到吸附平衡,这是由于含有识别位点的一薄层MIPs被接枝到多孔F-PGMA微球表面,UA容易与识别位点接近。静态吸附实验结果表明,以固载的β-CD、丙烯酰胺(AA)和二者结合所制备的MIMs具有不同的识别性能,吸附容量和印迹因子的大小顺序依次为MIMs-1(β-CD+AA)>MIMs-2(β-CD)>MIMs-3(AA),这与三种印迹体系中模板分子与功能单体之间结合能大小顺序一致。Scatchard分析结果表明MIMs-1具有两种结合位点,而相应的非印迹微球(NIMs-1)只有一种结合位点。进一步研究表明MIMs-1吸附曲线符合双结合位点模型。采用液相色谱考察了UA及其结构类似物齐墩果酸在MIMs-1上的分离的可行性,结果表明UA和齐墩果酸可以实现基线分离,而在C18柱和NIMs-1上没有得到满意的分离效果。(2)研究了MIMs-1对UA的吸附热力学。MIMs-1的吸附等温线符合Freundlich等温吸附方程。测定了UA在MIMs上吸附过程的焓变、熵变和自由能变。结果表明吸附为优惠吸附,为物理吸附过程,且为放热过程,吸附量随着温度的升高而减小。(3)研究了以MIMs-1为吸附剂从中药苦丁茶分离UA。采用样品溶液优化了固相萃取条件,从苦丁茶成功分离出较高纯度的UA。UA在MIMs-1与NIMs-1固相萃取柱上的回收率分别为96.8%和15.2%。与NIMs-1相比,MIMs-1对UA具有更好的亲和性和选择性。结果表明,将MIMs-1应用于中药中UA的富集和分离可行。(4)分别以苦参碱(MT)和其结构类似物氧化苦参碱(OMT)为模板分子制备了相应的MIPs(PM,PO)。通过红外光谱和核磁共振波谱研究了功能单体与模板分子形成复合物的自组装过程,结果表明,功能单体与模板分子之间可形成氢键作用,且它们在复合物中的化学配比为2:1。采用密度范函方法优化模板分子、功能单体以及复合物的构象,计算了功能单体与模板分子之间的结合能,并对两种MIPs的选择性进行了预测。通过静态吸附实验研究了MIPs对模板分子及类似物的识别性能。结果表明,两种MIPs对其模板分子均具有良好的吸附性能,对结构类似物的吸附性能较差。两种MIPs的亲和性与选择性与分子模拟计算所得结合能大小一致,说明分子模拟对MIPs的识别机理研究具有重要意义。Scatchard分析结果表明,两种MIPs均含有两种结合位点,对于相应的识别位点,PM的平衡离解常数大于PO的平衡离解常数,PM的最大表观结合位点数小于PO的最大表观结合位点数。这说明PM对MT的吸附能力弱于PO对OMT的吸附能力。(5)分别以PM和PO为吸附剂从中药苦参中分离苦参生物碱。采用样品溶液优化了固相萃取条件,分别从中药苦参中成功分离出较高纯度的MT和OMT。(6)制备了MT-OMT双模板MIPs(PMO),PMO对两种模板分子同时具有较好选择性吸附能力,MT和OMT的识别位点分布分别为57.71%和66.15%,交互作用的大小为23.86%。MISPE结果表明,以PMO为吸附剂能同时从苦参中分离MT和OMT。更多还原

【Abstract】 Molecularly imprinted polymers (MIPs) are novel functional materials with molecular recognition capability for target molecules. Since MIPs have the advantages of predetermination, specificity and practicability, steady physical and chemical properties, easy preparation, they have been extensively used in chromatogramphic separation, solid-phase extraction, biosensors, membrane separation and antibody mimic.Due to the advantages of MIPs, this dissertation is focused on the preparation and recognition mechanism of MIPs, and separation of bioactive compounds from traditional Chinese medicine by molecularly imprinted solid-phase extraction (MISPE). The detailed content is described as follows.(1) A novel method was reported for preparation of monodisperseβ-cyclo -dextrin(β-CD)-based surface molecularly imprinted microspheres (MIMs). Firstly, monodisperse crossing-linked poly(glycidyl methacrylate) microspheres (PGMA) were prepared by one-step swelling and polymerization method using monodisperse linear polystyrene seed particles as the shape template. Secondly, monodisperse functionalized poly(glycidyl methacrylate) microspheres (F-PGMA) were prepared throughβ-CD and (/or) hydroxyethyl methacrylate reaction with epoxy groups of PGMA. Finally, three kinds of monodisperse surface MIMs were prepared using ursolic acid (UA) as the template molecule, F-PGMA as the support matrix by a surface molecular imprinting technique. The pre-organization process of the monomer and the template was evaluated by UV and FT-IR. Molecular simulation was applied to optimize the conformations of UA, acrylamide (AA),β-CD and the complexes. The binding energy between the template and the monomer was calculated according to the single energies of UA, AA,β-CD and the complexes. The results of the adsorption dynamics study showed that the adsorption equilibrium was achieved quickly because a thin layer of MIPs containing recognition sites was grafted on the surface of the multiporous F-PGMA and the abtained MIMs showed good site accessibility for UA. The results of static adsorption experiments showed that these MIMs, prepared using bondedβ-CD and AA as the functional group/monomer, either separately or in combination, have shown various recognition properties. The adsorption capacities and imprinting factors of these MIMs were in the order of MIMs-1 (β-CD and AA) >MIMs-2 (β-CD) >MIMs-3 (AA), which was consistent with the order of the binding energies of the three kinds of imprinting systems. Scatchard analysis indicated there were two classes of affinity binding sites in MIMs-1 and one class of affinity binding site in NIMs-1. The adsorption curve of MIMs-1 was in good agreement with the two-site binding model. The feasibility of employing the MIMs-1 as the stationary phase of liquid chromatography to separate UA and OA was investigated. The results showed baseline separation was achieved on the imprinted column, but the non-imprinted column and C18 column could not achieve.(2) The adsorption thermodynamics of UA on MIMs-1 were investgated. The adsorption isotherms were fitted with Freundlich isotherms. The enthalpy change, entropy change and free energy change were estimated. The results indicated that the adsorption was a favourable, physical and radiative adsorption process. The adsorption capacity decreased with the increase of the solution temperature.(3) Separation of UA from Chinese traditional medicine, Ilex kudingcha C. J. Tseng, using MIMs-1 as the adsorption materials was investigated detailedly. The conditions of solid-phase extraction were optimized using sample solution, and relatively pure UA was obtained. The recoveries of UA on MIMs-1and NIMs-1 were 96.8% and 15.2%, respectively. Compared with NIMs-1, MIMs-1 had higher affinity and selectivity to UA. It shows the possibility for application of MIMs-1 as a selective adsorbent for enrichment and isolation of UA from herbs.(4) Two kinds of MIPs (PM, PO) were prepared using matrine (MT) and its structural analogue oxymatrine (OMT) as the template, respectively. The pre-organization process of the monomer and the template was evaluated by IR and 1H NMR. The results indicated that hydrogen bonds formed between the template and the monomer of the two MIPs, and the stoichiometric mole ratio of the template-monomer complexe was 1:2. The conformations of the template, the monomer and the complex were optimized by density functional theory, and the binding energy between the monomer and the template molecule was calculated. The affinity and selectivity of the two MIPs were also predicted by molecular simulation. Recongition properties of two MIPs were investigated by static adsorption experiments. The results indicated they showed good recongition properties for their own template, and relative poor for the analogues. The affinity and selectivity performances of the two kinds of MIPs consisted with the binding energies calculated by molecular simulation, which indicated molecule simulation had important meanings for understanding the recongnition mechanism of MIPs. Scatchard analysis was applied to study the recongnition mechanism of MIPs. The results of scatchard analysis indicated that there were two kinds of binding sites in each MIPs. The equilibrium dissociation constants of the lower and higher affinity binding sites of PM were more than those of PO, and the apparent maximum numbers of binding sites of the lower and higher affinity binding sites of PM were lower than those of PO for the corresponding binding sites. It indicated the adsorption capability of PM for MT was lower than that of PO for OMT.(5) Separation of MT and OMT from Sophora flavescens Ait using PM and PO as the adsorbents, respectively. The conditions of solid-phase extraction were optimized using sample solution. Relatively pure MT and OMT were obtained, respectively.(6) Two-template MIPs (PMO) were prepared using MT and OMT as the mixed template. PMO has shown good recognition ability for MT and OMT simultaneously. The distributions of recognition sites for MT and OMT were 57.71% and 66.15%, respectively, and the distribution of the cross reactivity binding sites was 23.86%. The results of MISPE indicated that MT and OMT could be separated simultaneously from Sophora flavescens Ait using PMO as the adsorbent.更多还原