Surface molecular imprinting in layer-by-layer films on silica particles

An improvement to molecular imprinting in polymers, where bulk systems often suffer from slow dynamics of release and uptake, is the formation of thin films with imprinting sites that are more rapid to access by guest molecules. Based on our previous development of surface molecular imprinting layer-by-layer (LbL) films (SMILbL), the present paper presents selective imprinted sites in a surface film on dispersed silica particles, thus designing a SMILbL system with maximized active area and in addition allowing studies with bulk techniques. The multilayer is designed to include the template during the LbL buildup and to form a cross-linked network upon UV-irradiation for enhanced stability. A theophylline moiety is grafted to poly(acrylic acid) as the template, while a UV-sensitive diazo polycation cross-links the polymers after irradiation. Electrophoretic measurements prove the successful buildup of the multilayers by an alternating sign of the zeta potential. Template release is achieved by cleavage of the grafted template. The released amount of template is quantified in solution by (1)H NMR spectra and is in good agreement with the prediction from surface coverage calculations. Rebinding studies of template to the now empty imprinted binding sites show a high affinity for a theophylline derivative with a rebound amount on the order of the original template content. In contrast to theophylline, caffeine with a very similar chemical structure-only differing in one functional group-shows very different binding properties due to a thiol moiety in the binding site. Thus, a particle system with very selective molecular imprinting sites is demonstrated.     

表面印迹交替层状组装薄膜

在简要概述非常规交替层状组装这一进展后,重点总结了如何利用非常规交替层状组装以实现表面印迹膜的制备.模板分子与聚电解质在溶液中组装形成超分子复合物,然后以此超分子复合物为构筑基元,与感光性高分子,如重氮树脂,通过常规交替层状组装形成聚合物多层膜.利用聚合物多层膜之间的光化学反应形成稳定的多层膜,然后去除模板分子得到分子...     

Nanotemplating for two-dimensional molecular imprinting

A new 2D molecular imprinting technique based on nanotemplating and soft-lithography techniques is reported. This technique allows the creation of target-specific synthetic recognition sites on different substrates using a uniquely oriented and immobilized template and the attachment of a molecularly imprinted polymer on a substrate. The molecularly imprinted polymer was characterized by AFM, fluorescence microscopy, and ATR-FTIR. We evaluated the rebinding ability of the sites with theophylline (the target molecule). The selectivity of the molecularly imprinted polymer was determined for the theophylline-caffeine couple. The molecularly imprinted polymer exhibited selectivity for theophylline, as revealed by competitive rebinding experiments. Fluorescence microscopy experiments provided complementary proof of the selectivity of the molecularly imprinted polymer surfaces toward theophylline. These selective molecularly imprinted polymers have the potential for chemical sensor applications. Because of its 2D nature, this novel chemical sensor technology can be integrated with many existing high-sensitivity multichannel detection technologies.     

环丙沙星分子印迹聚合物的合成及识别性能研究

采用分子印迹技术合成了以环丙沙星为印迹分子,以甲基丙烯酸和4-乙烯基吡啶同时为功能单体的分子印迹聚合物。运用平衡结合实验研究了印迹聚合物的吸附特性和选择识别能力。Scatchard分析表明,在所研究的浓度范围内,分子印迹聚合物中形成了两类不同的结合位点。底物选择实验表明,这种聚合物对环丙沙星呈现高的选择结合能力。     

Core-shell nanostructured molecular imprinting fluorescent chemosensor for selective detection of atrazine herbicide

To convert the binding events on molecularly imprinted polymers (MIPs) into physically detectable signals and to extract the templates completely are the great challenges in developing MIP-based sensors. In this paper, a core-shell nanostructure was employed in constructing the MIP chemosensor for the improvements of template extraction efficiency and imprinted sites accessibility. Vinyl-substituted zinc(II) protoporphyrin (ZnPP) was used as both fluorescent reporter and functional monomer to synthesize atrazine-imprinted polymer shell at silica nanoparticle cores. The template atrazine coordinates with the Lewis acid binding site Zn of ZnPP to form a complex for the molecular imprinting polymerization. These imprinted sites are located in polymer matrix of the thin shells (~8 nm), possessing better accessibility and lower mass-transfer resistance for the target molecules. The fluorescence properties of ZnPP around the imprinted sites will vary upon rebinding of atrazine to these imprinted sites, realizing the conversion of rebinding events into detectable signals by monitoring fluorescence spectra. This MIP probe showed a limit of detection (LOD) of about 1.8 μM for atrazine detection. The core-shell nanostructured MIP method not only improves the sensitivity, but also shows high selectivity for atrazine detection when compared with the non-molecular imprinted counterparts.     

Carbohydrate recognition by porphyrin-based molecularly imprinted polymers

[structure: see text] Porphyrin-based molecularly imprinted polymers (MIPs) were prepared for carbohydrate recognition. A urea-appended porphyrin functional monomer was utilized to provide complementary functionality and quality binding sites throughout the polymer. Each porphyrin-based polymer demonstrates high affinity and differential selectivity for closely related carbohydrates that correlate to the structure of the template used in the imprinting process.     

Surface molecular imprinted layer-by-layer film attached to a porous membrane for selective filtration

A surface molecular imprinted layer-by-layer (SMILbL) film was fabricated on a polyethersulfone (PES) porous membrane substrate for selective filtration of cations and anions. The LbL deposition procedure and the ultraviolet (UV) cross-linking of the modified membrane were monitored by attenuated total reflection-infrared (ATR-IR) spectra. The SMILbL-PES membrane with 4.5 bilayers of diazoresin (DAR)/poly(acrylic acid) complexed with 5,10,15,20-tetrakis(4-(trimethylammonio)-phenyl)-21H,23H-porphyrin tetratosylate (PAA-Por(4+)) effectively reduced the permeation velocity of Por(4+) after washing the Por(4+) template out. In comparison to a control film DAR/PAA-modified PES membrane (ConLbL-PES) in a dialysis experiment, the SMILbL-PES membrane exhibited better selectivity for permeation of 5,10,15,20-tetraphenyl-21H,23H-porphine-p,p',p″,p?-tetrasulfonic acid tetrasodium hydrate (Por(4-)) against permeation of Por(4+). In pressure-driven transport experiments, the SMILbL-PES membrane showed a much longer blocking time for Por(4+) than for Por(4-), indicating the selective loading of Por(4+) into the SMILbL film. The surface charge of the SMILbL-PES membrane after Por(4+) loading was higher than that of other membranes, resulting in an enhanced rejection ability of the SMILbL-PES membrane to Por(4+) caused by Coulomb repulsion. A possible mechanism was proposed as follows. The binding sites generated through imprinting in the SMILbL-PES membrane enable loading of a larger amount of Por(4+). The stronger repulsion between Por(4+) and the SMILbL film may cause the main contribution to the selective rejection of Por(4+). It can be easily imagined that this concept can be extended to the construction of composite membranes from other imprinting systems.     

基于N-异丙基丙烯酰胺的温敏型分子印迹聚合物

温敏型分子印迹技术是近几年来分子印迹技术新的发展。温敏型分子印迹聚合物以低交联度为特征,对模板分子的吸附容量和选择性随温度变化而改变。本文总结并评述了基于N-异丙基丙烯酰胺的温敏型MIP分子印迹聚合物及其制备方法,指出了温敏型分子印迹技术发展中需要解决的问题。     

Enantioselective sensor based on microgravimetric quartz crystal microbalance with molecularly imprinted polymer film

We report a novel quartz crystal microbalance sensor that provides enantioselectivity to dansylphenylalanine enantiomers by using a molecularly imprinted polymer film as a recognition element. The polymeric recognition thin film, imprinted with chiral dansyl-L-phenylalanine, was immobilised on a gold electrode modified with a photoactive precursor monolayer via a self-assembly process using photopolymerization. The fabricated sensor was able to discriminate between L- and D-dansylphenylalanine enantiomers in solution owing to the enantioselectivity of the imprinted sites. The enantiomeric composition of L- and D-enantiomeric mixtures could be quantitatively determined by the fabricated sensor. The detection limit is 5 micrograms mL-1 with a response range of 5-500 micrograms mL-1 at pH 10.0. The influence of the template concentration on the sensitivity and selectivity of the synthesised polymer membranes was investigated and optimised. The surface characteristics of the polymer coating were studied by varying the pH value of the buffer solution, and a convenient regeneration process was proposed to increase the reproducibility and reusability of the sensor by flushing with pH 2.0 buffer. The selectivity and recognition mechanism of the imprinted polymer film were studied with compounds that are structurally related to the template. The method presented in this work provides a novel means of preparing highly selective and sensitive chemical sensors via self-assembly and molecularly imprinting techniques.     

酚酞分子印迹聚合物的制备及特异吸附性能

以泻药酚酞为模板分子,4-乙烯基吡啶为功能单体制备了模板分子和功能单体不同比例的一系列酚酞分子印迹聚合物。利用扫描电镜对聚合物进行了表面形态分析,采用静态平衡实验法研究了聚合物对模板分子及其类似物的吸附行为和选择性识别能力。实验结果表明,所制备的分子印迹聚合物,吸附 3 h 后基本接近最大吸附量,其中模板分子、4-乙烯基吡啶和交联剂的摩尔比为 1∶6∶20的MIP2的印迹因子为 2.30,效果最佳。Scatchard 分析表明, 在所研究的浓度范围内,吸附过程存在两类结合位点,一类高亲和力结合位点的离解常数为Kd1= 0.63 mmol/L,最大表观结合量 Qmax1 = 25.4 umol/g,另一类低亲和力结合位点的离解常数为 Kd2 =3.5 mmol/L,最大表观结合量 Qmax2 = 61.9 umol/g,通过与酚酞类似物质在酚酞分子印迹聚合物上的吸附行为比较,表明对酚酞具有很好的选择性吸附。     

牛血清白蛋白在超薄纳米二氧化钛膜表面的印迹与吸附

基于溶胶凝胶分子印迹方法,以溶胶二氧化钛TiO2为基质印迹了牛血清白蛋白分子。用1%的NaOH溶液可有效地除去纳米TiO2印迹膜中的模板分子。采用石英晶体微天平现场技术,研究了牛血清白蛋白在超薄纳米TiO2膜表面的吸附行为。研究表明,牛血清白蛋白在印迹膜和非印迹膜上的吸附量都随溶液浓度增加而增大,印迹膜具有吸附的特异性和可再生性,其吸附量是非印迹膜的3~5倍;在非印迹膜上的吸附符合Langmuir吸附模型,而在印迹膜上的吸附符合allosteric吸附模型;牛血清白蛋白在非印迹膜上的吸附量先随pH升高而增大,当pH为5左右时达到最大值,随后吸附量又随pH的增大而减小;而在印迹膜上其吸附量仅随pH增大而增大。     

Two-dimensional molecular imprinting approach to produce optical biosensor recognition elements

This article describes a new two-step methodology for preparing thiol monolayers having artificial recognition sites for dansylated amino acids on gold optical biosensor surfaces. Nepsilon-Dansyl-L-lysine (DK) was used as the template molecule to form molecularly imprinted monolayers (MIMs). Impact factors that were studied were the concentration of DK in step one (template deposition) and the time and method for thiol monolayer formation in step two (backfilling). Compared to a prior method that used the simultaneous adsorption of the template and thiol from solution, this new approach provides the flexibility to imprint template molecules that have low binding energies on gold. Control over the surface density of imprinting sites can be achieved by this approach, and rebinding studies done using surface plasmon resonance spectroscopy confirmed that the MIMs prepared against DK showed selectivity for that template over didansyl-L-lysine.     

表面分子(离子)印迹硅胶/聚合物的制备及性能研究进展

分子印迹技术(MIT)是制备对模板分子具有专一识别能力聚合物的技术。目前,把识别位点建立在基质表面的表面印迹技术日益受到重视,它可以提高识别位点与印迹分子的结合速度,进一步加强印迹材料吸附分离效率,硅胶因其具有良好的机械稳定性和热稳定性,吸附选择性高等优点,作为表面印迹的基质显示出较大的优越性。本文详细综述了有机分子印迹硅胶/聚合物及金属离子印迹硅胶/聚合物的制备和性能的研究进展,并对印迹材料将来的应用进行了展望。     

核-壳型厚朴酚印迹聚合物的制备及性能研究

以表面修饰功能基团的SiO2微球为基体,以厚朴酚为模板分子,丙烯酰胺为功能单体,丙烯酸乙二醇二甲酯为交联剂,在SiO2微球表面制备对厚朴酚具有较好选择识别能力的核-壳型印迹聚合物.采用红外光谱及扫描电镜等技术表征聚合物的结构及形态.结果表明,该印迹聚合物表面成功制备了壳层厚度约为200nm的均匀印迹层.通过静态吸附、Scatchard分析法以及竞争吸附实验研究了该聚合物的吸附性能和选择性,结果表明,它对厚朴酚形成均一结合位点,离解常数为0.19mg/mL.     

Preparation of a stoichiometric molecularly imprinted polymer for auramine O and application in solid‐phase extraction

We describe a stoichiometric approach to the synthesis of molecularly imprinted polymers specific for auramine O. Using the stoichiometric interaction in molecular imprinting, no excess of binding sites is necessary and binding sites are only located inside the imprinted cavities. The free base of the template was obtained to facilitate the interaction with the monomers. Itaconic acid was selected as the functional monomer, and stoichiometric ratio of the interaction with the free base was investigated. The molecularly imprinted polymer preparation conditions such as cross‐linker, molar ratio, porogen were optimized as divinylbenzene, 1:2:20 and chloroform/N,N‐dimethylformamide, respectively. Under the optimum conditions, a good imprinting effect and very high selectivity were achieved. A solid‐phase extraction method was developed using the molecularly imprinted polymers as a sorbent and extraction procedure was optimized. The solid‐phase extraction method showed a high extraction recovery for auramine O in its hydrochloride form and free form compared to its analogues. The results strongly indicated that stoichiometric imprinting is an efficient method for development of high selectivity molecularly imprinted polymers for auramine O.     

Interfacial Molecular Imprinting in Nanoparticle-Stabilized Emulsions

A new interfacial nano and molecular imprinting approach is developed to prepare spherical molecularly imprinted polymers with well-controlled hierarchical structures. This method is based on Pickering emulsion polymerization using template-modified colloidal particles. The interfacial imprinting is carried out in particle-stabilized oil-in-water emulsions, where the molecular template is presented on the surface of silica nanoparticles during the polymerization of the monomer phase. After polymerization, the template-modified silica nanoparticles are removed from the new spherical particles to leave tiny indentations decorated with molecularly imprinted sites. The imprinted microspheres prepared using the new interfacial nano and molecular imprinting have very interesting features: a well-controlled hierarchical structure composed of large pores decorated with easily accessible molecular binding sites, group selectivity toward a series of chemicals having a common structural moiety (epitopes), and a hydrophilic surface that enables the MIPs to be used under aqueous conditions.     

模板结构与分子印迹效果间关系的研究

以一些分子量和体积都较小的简单化合物作为模板分子,合成分子印迹聚合物 。通过总结43种化合物的分子印迹聚合物的色谱数据,来研究模板分子的分子量、 作用位点数目、分子刚性等因素与印迹效果的关系。根据免疫学中免疫原性的定义 ,我们提出“印迹原性”的概念,即,化合物能够产生印迹效应的性质称为印迹原 性;具有印迹原必的化合物称为印迹原;并讨论了具有较强选择性的印迹原的化学 基础。所得到的结论将有助于对分子印迹聚合物的识别机理的进一步理解,并且对 于根据模板分子性质预测MIP分子识别能力将具有一定的指导意义。     

分子印迹聚合物膜对氨基酸海因手性化合物的选择性结合和透过性质研究

合成了可对氨基酸海因对映异构体选择性分离的分子印迹聚合物膜。利用紫外光谱法比较不同功能单体与模板分子的作用能力。以丙烯酰胺为功能单体,在极性溶剂中制备了5R-5氨-基酸海因的分子印迹聚合物膜,通过Scatchard分析法研究膜中结合位点情况。通过膜透过实验研究印迹膜对外消旋体的分离特性。Scatchard分析显示聚合物膜中形成了两类结合位点,其解离常数分别为1.88mmol/L和5.14mmol/L;选择性透过实验表明膜中形成了与5R-5氨-基酸海因分子形状和功能基因位置匹配的孔穴。与非印迹聚合物膜相比,印迹聚合物膜对对映体具有良好的选择性。     

尼卡地平分子聚合物的制备及识别性能研究

采用分子印迹技术合成了以尼卡地平为模板分子,甲基丙烯酸为功能单体的分子印迹聚合物(MIP).运用平衡结合实验研究了聚合物的吸附特性和选择识别能力.通过Scatchard方程分析,结合位点的离解常数Kd=1.03 mmol·L-1,最大表观结合常数Qmax=18.76 μmol·g-1.结果表明,分子印迹聚合物对尼卡地平呈现出较高的吸附性和选择识别性,对尼卡地平药物的分离富集和检测具有实际临床意义.     

A molecularly imprinted photonic polymer sensor with high selectivity for tetracyclines analysis in food

A molecularly imprinted photonic polymer (MIPP) sensor for respective detection of tetracycline, oxytetracycline and chlortetracycline is developed based on the combination of a colloidal crystal templating method and a molecular imprinting technique. Colloidal crystal templates are prepared from monodisperse polystyrene colloids. The molecularly imprinted polymer, which is embodied in the colloidal crystal templates, is synthesized with acrylic acid and acrylamide as monomers, N,N'-methylene bisacrylamide as a cross-linker and tetracyclines (TCs) as imprinting template molecules. After removal of the colloidal crystal template and the molecularly imprinted template, the resulted MIPP consists of a three-dimensional, highly ordered and interconnected macroporous array with a thin hydrogel wall, where nanocavities complementary to analytes in shape and binding sites are distributed. The response of MIPP to TCs stimulants in aqueous solution is detected through a readable Bragg diffraction red-shift, which is due to the lattice change of MIPP structures responding to their rebinding to the target TCs molecules. A linear relationship was found between the Δλ and the concentration of TCs in the range from 0.04 μM to 0.24 μM. With this sensory system, direct and selective detection of TCs has been achieved without using label techniques and expensive instruments. The developed method has been applied successfully to detect tetracycline in milk and honey samples.