Preparation of quercetin imprinted core-shell organosilicate microspheres using surface imprinting technique

In this work,the quercetin imprinted core-shell microspheres were prepared using silica surface imprinting technique.A simple sol-gel procedure was used for the synthesis of the imprinted materials with 3-aminopropyltriethoxysilane as functional monomer and tetraethyl orthosilicate as crosslinker.The SEM images indicated that the MIPs shell was successfully grafted onto the silica surface.The characteristics of the molecularly imprinted polymers such as capacity,selectivity and absorption dynamic were investigated by rebinding experiments.The results showed that the prepared MIPs had good imprinting effect and adsorption amount of quercetin.     

The effectively specific recognition of bovine serum albumin imprinted silica nanoparticles by utilizing a macromolecularly functional monomer to stabilize and imprint template

Structural stability of the template is one of the most important considerations during the preparation of protein imprinting technology. To address this limitation, we propose a novel and versatile strategy of utilizing macromolecularly functional monomers to imprint biomacromolecules. Results from circular dichroism and synchronous fluorescence experiments reflect the macromolecularly functional monomers tendency to interact with the protein surface instead of permeating it and destroying the hydrogen bonds that maintain the protein’s structural stability, therefore stabilizing the template protein structure during the preparation of imprinted polymers. The imprinted polymers composed of macromolecularly functional monomers or their equivalent micromolecularly functional monomers over silica nanoparticles were characterized and carried out in batch rebinding test and competitive adsorption experiments. In batch rebinding test, the imprinted particles prepared with macromolecularly functional monomers exhibited an imprinting factor of 5.8 compared to those prepared by micromolecularly functional monomers with the imprinting factor of 3.4. The selective and competitive adsorption experiments also demonstrated the imprinted particles made by macromolecularly functional monomers possessed much better selectivity and specific recognition ability for template protein. Therefore, using macromolecularly functional monomers to imprint may overcome the mutability of biomacromolecule typically observed during the preparation of imprinted polymers, and thus promote the further development of imprinting technology.     

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.     

Via protoporphyrin to the synthesis of levofloxacin‐imprinted polymer

A new molecularly imprinted polymer (MIP) for levofloxacin was prepared by the combined use of methacrylic acid and protoporphyrin as functional monomers. The adsorption properties of resultant imprinted polymers were evaluated by equilibrium rebinding experiments. The highest binding capacity of levofloxacin achieved from the optimized imprinted polymer in acetonitrile was 246.26 µmol/g with an imprinting factor of 2.05. A ?uorescence quenching effect was observed when a protoporphyrin‐based imprinted polymer was incubated in the solutions of levofloxacin. The results indicated that the protoporphyrin‐based MIPs were able to create higher binding cavities for template compared with MIPs using only methacrylic acid as a functional monomer. It should be expected that the cooperative use of the protoporphyrin with supplemental different functional monomers may be an alternative to obtain MIP with the improvement of the selectivity. Copyright © 2010 John Wiley & Sons, Ltd.     

Cost‐effective imprinting combining macromolecular crowding and a dummy template for the fast purification of punicalagin from pomegranate husk extract

The combination of molecular crowding and virtual imprinting was employed to develop a cost‐effective method to prepare molecularly imprinted polymers. By using linear polymer polystyrene as a macromolecular crowding agent, an imprinted polymer recognizable to punicalagin had been successfully synthesized with punicalin as the dummy template. The resulting punicalin‐imprinted polymer presented a remarkable selectivity to punicalagin with an imprinting factor of 3.17 even at extremely low consumption of the template (template/monomer ratio of 1:782). In contrast, the imprinted polymer synthesized without crowding agent, did not show any imprinting effect at so low template amount. The imprinted polymers made by combination of molecular crowding and virtual imprinting can be utilized for the fast separation of punicalagin from pomegranate husk extract after optimizing the protocol of solid‐phase extraction with the recovery of 85.3 ± 1.2%.     

Preparation and Cyclic Voltammetry Characterization of Cu—dipyridyl Imprinted Polymer

Polymer capable of specific binding to Cu-dipyridyl complex was prepared by molecular imprinting technology. The binding specificity of the polymer to the template (Cu-dipyridyl complex) was in vestigated by cyclic voltametric scanning using the carbon paste electrode modified by polymer particles in phosphate buffer solution. Factors that influence rebinding of the imprinted polymer were explored. The result demonstrated that the cycllic voltammetry was an efficient approach to explore interactions between template and imprinted polymers.     

Molecular imprinting in alcohols: utility of a pre-polymer based strategy for synthesizing stereoselective artificial receptor polymers in hydrophilic media

Molecular imprinting using a linear pre-polymer bearing carboxylic and 4-vinylbenzyl residues was performed in alcohols for synthesizing stereoselective polymer receptors. Chromatographic assessment of the imprinted polymers, which are obtained by cross-linking the pre-polymer in the presence of a model template (−)-cinchonidine, showed the induction of affinity and selectivity to the template species by the imprinting procedure. Comparison with the performance of an imprinted polymer prepared with a monomer mixture instead of the pre-polymer elucidated the efficacy of the linear pre-polymer for molecular imprinting in the protic solvents.     

Adaptation of the molecular imprinted polymers towards polar environment

A new simple method for the post-polymerisation treatment of molecularly imprinted polymers was proposed. A layer of mineral oil was deposited onto the surface of the polymer in order to create a hydrophobic environment in the binding sites and to improve the recognition properties of the polymer in polar solvents. The testing of polymers performed in acetonitrile showed that the modified polymers possessed significantly increased selectivity as compared with non-treated ones. The three-fold improvement of recognition of the template (cocaine) was achieved; the same time, for non-specific molecule (morphine) the improvement was only 1.3 times. The investigation of the stability of mineral oil coating on the polymer surface suggested that the effect produced is stable over a long period of time. This approach could be used to broaden the range of experimental conditions where molecularly imprinted polymers can perform successfully.     

Selective enrichment and separation of phosphotyrosine peptides by thermosensitive molecularly imprinted polymers

Novel thermosensitive molecularly imprinted polymers were successfully prepared using the epitope imprinting approach in the presence of the mimic template phenylphosphonic acid, the functional monomer vinylphosphonic acid‐Ti⁴⁺, the temperature‐sensitive monomer N‐isopropylacrylamide and the crosslinker N,N′‐methylenebisacrylamide. The ratio of the template/thermosensitive monomers/crosslinker was optimized, and when the ratio was 2:2:1, the prepared thermosensitive molecularly imprinted polymers had the highest imprinting factor. The synthetic thermosensitive molecularly imprinted polymers were characterized by Fourier transform infrared spectroscopy to reveal the combination and elution processes of the template. Then, the adsorption capacity and thermosensitivity was measured. When the temperature was 28°C, the imprinting factor was the highest. The selectivity and adsorption capacity of the thermosensitive molecularly imprinted polymers for phosphotyrosine peptides from a mixture of three tailor‐made peptides were measured by high‐performance liquid chromatography. The results showed that the thermosensitive molecularly imprinted polymers have good selectivity for phosphotyrosine peptides. Finally, the imprinted hydrogels were applied to specifically adsorb phosphotyrosine peptides from a sample mixture containing phosphotyrosine and a tryptic digest of β‐casein, which demonstrated high selectivity. After four rebinding cycles, 78.9% adsorption efficiency was still retained.     

Scalemic and racemic imprinting with a chiral crosslinker

The development of molecularly imprinted chiral stationary phases has traditionally been limited by the need for a chiral pure template. Paradoxically, availability of a chiral pure template largely defeats the purpose of developing a chiral stationary phase. To solve this paradox, imprinting of scalemic and racemic template mixtures was investigated using both chiral (N-α-bismethacryloyl-l-alanine) and achiral (N,O-bisacrylamide ethanolamine) crosslinkers. Imprinting of scalemic mixtures provided polymers capable of partial separation of Boc-tyrosine enantiomers with virtually the same results when using either the chiral or achiral crosslinker. However, the chiral crosslinker was required for chiral differentiation by the racemic imprinted polymers which were evaluated in both batch rebinding and chromatographic modes. Batch rebinding analysis revealed intersecting binding isotherms for the L- and D-Boc-tyrosine, indicating bias for the D or L enantiomer is concentration dependent. Partial chromatographic separation was achieved by the racemic imprinted polymers providing variable D or L bias in equal probability over multiple replicates of polymer synthesis. Correlation of enantiomer bias with the batch rebinding results and optimization of HPLC parameters are discussed.     

Design of EGDMA‐Crosslinked Theophylline Imprinted Polymer with High Specificity and Selectivity

An attempt has been made to design theophylline selective polymers with maximum selectivity and specificity, and to relate the rebinding capacity of the polymers with the degree of crosslinking, as well as with the template‐monomer ratio. The theophylline imprinted and non‐imprinted polymers based on methacrylic acid as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking agent (35–80 mol%) were prepared. The developed imprinted polymers were characterized by FT‐IR, ¹H and ¹³C‐NMR spectra. Equilibrium binding of theophylline by the imprinted and non‐imprinted polymers were investigated and optimized the conditions. Imprinted polymers showed specific binding of the template theophylline. Selectivity of the imprinted polymers was investigated towards caffeine and nicotine. Imprinted polymers showed specific and selective binding of theophylline, which varied with the degree of EGDMA crosslinking. Equilibrium rebinding experiments proved that imprinted polymer with moderate (70%) crosslinking with 1∶2 template‐functional monomer ratio is ideal with maximum specificity and selectivity.     

Comparison of molecular imprinted particles prepared using precipitation polymerization in water and chloroform for fluorescent detection of nitroaromatics

A comparative study was conducted to study the effects that two different polymerization solvents would have on the properties of imprinted polymer microparticles prepared using precipitation polymerization. Microparticles prepared in chloroform, which previous results indicated was the optimal solvent for molecular imprinting of nitroaromatic explosive compounds, were compared to water, which was hypothesized to decrease water swelling of the polymer and allow enhanced rebinding of aqueous template. The microparticles were characterized and were integrated into a fluorescence sensing mechanism for detection of nitroaromatic explosive compounds. The performance of the sensing mechanisms was compared to illustrate which polymerization solvent produced optimal imprinted polymer microparticles for detection of nitroaromatic molecules. Results indicated that the structures of microparticles synthesized in chloroform versus water varied greatly. Sensor performance studies showed that the microparticles prepared in chloroform had greater imprinting efficiency and higher template rebinding than those prepared in water. For detection of 2,4,6-trinitrotoluene, the chloroform-based fluorescent microparticles achieved a lower limit of detection of 0.1 μM, as compared to 100 μM for the water-based fluorescent microparticles. Detection limits for 2,4-dinitrotoluene, as well as time response studies, also demonstrated that the chloroform-based particles are more effective for detection of nitroaromatic compounds than water-based particles. These results illustrate that the enhanced chemical properties of using the experimentally determined optimal polymerization solvent overcome deformation of imprinted binding sites by water swelling and benefits of using the polymerization solvent for rebinding of the template.     

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。     

Noncovalently galactose imprinted polymer for the recognition of different saccharides

Molecularly imprinted polymers (MIPs) represent a new class of materials possessing high selectivity and affinity for the target molecule. The main goal of this study was to prepare a galactose imprinted polymer and its potential application for the recognition of different saccharides. The selectivity of galactose imprinted polymer for several saccharides; glucose, mannose, fructose, maltose, lactose, sucrose and raffinose was investigated. Macroporous polymer was prepared utilizing ethyleneglycoldimethacrylate as a crosslinking agent, in the presence of galactose as a template molecule with acrylamide as a functional monomer. After the synthesis of polymer, galactose was removed by methanol:acetic acid washing. The selectivity of galactose imprinted polymer for other saccharides was utilized by batch rebinding assay. The arrangement of functional groups within cavities versus shape selectivity is discussed. The results showed that, the orientation of the functional groups was the dominating factor for the selectivity of galactose imprinted polymer. The dissociation constants of polymer were determined by Scatchard analysis.     

胆酸印迹聚合物的制备及在含水介质中的结合性能

为了在含水介质中进行有效印迹,本研究中以双甲基丙烯酰-β-环糊精（BMA-β-CD）和2-(二乙基胺基)乙基甲基丙烯酸酯(DEAEM)为功能单体制备了胆酸印迹聚合物MIP1,并用平衡结合实验研究了MIP1在含水介质中对模板分子的识别能力。结果表明,MIP1比单独以BMA-β-CD或DEAEM为功能单体制备的印迹聚合物MIP2和MIP3,显示出对模板分子更好的选择性结合能力。MIP1的特异性吸附量ΔCP为38.81μmol/g,印迹因子IF为2.46。研究表明,在含水介质中,利用模板分子与功能单体之间的疏水作用和离子作用是提高印迹聚合物分子识别能力的关键。研究还表明,在识别过程中,疏水作用在驱动分子进入印迹孔穴时起重要作用。     

Synthesis of thermo‐responsive bovine hemoglobin imprinted nanoparticles by combining ionic liquid immobilization with aqueous precipitation polymerization

Surface molecular imprinting over functionalized nanoparticles has proved to be an effective approach for construction of artificial nanomaterials for protein recognition. Herein, we report a strategy for synthesis of core–shell protein‐imprinted nanoparticles by the functionalization of nano‐cores with ionic liquids followed by aqueous precipitation polymerization to build thermo‐responsive imprinted polymer nano‐shells. The immobilized ionic liquids can form multiple interactions with the protein template. The polymerization process can produce thermo‐reversible physical crosslinks, which are advantageous to enhancing imprinting and facilitating template removal. With bovine hemoglobin as a model template, the imprinted nanoparticles showed temperature‐sensitivity in both dispersion behaviors and rebinding capacities. Compared with the ionic‐liquid‐modified core nanoparticles, the imprinted particles exhibited greatly increased selectivity and two orders of magnitude higher binding affinity for the template protein. The imprinted nanoparticles achieved relatively high imprinting factor up to 5.0 and specific rebinding capacity of 67.7 mg/g, respectively. These nanoparticles also demonstrated rapid rebinding kinetics and good reproducibility after five cycles of adsorption–regeneration. Therefore, the presented approach may be viable for the fabrication of high‐performance protein‐imprinted nanoparticles with temperature sensitivity.     

蛋白质分子印迹聚合物研究

分子识别现象在生命过程中扮演着极其重要的角色,对此进行研究和探索是化学和生物学领域的核心课题,制备具有分子识别能力的人工受体是对该领域科学工作者的一个持久挑战．为此,相关研究人员进行了多方努力,创造性地发展了许多崭新的方法和手段,其中的分子印迹聚合物制备技术就是这些方法和手段中的一种.     

光接枝表面修饰法制备牛血红蛋白的分子印迹微球

聚苯乙烯球载体表面经引发转移终止剂修饰后, 采用光接枝表面印迹方法制备了以牛血红蛋白(BHb)为模板分子、丙烯酰胺为功能单体和N,N′-亚甲基双丙烯酰胺为交联剂的分子印迹聚合物微球(MIP). 进一步采用红外光谱(IR)、扫描电子显微镜(SEM)和元素分析对聚合物微球进行了表征, 证实了载体表面成功地接枝了分子印迹层, 并研究了其吸附性能和分子识别选择性能. 结果表明, 采用光接枝表面修饰法制备的分子印迹微球对模板分子有着很好的吸附容量和识别选择性.     

Optimization of Functional Monomer Content in Protein‐Imprinted Polymers

Abstract

We have prepared synthetic materials having binding specificity toward lysozyme using molecular imprinting. The lysozyme‐imprinted polymers were prepared on silica beads using acrylic acid, acrylamide, and N,N′‐methylenebisacrylamide. The molar ratio of acrylic acid to the template affected the selectivity and the maximum binding specificity was yielded with the molar ratio of 5 to 1 (acrylic acid/template). No binding specificity toward lysozyme was observed when there was no acrylic acid, and the binding specificity decreased when the amount of acrylic acid was high. The functional monomer‐template ratio indicated in this study could be useful for improving the binding specificity in molecular imprinting of proteins.     

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.