Dopamine selective molecularly imprinted polymers via post-imprinting modification

A novel synthetic dopamine receptor bearing bidentate binding sites were prepared by covalent imprinting using a disulfide linkage which is cleaved and oxidized to a non-covalent sulfoxide recognition group. The used templates have dopamine-like structures connected to an allyl moiety via a disulfide and to a 4-vinylphenyl group via a cyclic boronic diester. After the polymerization, the ester bonds were hydrolyzed and the disulfide bond was reduced to remove the template moiety from the polymer matrix, followed by the oxidation to transform the thiol residues into sulfonic acid (post imprinted process). The imprinted polymer adsorbed dopamine selectively in aqueous solution with the two-point interaction, i.e. the formation of cyclic boronic diester and electrostatic interaction with the sulfonic acid residue.     

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.     

Synthesis and Molecular Recognition of Molecularly Imprinted Polymer with Ibuprofen as Template

Ibuprofen and ketoprofen are chemically similar non‐steroidal anti‐inflammatory drugs widely used in the treatment of arthritis. Using a molecular imprinting technique, a simple and rapid method was developed for the simultaneous separation and determination of ibuprofen and ketoprofen. Molecular imprinting introduces artificial binding sites into a synthetic polymer matrix, allowing it to exhibit selective rebinding of template molecules. Imprinted polymers can be regarded as an HPLC stationary phase, important for pharmaceutical analysis. Most molecularly imprinted polymers (MIPs) are synthesized by free radical polymerization of functional monomers, resulting in an excess of crosslinking monomers. In this study, MIPs have been prepared with a ibuprofen template, which can form intramolecular hydrogen bonds. Methacrylic acid (MAA) and ethyleneglycol dimethacrylate (EGDMA) were used as the functional monomer and cross‐linker, respectively. Bulk polymerization was carried out at 4 °C under UV radiation. The resulting MIP was ground into 25?44 μm particles, which were slurry‐packed into analytical columns. Template molecules were removed by methanol‐acetic acid (9:1, v/v). We evaluated the template binding performance of the MIP using HPLC, with ultraviolet (UV) detection at 234 nm. Chromatographic resolution of ibuprofen and ketoprofen on the MIPs were appraised using buffer/acetonitrile (45/55, v/v) as the mobile phase. Results show that the MIPs prepared using ibuprofen as the template had a significant molecular imprinting effect. The method was successfully applied to the separation and analysis of ibuprofen and ketoprofen in pharmaceuticals.     

Semi‐Covalent Surface Molecular Imprinting of Polymers by One‐Stage Mini‐emulsion Polymerization: Glucopyranoside as a Model Analyte

This paper describes a new type of surface imprinting technique that combines the advantages of both the semi‐covalent approach and one‐stage miniemulsion polymerization. This process has been successfully applied for the preparation of glucose surface‐imprinted nanoparticles. The selective artificial receptors for glucopyranoside were fully characterized by IR, TEM and BET analyses, and their molecular recognition abilities by binding experiments carried out in batch processes. The molecular affinity and selectivity of the glucose molecularly imprinted polymers were accurately quantified. These characteristics are essential for verification of the efficiency of the developed surface imprinting process. The imprinting effect was clearly demonstrated using the batch rebinding method. We have found that the glucose imprinted polymers produced using the optimized one‐stage mini‐emulsion exhibited quite fast kinetics of binding and equilibration with glucopyranoside templates, compared to polymers prepared by bulk polymerization technique, as well as extremely low levels of unspecific bindings. We also demonstrated that glucose molecular imprinted polymer (MIP) exhibited very good selectivity for its original template compared to other glycopyranoside derivatives, such as galactose. Finally, the extraction of the binding properties from isotherms of binding by fitting to the bi‐Langmuir and Freundlich models allowed the determination of the affinity constant distribution of the binding sites. This imprinting protocol allowed the determination of an affinity constant (K_D), involving exclusively H‐bonding interactions, for the glucose MIP ( P2C ) with the best template 1 , in CH₃CN as the solvent system.

     

Preparation and application of hollow molecularly imprinted polymers with a super‐high selectivity to the template protein

Protein‐imprinted polymers with hollow cores that have a super‐high imprinting factor were prepared by etching the core of the surface‐imprinted polymers that used silica particles as the support. Lysozyme as template was modified onto the surface of silica particles by a covalent method, and after polymerization and the removal of template molecules, channels through the polymer layer were formed, which allowed a single‐protein molecule to come into the hollow core and attach to the binding sites inside the polymer layer. The adsorption experiments demonstrated that the hollow imprinted polymers had an extremely high binding capacity and selectivity, and thus a super‐high imprinting factor was obtained. The as‐prepared imprinted polymers were used to separate the template lysozyme from egg white successfully, indicating its high selectivity and potential application in the field of separation of protein from real samples.     

Preparation and characterisation of core-shell CNTs@MIPs nanocomposites and selective removal of estrone from water samples

This paper reports the preparation of carbon nanotubes (CNTs) functionalized with molecularly imprinted polymers (MIPs) for advanced removal of estrone. CNTs@Est-MIPs nanocomposites with a well-defined core-shell structure were obtained using a semi-covalent imprinting strategy, which employed a thermally reversible covalent bond at the surface of silica-coated CNTs for a large-scale production. The morphology and structure of the products were characterised by transmission electron microscopy and Fourier transform infrared spectroscopy. The adsorption properties were demonstrated by equilibrium rebinding experiments and Scatchard analysis. The results demonstrate that the imprinted nanocomposites possess favourable selectivity, high capacity and fast kinetics for template molecule uptake, yielding an adsorption capacity of 113.5 μmol/g. The synthetic process is quite simple, and the different batches of synthesized CNTs@Est-MIPs nanocomposites showed good reproducibility in template binding. The feasibility of removing estrogenic compounds from environmental water using the CNTs@Est-MIPs nanocomposites was demonstrated using water samples spiked with estrone.     

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.     

Preparation and characterization of molecularly imprinted organic–inorganic hybrid materials by sol–gel processing for selective recognition of ibuprofen

This work adopted semi-covalent imprinting to prepare molecularly imprinted polymers (MIP) with ibuprofen, a non-steroidal anti-inflammatory drug, as template by sol–gel processing, which is characterized by both the high affinity of covalent binding and the mild operation conditions of non-covalent rebinding. A functional monomer, which was used to synthesize the monomer-imprinted molecule complex, was prepared by multi-step synthesis for the first time. MIP was characterized by Fourier transform IR spectrum and nitrogen adsorption. Thin-layer chromatography separation was used to evaluate the specific molecular recognition ability of MIP. In addition, dynamic and thermodynamic studies on MIP imprinting ibuprofen were undertaken. The results of equilibrium rebinding experiments showed that MIP exhibited good adsorption capacity for ibuprofen. Scatchard analysis illustrated that the template-polymer system shows only one-site binding behavior with a dissociation constant of 1.84 mmol L^?1. Dynamic adsorption exhibited pseudo-second-order kinetics. The positive value of ΔH^θ and the negative values of ΔG^θ demonstrated that the binding system for MIP is endothermic and spontaneous.     

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.     

A Molecularly Imprinted Nicotine-Selective Polymer

Abstract

A (-)-nicotine-selective polymer was prepared by molecular imprinting technique using methacrylic acid as a functional monomer. Liquid-chromatographic tests, using the polymers as a stationary phase, exhibited that the basicity of the functional group of (-)-nicotine is crucial for rebinding by the molecularly imprinted polymer. Scatchard analysis implied that the binding sites generated within the polymer are heterogeneous in terms of affinity, and the apparent dissociation constant of the highest affinity binding sites was estimated as 3.7 μM.     

基于银增强金标记物的阳极溶出伏安免疫分析用于补体第三成分的测定

分子印迹是制备对特定分子具有专一性结合能力的聚合物的技术,所制备的聚合物被称为分子印迹聚合物（Molecularly imprinted polymers,MIPs）,此类聚合物在分离提纯、模拟酶和传感器等方面均显示出广阔的应用前景,迄今,小分子化合物的印迹技术已经十分成熟。     

表面分子印迹聚合物纳米线用于蛋白质的特异性识别

手性配体交换色谱是拆分手性化合物,特别是氨基酸和羟基酸对映体的一种有效方法,通常以光活性氨基酸或其衍生物为手性选择子,可通过键合及涂渍制备手性固定相,也可作为流动相添加剂来实现手性配体交换色谱分离分析,配体交换键合固定相需要完成载体和手性选择子之间的偶联,键合量因受到载体和制备条件的影响而较难控制,且柱效较低。     

The electrochemical characterisation of benzyl mercaptan-modified Au(111): structure and copper deposition

The behaviour of benzyl mercaptan self-assembled monolayers on Au(111) in sulfuric acid solution was studied using cyclic voltammetry and in situ scanning tunnelling microscopy. Modification of the Au(111) surface in an ethanolic solution of benzyl mercaptan leads to a disordered monolayer. However, by partial reductive desorption a striped c (15 x sqrt [3]) and a (2 x sqrt [3]) structure were obtained. The disordered benzyl mercaptan film was also used for the study of copper deposition. At -0.02 V versus SCE, that is in the underpotential deposition region, monoatomic high islands appear on the surface. Bulk deposition of copper starts at -0.08 V versus SCE with the growth of dendrites underneath the thiol film. At higher overpotentials, the growth of three-dimensional copper clusters commences.     

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。     

基于多重动态共价键的环氧类玻璃网络的制备与性能

以三羟甲基丙烷三缩水甘油醚(TTE)为基体, 2,2′-(1,4-亚苯基)-双[4-硫醇1,3,2-二氧杂戊烷](BDB)和3,3-二硫代二丙酸(DTDPA)为交联剂, 通过环氧-巯基“点击”反应和环氧-羧酸酯化反应, 制备了基于多重动态共价键(硼酸酯键、 二硫键和酯键)的环氧类玻璃网络. 利用红外光谱和拉曼光谱对其结构进行了表征, 结果表明, 环氧类玻璃中不仅存在硼酸酯键、 二硫键和酯键, 还存在可逆氢键, 并且大量氢键的存在能提高环氧类玻璃的交联度. 对所得环氧网络的热稳定性、 热机械性能和力学性能进行了测试, 并对基于多重动态共价键环氧网络进行了自修复、 焊接、 形状记忆和再加工能力测试. 结果表明, 在80 ℃下可实现网络的完全自修复、 再加工与焊接, 且焊接后样品的力学性能(拉伸强度)恢复率在80%以上, 具有优异的功能性.     

Affinity screening by packed capillary high performance liquid chromatography using molecular imprinted sorbents. II. Covalent imprinted polymers

This study concentrates on the production of covalent molecular imprint polymers (MIPs) as highly selective sorbents for nortriptyline (NOR), a representative tricyclic antidepressant (TCA). The functionalized template contains a polymerizable 4-vinylphenyl carbamate moiety used to bind the template molecule to the polymer matrix. Polymerization with a cross-linker followed by hydrolytic cleavage of the labile carbamate functionality leaves an MIP with selective binding sites capable of binding template through hydrogen bonding interactions. Demonstrated chromatographically through a "selection index", these MIPs showed high selectivity for the template molecule (NOR) among a library of structurally similar compounds. The recognition was found to correlate with structural similarity to the template compound. A direct comparison between covalent and non-covalent molecular imprinting strategies reveals a great deal of improvement in the peak shape of the retained compound resulting from covalent imprinting (evidenced by peak asymmetry factors A.).     

Chromatographic characterization of molecularly imprinted polymers

Recent efforts in the investigation of chromatographic characterization of molecularly imprinted polymers (MIPs) have focused mainly on the nature of heterogeneous binding sites. More data on the thermodynamics than on the kinetic features of MIP columns have been published. The present article addresses the sources of peak broadening and tailing, which are the main drawbacks often associated with imprinted polymers in chromatography for practical applications. With use of the theory of nonlinear chromatography, the peak properties of a MIP column, including the retention and peak broadening and tailing, can be well interpreted. Efforts to improve chromatographic efficiency using MIPs prepared by approaches different from the conventional method, including covalent imprinting and the format of uniformly sized spherical microbeads, are reviewed and discussed. This review leads to the conclusion that nonlinear chromatography theory is useful for characterizing chromatographic features of MIP columns, since a MIP is essentially an affinity-based chromatographic stationary phase. We expect more theoretical and experimental studies on the kinetic aspects of MIP columns, especially the factors influencing the apparent rate constant, as well as the analysis of the influences of mobile-phase composition on the chromatographic performance. In addition to revealing the affinity interaction by molecular recognition, slow nonspecific interactions which may be inherited from the imperfect imprinting and may be involved in the rebinding of the template to MIPs also need to be characterized. Figure The peak broadening and tailing associated often with molecularly imprinted polymers (MIPs) in column chromatography for practical applications can be well characterized by the theory of nonlinear chromatography.     

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.     

Sulfur-containing polymers. IV. Preparation and properties of poly(sulfenyl thiocarbonates)

Poly(sulfenyl thiocarbonates) have been prepared for the first time by the stepwise condensation of chlorocarbonylsulfenyl chloride with diols and dithiols. The polymers were obtained in high yield. Generally they were crystalline solids and were soluble in chlorinated hydrocarbons. On treatment with benzyl mercaptan in the presence of triethylamine, the polymers afforded a diol, carbonyl sulfide, and a disulfide compound. This reaction was extended to the preparation of alternating copolydisulfides.     

Post-oxidative conversion of thiol residue to sulfonic acid in the binding sites of molecularly imprinted polymers: disulfide based covalent molecular imprinting for basic compounds

An imprinted polymer using a disulfide derivative as a template was treated with NaBH4 to yield the polymer with thiol groups in the binding sites. The thiol groups were then oxidized with H2O2/AcOH to yield the molecularly imprinted polymer with sulfo groups in the binding sites. This site conversion can provide amine-imprinted polymers, in which amine is retained to the imprinted polymer by the strong electrostatic interaction between the amino group and the sulfo group in the binding sites.