Novel polymer system for molecular imprinting polymer against amino acid derivatives

Molecular imprinting polymers (MIPs) against N-Cbz-L-Tyr were prepared utilizing different polymer systems and evaluated in HPLC mode. It was found that MEP utilizing cocktail functional monomers, acrylamide 2-vinylpyridine showed better molecular recognition and better separation ability for the template molecule than those utilizing other functional monomers. MIP utilizing trimethylolpropane trimethacrylate as cross-linker showed higher load capacity and separation factor than those utilizing ethylene glycol dimethacrylate as cross-linker. Increasing the concentration of competing solvent, acetic acid weakened the ionic interaction and hydrogen bonding between the analyte and the functional monomers, 2-vinylpyridine and acrylamide, when the template enantiomer was separated by HPLC. Therefore increasing of the concentration of acetic acid leads to decreasing of capacity factor, separation factor and resolution.     

A comparative study of the potential of acrylic and sol-gel polymers for molecular imprinting

The successful molecular imprinting of 2-aminopyridine (2-apy) in bulk polymerisations of acrylic and sol-gel based polymers has been achieved. Both polymeric systems reveal varying degrees of affinity in rebinding the original template as well as a number of structural analogues. Rebinding was conducted in chloroform, acetonitrile and methanol in order to assess the role of hydrogen bonding in imprinting. The acrylic imprinted polymer retained approximately 50% of the template in rebinding studies in chloroform compared to 100% for the sol-gel. However, this higher affinity for the sol-gel was accompanied by a higher degree of non-specific binding. While the acrylic polymer performed poorly in acetonitrile, the sol-gel maintained a high degree of discrimination.The acrylic polymer exhibited little discrimination between imprinted and reference polymers for 3-aminopyridine (3-apy) indicating the high selectivity of the MIP polymer for 2-apy relative to 3-apy. This selectivity was reduced in acetonitrile. Selectivity of the sol-gel for 2-apy in chloroform was poor as 3-apy was retained to a similar degree. Comparable results were obtained in acetonitrile. 4-Aminopyridine (4-apy) bound strongly to all polymers in all solvents and proved very difficult to remove due to the high degree of non-specific binding for both polymeric matrices.     

绿色分子印迹技术简论

解析了绿色分子印迹技术(GMIT)的概念;结合水相和其他新型分子印迹技术、聚合物辅助设计及新型原材料的发展,简要阐述GMIT的发展动向.指出在绿色化学日益深入人心的今天,有必要深入探索和发展绿色分子印迹技术,从而拓展分子印迹技术研究领域、促进绿色化学的发展.     

苯丙氨酸衍生物分子印迹聚合物的制备及手性拆分研究

以分子印迹技术合成分子印迹聚合物，作为手性色谱柱的固定相来拆分苯丙氨酸衍生物的对映异构体。采用了新型的交联剂及光引发剂。模板分子和可聚合的功能单体形成配合物是分子印迹聚合物必不可少的条件。模板分子与功能单体的比例为1:4时，获得了良好的分离效果，分离因子α为1.69。光聚合方式合成的分子印迹聚合物比热聚合方式合成的拆分能力要高。且聚合的温度越低，聚合物分离效果越好。     

基于分子印迹技术的牛血清白蛋白电位式传感器的研究

以牛血清白蛋白(BSA)为模板,合成了分子印迹聚合物凝胶(MIP),进而制得了以聚氯乙烯(PVC)为支撑膜的BSA电位式传感器。采用直接电位法测得BSA在浓度0.1～1.0 mg/mL范围内与电位呈线性关系。此电极制作简单,可用于BSA的测定。     

分子印迹技术研究进展

分子印迹技术是制备对特定目标分子具有特异性识别能力的高分子材料的技术,所制备的高分子材料被称为分子印迹聚合物.分子印迹聚合物因具有预定性、识别性和实用性三大优点已广泛应用于分离、模拟抗体与受体、催化剂以及仿生传感器等方面和领域,显示出了广泛的应用前景.作者对分子印迹技术的发展历史、基本原理、分类、应用现状以及一些新的研究热点进行了综述.     

Fluorescent sensing of homocysteine by molecular imprinting

The feasibility of biomimetic molecular sensing of homocysteine, an independent risk factor for cardiovascular diseases, was studied. The sensing approach coupled fluorescent derivatization of dl-homocysteine by a thiol-specific fluoro-tagging agent, N-(1-pyrenyl)maleimide, with molecular recognition by a molecularly imprinted polymer (MIP) matrix. The non-covalent MIP was fabricated using the N-(1-pyrenyl)maleimide-dl-homocysteine (PM-H) adduct as template. The PM-H-MIP was found to possess outstanding analyte-specific affinity for PM-H with binding constant, K_B, of 9.28±1.6×10⁵ M⁻¹ and density of recognition sites, B_max, of 11.9±0.8 nmol/g dried MIP. Following in situ fluorescent derivatization, luminescent response of the MIP was found to correlate linearly with concentration of dl-homocysteine in the range corresponding to realistic total homocysteine concentration in blood plasma. Besides being a passive recognition matrix for the binding of the fluoro-tagged analyte, the PM-H-MIP material was found to be able to specifically enhance the rate of derivatization reaction between dl-homocysteine and N-(1-pyrenyl)maleimide. In a sense, the MIP transformed a fluoro-tagging agent, which is generally reactive towards a broad spectrum of thiol-containing species, into a dl-homocysteine-specific derivatizing agent. The mechanism of such analyte-specific enhancement of derivatization rate and its advantages to the biomimetic molecular sensing are discussed.     

Enantioselective polymer prepared by surface imprinting technique using a bifunctional molecule

An enatioselective surface-imprinted polymer for an amino acid derivative (N-benzyloxycarbonyl-glutamic acid, Z-Glu) was prepared using the bifunctional molecule, benzyldimethyl-n-tetradecylammonium chloride (Zeph). The long-chain quaternary ammonium chloride was found to serve the dual function of an emulsifier and host molecule, while conventional functional molecules possess only the latter function. Chiral recognition ability and ligand specificity of the imprinted polymer were demonstrated by several batchwise tests using different four amino acid derivatives. The surface-imprinted polymer could recognize the chirality of N-protected glutamic acid; therefore, it preferentially adsorbed the corresponding enantiomer that was imprinted in the preparation. The pH and buffer concentration in the aqueous solution are the key factors enhancing enantioselectivity. The molecularly imprinted polymer could distinguish the specific structure from other molecular analogues, even though the structural difference was the only methylene group. The high interfacial activity of the functional molecule and the low swelling property of the imprinted polymer were important in ensuring high imprinting effect. The mechanism of chiral recognition on the polymer was also discussed.     

A novel α-fetoprotein-MIP immunosensor based on AuNPs/PTh modified glass carbon electrode

A new alpha-fetoprotein-MIP (AFP-MIP) immunosensor based on glass carbon electrode (GCE) modified with polythionine (PTh) and gold nanoparticles (AuNPs) was successfully prepared for the sensitive detection of AFP. The AFP-MIP immunosensor presented a facile preparation, low sample consumption, and good stability, and could become a new promising method for the detection of AFP.     

Preparation of a PTE simulacrum based on surface molecular imprinting

Firstly,we synthesized N-methacryloyl-histidine monomer and N-methacryloyl-histidine-Cu²⁺ complex(MAH-Cu²⁺).Then the molecular imprinting polymers（MIP） has been prepared by surface grafting on uniform polystyrene（PS） core using reversible addition-fragmentation transfer polymerization（RAFT） with MAH-Cu²⁺ as the functional monomer,methyl paraoxon as the template to simulate phosphodiesterase（PTE）.Finally,we have investigated the catalytic hydrolytic activities of MIP and non-imprinting polymers（NIP） to the template methyl paraoxon and the template analogue ethyl paraoxon respectively by UV spectrophotometry.The results showed that the catalytic hydrolytic activity of MIP to the template methyl paraoxon was highest and the value of k is 8.67×10^-5 mmol L^-1 min^-1,3.89-fold higher than MIP to the template analogue ethyl paraoxon,2.79-fold higher than NIP to the template methyl paraoxon.The K_M,r_m of MSP are also determined,and K_M = 3.95×10^-4mol/L,r_m = 2.12μmol/ min.The MIP can be reused with only lose 7%of catalytic activity for four cycles.     

Molecular imprinting of β-cyclodextrin/cholesterol template into a silica polymer for cholesterol separation

The molecular assembly formed by the inclusion complex of cholesterol in β-cyclodextrin (β-CD:chol) was used as a template for the molecular imprinting of a sol–gel polymer (MIP/β-CD:chol), produced with tetraethoxysilane (TEOS) as precursor. The MIP/β-CD:chol and pure silica matrix (PSM) were tested for the efficiency of cholesterol removal from solutions at different cholesterol concentrations (1–10 mg/mL). The adsorption tests were run at 25°C using 1% (w/v) solid/liquid suspensions during 24 h. The MIP/β-CD:chol data on cholesterol adsorption was fitted by the Langmüir isotherm model, giving a maximum adsorption capacity of 76.5 mg cholesterol/g-adsorbent. The PSM data did conform to the Langmüir model. The maximum cholesterol adsorption achieved with the PSM was higher, 251 mg/g, probably due to multilayer adsorption. The hydrophobic silica matrix, imprinted with the inclusion complex of β-CD and a target molecule, has the potential of being used as an adsorbent for other organic molecules.     

Synthesis and properties of molecular imprints of darifenacin: The potential of molecular imprinting for bioanalysis

Summary A molecularly imprinted polymer has been developed which subsequently demonstrated an ability to selectively retain darifenacin (UK-88, 525-S) from aqueous acetonitrile when used as a stationary phase in HPLC columns and as a packing in solid-phase extraction cartridges. The imprinted polymer is applicable to a wide range of analytical methods including extraction from plasma, purification of radiolabelled UK-88,525, chiral separations and separation of metabolites and structural analogues. The polymer is able to extract darifenacin directly from a protein-precipitated human plasma/acetonitrile (1:1 v/v) mixture with 100% recovery. The imprinted polymer can also effect a repurification of¹⁴C-labelled darifenacin. The drawbacks of molecular imprints for ultra-trace bioanalysis (in the sub-nanogram/mL range) are discussed. These centre on the difficulty of removing all the template from the polymer and the consequent effects of template bleed on assay precision and accuracy when used as solid-phase extraction cartridges. Possible solutions to this problem are considered. Presented at: Affinity Chromatography Conference, Cambridge, UK, July 1–3, 1997.     

Application of a novel electrosynthesized polydopamine-imprinted film to the capacitive sensing of nicotine

The application of novel electrosynthesized polydopamine (PDA)-imprinted film as a recognition element for the capacitive sensing of nicotine is reported. The PDA-imprinted film was electropolymerized directly on the gold electrode surface in the presence of nicotine without an additional self-assembled thiol sublayer. The compact PDA film has various functional groups that aid the imprinting procedure. Furthermore, the film shows good capacitive response since it is insulating in nature and ultrathin. The sensor’s linear response range for nicotine was between 1–25 μmol L⁻¹, with a detection limit of 0.5 μmol L⁻¹. The proposed molecularly imprinted polymer capacitive (MIPC) sensor exhibited good selectivity for nicotine. The reproducibility and repeatability of the MIPC senor were all found to be satisfactory. The results from sample analysis confirmed the applicability of the MIPC sensor to quantitative analysis.     

A novel electromagnetism‐assisted imprinting technology to replicate microstructures onto a large‐area curved surface using a flexible magnetic mold

Replication of microstructures from a mold onto a curved surface is difficult. The conformal contact between the mold and the substrate has to be ensured. The present study proposes an innovative mechanism, which employs an electromagnetic disk to provide magnetic force and a PDMS flexible mold with a layer compounded magnetic powder. This mechanism provides not only the gradual contact from center to edge to avoid air entrapment but also conformal contact between the mold and the substrate during the imprinting operation. A system based on this electromagnetic soft imprinting technology has been implemented, and imprinting to replicate microstructures from the mold onto a curved surface has been carried out. The results reveal that the PDMS magnetic mold and the electromagnetic disk‐controlled magnetic force can successfully perform the imprinting and accurately replicate the microstructures onto the large‐area, curved surface glass. The PDMS flexible magnetic mold incorporated with the magnetic disk can be employed to achieve the conformal contact between the mold and the substrate. In addition, due to the low surface free energy of the PDMS, the de‐molding without sticking can be easily accomplished. Copyright © 2008 John Wiley & Sons, Ltd.     

Ultrasensitively sensing acephate using molecular imprinting techniques on a surface plasmon resonance sensor

An ultrathin molecularly imprinted polymer film was anchored on an Au surface for fabricating a surface plasmon resonance sensor sensitive to acephate by a surface-bound photo-radical initiator. The polymerization in the presence of acephate resulted in a molecular-imprinted matrix for the enhanced binding of acephate. Analysis of the SPR wavenumber changes in the presence of different concentrations of acephate gave a calibration curve that included the ultrasensitive detection of acephate by the imprinted sites in the composite, K_ass for the association of acephate to the imprinted sites, 7.7 × 10¹² M⁻¹. The imprinted ultrathin film revealed impressive selectivity. The selectivity efficiencies for acephate and other structurally related analogues were 1.0 and 0.11-0.37, respectively. Based on a signal to noise ratio of 3, the detection limits were 1.14 × 10⁻¹³ M for apple sample and 4.29 × 10⁻¹⁴ M for cole sample. The method showed good recoveries and precision for the apple and cole samples spiked with acephate solution. This suggests that a combination of SPR sensing with MIP film is a promising alternative method for the detection of organophosphate compounds.     

分子印迹技术在蛋白质分离分析中的研究进展

蛋白质结构复杂,种类多样,与各种生命活动密切相关。大部分蛋白质在生物体中含量极低,对其分析检测带来极大困难。因此实现复杂生物样品中蛋白质的选择性识别与分离,对实现蛋白质的分离分析意义重大。通过分子印迹技术制备的分子印迹聚合物含有与模板分子大小、形状一致,官能团相互匹配的三维印迹空穴,在蛋白质的选择性识别与分离领域显示出了巨大的发展潜力。但是,由于蛋白质具有尺寸较大、构型易变、结构复杂等特点,分子印迹技术在蛋白质印迹中面临着巨大挑战。该文在介绍几种新型分子印迹技术包括表面印迹、抗原决定基印迹和金属螯合物印迹的基础上,综述了近3年分子印迹技术在蛋白质分离分析方面的应用,并对其发展进行了总结与展望。     

A novel method to determine the molecular weight of the oligomers of biodegradable polymer

The biodegradable polymers used in controlled release applications are primarily insoluble polymers which undergo chemical or enzymatic hydrolysis to form soluble monomeric or oligomeric units. To determine the endurance of the polymer after implantation or injection into the body it is important to determine the rate of elimination of the intermediates formed upon the hydrolysis of the polymer. It is essential to identify these intermediates before its elimination rate can be determined. Identification of these intermediates is a problem because they are difficult to isolate, and are thermally and hydrolytically unstable. A new technique is proposed, taking advantage of the neighboring group effect on the hydrolysis of ionic and non-ionic oligomers, to determine the molecular weight of unknown species that are formed upon hydrolysis of the polymer. The technique involves the determination of the specific acid and base catalytic rate constants. To demonstrate the technique, a time sequence synthesis was carried out to synthesize several oligomers that would be forming upon the hydrolysis of poly(butylene tartrate). Hydrolysis studies were conducted with these oligomers and the samples were analyzed by liquid chromtography. The observed rate constant for the hydrolysis under acidic and alkaline pH medium were calculated from the terminal slopes of the first order plot. The observed rate constants were further utilized to calculate the specific acid and base catalytic rate constants. These specific rate constants, along with the micro-hydrogen and -hydroxyl ion catalytic rate constants, were used to determine the molecular weight of the intermediate species. The molecular weight obtained from the kinetic parameters was in excellent agreement with the results obtained from fast atom bombardment mass spectrometry. The same type of analysis can be extended to any multifunctional group compound which has repeat units and can undergo a specific reaction which can be accurately measured.     

基于分子印迹电聚合膜的褪黑素传感器的研究

在弱酸条件下,以邻苯二胺为功能单体,褪黑素为模板,以电化学聚合物法在铂电极表面合成了性能稳定的褪黑素分子印迹聚合物膜.采用循环伏安法(CV)和差分脉冲法(DPV)对分子印迹传感器的识别性能进行了研究.结果表明:此传感器对褪黑素具有快的响应、良好的选择性和高的灵敏度.以K3Fe(CN)6为电子传递媒介,建立了一种差分脉冲伏安法(DPV)间接检测褪黑素的分析方法.在1×10-10～1×10-8 moL/L范围内,褪黑素的浓度与K3Fe(CN)6的相对峰电流变化呈良好的线性关系;检出限为1×10-11 mol/L(S/N=3).将此传感器应用于复合褪黑素及尿样中褪黑素含量的测定,加标平均回收率大于94％.     

分子印迹技术在蛋白质识别中的应用进展

分子印迹技术是一种制备具有分子识别能力的聚合物的有效技术,已经广泛应用于制备对小分子具有选择性的分子印迹聚合物,但制备能够特异性识别生物大分子--蛋白质的分子印迹聚合物的研究仍然具有挑战性。本文讨论了制备蛋白质分子印迹聚合物的难点,评述了目前印迹蛋白质的方法及各自的优缺点,展望了蛋白质印迹技术的发展趋势。     

Novel enrofloxacin imprinted polymer applied to the solid-phase extraction of fluorinated quinolones from urine and tissue samples

A new molecularly imprinted polymer, prepared following a non-covalent approach, was synthesised using enrofloxacin as a template molecule. The imprinting effect of the polymer was verified by chromatographic evaluation and, interestingly, this evaluation also revealed that the imprinted polymer showed a high degree of cross-reactivity for ciprofloxacin, the major metabolite of enrofloxacin. The molecularly imprinted polymer was then applied as a selective sorbent in a two-step solid-phase extraction method focussing upon complex biological matrices, specifically human urine and pig liver. This two-step solid-phase extraction protocol, in which a commercial Oasis HLB cartridge and a molecularly imprinted solid-phase extraction cartridge were combined, allowed enrofloxacin and ciprofloxacin to be determined by liquid chromatography coupled to a UV detector at levels below the maximum residue limits established by the European Union. The quantification and detection limits in tissue samples of enrofloxacin and ciprofloxacin were established at 50 μg kg⁻¹ and 30 μg kg⁻¹, respectively.