Selective recognition of ovalbumin using a molecularly imprinted polymer

Micro-contact imprinting has been used to form thin-film molecular imprints of ovalbumin (OVA) in polymers supported on glass slides. Thermocalorimetric data was used to optimise the choice of functional monomer and cross-linker to maximise selectivity and minimise non-specific recognition.A polymer comprising polyethyleneglycol 400 dimethacrylate (95 vol.%) and methacrylic acid (5 vol.%) showed both maximum recognition for OVA when made as a molecularly imprinted polymer (MIP), and minimal recognition when made as a non-imprinted, i.e. control polymer. OVA rebinding to the molecularly imprinted polymer, from a buffered 2 µM OVA solution, was 1.55 × 10^{− 11} mol cm^{− 2}, while the control polymer showed 10-fold less re-binding, i.e. 0.154 × 10^{− 11} mol cm^{− 2}.Experiments in which human serum albumin (HSA), conalbumin, ovomucoid or lysozyme, were re-bound to the polymers, either as single proteins or in competition with OVA, showed them to have low affinity for the polymer formulation used. Of the competing proteins examined, in non-competitive binding experiments, HSA showed the greatest affinity 0.45 × 10^{− 11} mol cm^{− 2} for the OVA imprinted polymer. In two protein competition experiments, i.e. with OVA and a competing protein present at equal concentrations (2 µM), OVA binding to the OVA imprinted polymer was in all cases significantly greater than that of the competitor.     

Synthesis and binding properties of a noncovalent molecularly imprinted testosterone-specific polymer

In this study, molecular imprinting was used to develop a method based on noncovalent interactions for synthesis of a testosterone-specific polymer. The effect of the different template–monomer ratios, the particle sizes of polymers, and chromatographic mobile phases on steroid–polymer interactions are discussed. The polymer obtained was found to interact specifically with testosterone, while other steroids under study were eluted close to the void volume in the HPLC experiments. Batch rebinding studies in acetonitrile were undertaken to quantitatively evaluate the affinity of the polymer for testosterone. During this experiment, the testosterone concentration was measured in two ways: spectrophotometrically and by HPLC on a column with testosterone-specific imprinted polymer synthesized by us. Both methods resulted in similar values of association constants and the number of binding sites. However, the second method has obvious advantages when the analyzed solution contains a mixture of optically dense compounds. The results obtained focus on the two-point binding nature of the imprinted polymer–testosterone interaction and the significant role of hydrogen bonds between the OH group of testosterone and carboxy group of methacrylic acid residues inside specific recognition sites of the imprinted polymer. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1725–1732, 1998     

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。     

A new enzyme model for enantioselective esterases based on molecularly imprinted polymers

An efficient enzyme model exhibiting enantioselective esterase activity was prepared by using molecular imprinting techniques. The enantiomerically pure phosphonic monoesters 4 L and 5 L were synthesized as stable transition-state analogues. They were used as templates connected by stoichiometric noncovalent interactions to two equivalents of the amidinium binding site monomer 1. After polymerization and removal of the template, the polymers were efficient catalysts for the hydrolysis of certain nonactivated amino acid phenylesters (2 L, 2 D, 3 L, 3 D) depending on the template used. Imprinted catalyst IP4 (imprinted with 4 L) enhanced the hydrolysis of the corresponding substrate 2 L by a factor of 325 relative to that of a buffered solution. Relative to a control polymer containing the same functionalities, prepared without template 4 L, the enhancement was still about 80-fold, showing the highest imprinting effect up to now. In cross-selectivity experiments a strong substrate selectivity of higher than three was found despite small differences in the structure of the substrate and template. Plots of initial velocities of the hydrolysis versus substrate concentration showed typical Michaelis-Menten kinetics with saturation behavior. From these curves, the Michaelis constant K(M) and the catalytic constant k(cat) can be calculated. The enantioselectivity shown in these values is most interesting. The ratio of the catalytic efficiency k(cat)/K(M), between the hydrolysis of 2 L- and 2 D-substrate with IP4, is 1.65. This enantioselectivity derives from both selective binding of the substrate (K(M)L/K(M)D=0.82), and from selective formation of the transition state (k(cat)L/k(cat)D=1.36). Thus, these catalysts give good catalysis as well as high imprinting and substrate selectivity. Strong competitive inhibition is caused by the template used in imprinting. This behavior is also quite similar to the behavior of natural enzymes, for which these catalysts are good models.     

Optical interrogation of molecularly imprinted polymers and development of MIP sensors: a review

This article reviews the progress and developments achieved in the past five years (2000–2005) in the application of optical analytical techniques to the evaluation of molecularly imprinted polymer (MIP) characteristics. The MIP binding efficiency, recognition processes and selectivity have been intensively studied by optical means due to the general high sensitivity and simplicity of the utilisation of optical techniques. In addition, recent progress in the covalent linkage of MIPs to optical transducers has allowed for the realisation of highly efficient and robust optical MIP-based molecular recognition sensors. The review provides insight into the various approaches to the optical interrogation of MIPs, and is organised according to the type of optical technique employed (fluorescence, UV/Vis and infrared spectroscopy, surface plasmon resonance, chemiluminescence, refractive interference spectroscopy and Raman scattering) and the detailed strategies applied. The review also covers the recent progress achieved in the area of optical sensors based on MIPs.     

Discrimination of peptides by using a molecularly imprinted piezoelectric biosensor

Based on the direct formation of a molecularly imprinted polymer on gold electrodes, we have developed a peptide sensor for the detection of low-molecular-weight peptides. A new cross-linking monomer, (N-Acr-L-Cys-NHBn)(2), was employed to attach the surface of the chip and to copolymerize with other monomers. Interestingly, N-benzylacrylamide participates in the polymerization and recognition is carried out in an aqueous environment. By using quartz crystal microbalance detection, short peptides can be monitored by their interaction with plastic antibodies specific for the target peptides. The selectivity of molecularly imprinted polymers and the sensitivity of such artificial biosensors have been combined to differentiate between traces of oxytocin and vasopressin to the ng mL(-1) scale.     

Synthesis and characterization of hybrid molecularly imprinted polymer (MIP) membranes for removal of methylene blue (MB)

This work reports the synthesis and characterization of a hybrid molecularly imprinted polymer (MIP) membrane for removal of methylene blue (MB) in an aqueous environment. MB-MIP powders were hybridized into a polymer membrane (cellulose acetate (CA) and polysulfone (PSf)) after it was ground and sieved (using 90 μm sieve). MB-MIP membranes were prepared using a phase inversion process. The MB-MIP membranes were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Parameters investigated for the removal of MB by using membrane MB-MIP include pH, effect of time, concentration of MB, and selectivity studies. Maximum sorption of MB by PSf-MB-MIP membranes and CA-MB-MIP membranes occurred at pH 10 and pH 12, respectively. The kinetic study showed that the sorption of MB by MB-MIP membranes (PSf-MB-MIP and CA-MB-MIP) followed a pseudo-second-order-model and the MB sorption isotherm can be described by a Freundlich isotherm model.     

Synthesis and characterization of poly(methacrylic acid)‐based molecularly imprinted polymer nanoparticles for controlled release of trinitroglycerin

In this study, a novel molecularly imprinted polymer (MIP) based on methacrylic acid (MAA) monomer was synthesized to control release of trinitroglycerin (TNG) as a vasodilator drug for adjusting the cardiac conditions. For this purpose, TNG nanospheres based on poly(methacrylic acid) (PMAA) were prepared by using the precipitation polymerization process. The synthesized TNG nanospheres‐based MIP samples were characterized by means of Fourier transform infrared spectroscopy and field‐emission scanning electron microscopy in order to investigate their provided active functional groups within the cavities as well as morphology, respectively. The results showed that the appropriate non‐covalent bindings between the TNG (template) and PMAA provided within the MIP samples with imprinting factor of 1.98 were achieved by optimizing the amounts of trimethylolpropane trimethacrylate (TRIM) as a cross‐linker and MAA as a functional monomer. On the basis of these obtained conditions, the polymeric nanospheres containing TNG were formed in shape of spherical particles with an average diameter sizing about 40 nm. These remarkable results were obtained by the use of 1:10 molar ratio of TRIM/TNG and 1:6 molar ratio of MAA/TNG. Moreover, in‐vitro release of the TNG from the MIP samples to phosphate buffer solution (pH = 7.4) indicated that the MIP samples had a moderate and gradual release compared with the non‐imprinted polymer samples. These outcomes conducted us to consider the samples as carriers for adjusting potentially cardiac conditions. Copyright © 2016 John Wiley & Sons, Ltd.     

槲皮素表面分子印迹聚合物的制备及其应用研究

以接枝双键的凹凸棒土(TM)为载体,槲皮素为模板分子,采用表面印迹技术制备对槲皮素具有特异吸附性能的分子印迹聚合物(MIP)。利用光谱法选择实验条件及对化合物表征。采用静态法研究聚合物对槲皮素的结合性能与识别性能。结果表明,该分子印迹材料对槲皮素具有特异的识别特性和优良的亲和性,提高了传统聚合物的结合率。以该印迹聚合物为固相萃取材料,结合高效液相色谱法,对白菜中的槲皮素进行分离富集,方法回收率为84.0%~90.6%,相对标准偏差低于5.6%。     

Selectivity and recovery performance of phosphate-selective molecularly imprinted polymer

A phosphate-selective molecularly imprinted polymer was prepared using 1-allyl-2-thiourea as a functional monomer, and the binding ability and selectivity of the polymer were evaluated. The imprinted polymer showed high binding ability to and selectivity for phosphate in aqueous media. The recoverability of phosphate from the imprinted polymer was also examined, and nearly 70% of highly concentrated phosphate could be recovered.     

Study of structural parameters on the adsorption selectivity of a molecularly imprinted polymer

This work was focused on the influence of match degree of structure parameters i.e. molecular size, volume and polarity (denoted as R_d, V_d and P_d) between imprinted cavities in Qu-MIP and Xn on the adsorption selectivity. The results presented that the influence of R_d on the adsorption selectivity was the largest and the most regular, while the influence of P_d was the smallest and the most irregular. Besides, the influence degree of V_d was decreased in general with the increase of R_d. However, as R_d was in the threshold of [0.99, 1.02], V_d would rise to the major influence factor. Furthermore, utilizing data obtained from experiment, the influence authority of R_d, V_d and P_d on the adsorption selectivity was calculated theoretically through multiple linear regression and principal component analysis of IBM SPSS Statistics 20, and results showed the authority order was R_d, V_d and P_d at any circumstance despite the value was different, which was in accordance with the result we directly inducted from the experiment.     

Nonaqueous emulsion polymerization: A practical synthetic route for the production of molecularly imprinted nanospheres

Monodisperse, molecularly imprinted nanospheres were synthesized by nonaqueous (mini)emulsion polymerization using a standard monomer mixture of methacrylic acid and ethylene dimethacrylate containing the drug propranolol as a template. The preparation conditions (solvent, amount of surfactant, and amount of employed template) were extensively varied in order to assess their effect on the properties of the resulting polymer nanoparticles. The molecular recognition capability of the nanospheres was evaluated in batch rebinding experiments, and the effect of the nanosphere preparation conditions as well as of the reaction conditions was investigated. In this way, optimal preparation protocols for molecularly imprinted nanoparticles under nonaqueous conditions with the use of a nonionic emulsifier were identified, which lead to nanospheres with a diameter of around 100 nm having an enhanced capacity of specific template rebinding compared to both nonimprinted nanospheres and to particles obtained by emulsion polymerization in water. Best results were obtained with nanospheres prepared in N,N‐dimethylformamide/n‐hexane with a high functional monomer to template ratio. The enantioselectivity of the rebinding process was also demonstrated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Preparation and catalytic performances of a molecularly imprinted Ru-complex catalyst with an NH2 binding site on a SiO2 surface

A catalyst surface with an active metal site, a shape-selective reaction space, and an NH(2) binding site for o-fluorobenzophenone was designed and prepared by the molecular imprinting of a supported metal complex on a SiO(2) surface. A ligand of a SiO(2)-supported Ru complex that has a similar shape to the product of o-fluorobenzophenone hydrogenation was used as a template. An NH(2) binding site for o-fluorobenzophenone was spatially arranged on the wall of a molecularly imprinted cavity with a similar shape to the template. The structures of the SiO(2)-supported and molecularly imprinted Ru catalysts were characterized in a step-by-step manner by means of solid-state magic angle spinning (MAS) NMR, XPS, UV/Vis, N(2) adsorption, XRF, and Ru K-edge EXAFS. The molecularly imprinted Ru catalyst exhibited excellent shape selectivity for the transfer hydrogenation of benzophenone derivatives. It was found that the NH(2) binding site on the wall of the molecularly imprinted cavity enhanced the adsorption of o-fluorobenzophenone, of which the reduction product was imprinted, whereas there was no positive effect in the case of o-methylbenzophenone, which cannot interact with the NH(2) binding site through hydrogen bonding.     

Preparation of a novel molecularly imprinted polymer using a water-soluble crosslinking agent

A molecularly imprinted polymer was prepared using a water-soluble crosslinking agent. An ionic complex was utilized as the assembly for the template molecule and the functional monomer, and water as porogenic solvent during preparation of the imprinted polymer. The results of chromatographic evaluations for the prepared polymer suggested that the polymer had much lower hydrophobicity compared with usual octadecyl group bonded silica or the usual molecular imprinted polymer prepared from ethyleneglycol dimethacrylate, and the selective recognition ability for template molecule in the completely aqueous condition.     

伊诺沙星分子印迹聚合物的制备及分子识别性能研究

以伊诺沙星为印迹分子、甲基丙烯酸为功能单体、季戊四醇三丙烯酸酯为交联剂,合成了对伊诺沙星有较好选择性的印迹聚合物。利用铽敏化荧光,通过静态平衡结合法和Scatchard分析法研究了此印迹聚合物的结合能力和选择性,结果表明印迹聚合物对伊诺沙星有较高的亲和性和选择性。