Binding capacity of molecularly imprinted polymers and their nonimprinted analogs

Molecularly imprinted polymers bind their target compounds at binding sites. The binding sites are typically based on some type of functional group, such as carboxyl group. The total amount of such functional groups and their distribution into available and unavailable groups is not well known. The total binding capacity is usually indirectly determined from adsorption isotherms, which are measured much below the theoretical binding capacity. This work shows that in a variety of differently prepared, methacrylic acid based molecularly imprinted and nonimprinted polymers, all carboxylic groups used for the polymer synthesis are retained in the polymer, 80–90% of them can be accessed by strong bases and essentially the same amount can be used for adsorption of weak bases. This high level of adsorption can only be achieved, however, if the adsorbed weak base is strong enough, if the polymer is sufficiently elastic and if the solvent does not compete too strongly for the binding sites. These results may explain why the maximum binding capacities obtained from isotherm measurements are usually not equal to the total amount of available binding sites. This study confirms the usefulness of nonimprinted polymers at high loadings.     

A study of competitive molecular interaction effects on imprinting of molecularly imprinted polymers

The work herein reports on an approach to obtain molecularly imprinted polymers (MIPs) for Atmer 129, an antistatic added to polyolefins and a previously non imprinted template with intra molecular H-bonding capability. The template–monomer interactions occurring in pre- and post-polymerization media were analyzed by FTIR and ATR-FTIR, respectively. After the prepolymerization study, the synthesis conditions were discussed and suitable porogens and potential template:monomer stoichiometries were suggested. The imprinting efficiency and selectivity of MIPs were evaluated in batch assays by HPLC or UPLC and compared with thermal behavior and morphological characteristics checked by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The best results were obtained for MIPs synthesized at 60 °C. A relation between imprinting effect and template shape recognition was suggested by selectivity studies. The major conclusion, which has been drawn from FTIR and DSC studies, is that independently of the H-bonding strength between Atmer 129 and monomer, the template started to crystallize out during the polymerization reaction, thus reducing the imprinting effect.     

Molecularly imprinted polymers: modulating molecular recognition by a thermal phase transition in the binding framework

The concept used to realize the modulation of molecular recognition in a molecularly imprinted polymer is presented. Creating a thermal phase transition within the binding framework, the imprinted material was prepared using Boc-phenylalanine as the template and pNIPAM as the sensitive unit. The results indicate that such a transition causes a clear modulation in the recognition behavior of the prepared polymer which depends on the operation temperature. At a relatively low temperature, the prepared polymer acts like a traditionally imprinted one, showing a highly specific recognition for the imprint species. However, the prepared polymer does not present any notable resolution at 40 degrees C. This recognition behavior is comparable to a process that can be switched on and off, thus making modulated recognition feasible.     

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.     

分子印迹聚合物吸附性能的影响因素探讨

分子印迹聚合物具有对特定分子的亲和性和高选择性,稳定性好、使用寿命长、应用范围广等特点,因此在很多领域,如色谱分离[1]、固相萃取[2]、仿生传感[3]、模拟酶催化[4]、临床药物分析[5]、膜分离[6]等得到日益广泛的研究和应用。影响分子印迹聚合物与模板分子之间识别作用的因     

Comparison of binding behavior for molecularly imprinted polymers prepared by hierarchical imprinting or Pickering emulsion polymerization

The aim of this study was the evaluation of the binding performances and selectivity of molecularly imprinted beads prepared toward several penicillins (i) by hierarchical bulk polymerization in the pores of template‐grafted silica microbeads (hMIPs) and (ii) by Pickering emulsion polymerization in the presence of template‐decorated silica nanobeads (pMIPs). 6‐Aminopenicillanic acid was chosen as the common fragmental mimic template. Both approaches produced micron‐sized polymeric beads with good recognition properties toward the target ligands whereas the selectivity pattern appeared quite different. The polymer prepared by the Pickering emulsion approach showed binding properties similar to imprinted beads prepared by hierarchical approach. Equilibrium binding constants changed their values from 0.1–0.2 × 10⁶ (hMIPs) to 0.2–0.6 × 10⁶ M^?1 (pMIPs), while the binding site densities changed from 3.7–4.8 (hMIPs) to 0.3–0.55 μmol/g (pMIPs). Compared to the hierarchical polymerization, Pickering emulsion polymerization represents a more practical approach when a template mimic needs to be used.     

Surface ligands in the imprinting and binding of molecularly imprinted cross-linked micelles

Molecular recognition in water is challenging but water-soluble molecularly imprinted nanoparticle (MINP) receptors were produced readily by double cross-linking of surfactant micelles in the presence of suitable template molecules. When the micellar surface was decorated with different polyhydroxylated ligands, significant interactions could be introduced between the surface ligands and the template. Flexible surface ligands worked better than rigid ones to interact with the polar moiety of the template, especially for those template molecules whose water-exposed surface is not properly solvated by water. The importance of these hydrophilic interactions was examined in the context of different substrates, density of the surface ligands, and surface-cross-linking density of the MINP. Together with the hydrophobic interactions in the core, the surface hydrophilic interactions can be used to enhance the binding of guest molecules in water.     

对-特辛基酚表面印迹聚合物的制备及吸附性能评价

以对-特辛基酚为模板、甲基丙烯酸为功能单体制备了对-特辛基酚表面印迹聚合物.采用扫描电子显微镜、紫外光谱以及红外光谱对印迹聚合物进行表征,通过平衡吸附实验对聚合物的吸附性能进行评价.结果表明:该分子印迹聚合物对对-特辛基酚具有较大的吸附容量和良好的选择性,其最大吸附量Qmax约为86.12mg/g.     

Surface imprinted polymers for oil denitrification with the combination of computational simulation and multi‐template molecular imprinting

Multi‐template molecular imprinting technique was employed for the theoretical study about industrial oil denitrification. Prior to the preparation of multi‐template molecularly imprinted polymers (MT‐MIPs), density functional theory was used for simulating the imprinted pre‐assembly systems composed of template (aniline, indole, or 3‐methylinndole) and monomer [methacrylic acid, acrylamide (AM), and 4‐vinylpyridine]. MT‐MIPs were synthesized as surface MIPs simply and successively by seeded emulsion polymerization or two‐stage precipitation polymerization. The experimental results were consistent with the simulative results, which demonstrated that AM was more suitable monomer together. In addition, seeded emulsion polymerization synthesized MT‐MIPs with better performance compared with two‐stage precipitation polymerization. The adsorption kinetics and adsorption isotherm of MT‐MIP prepared with AM using seeded emulsion polymerization were fitted with different models. The fitting results indicated that pseudo‐second‐order kinetics model and Freundlich isotherm model were suitable for describing the adsorption process of AM seeded emulsion polymerization. This study will provide a certain guidance and theoretical basis for introducing the combination of multi‐template molecular imprinting technique and computational simulation into the field of industrial denitrification. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of protein imprinting in hydrogel-based molecularly imprinted polymers (HydroMIPs)

We have developed a strategy to produce molecularly imprinted polymers based on polyacrylamide hydrogels for the selective imprinting of bovine haemoglobin (BHb). For the first time, we have explored in detail a variety of template removal strategies including varying ratios of sodium dodecylsulphate:acetic acid (SDS:AcOH) and also the use of a trypsin digest. The optimum ratio of SDS:AcOH was found to be a 10% (w/v):10% (v/v) for the most effective template removal. This resulted in >90% (imprinting efficiency) of re-loaded template (protein) molecule being selectively bound within the MIP. At 15%:15% of SDS:AcOH, although there was even more initial template removal, subsequent re-binding studies showed a decrease in imprinting efficiency (67.9%). Trypsin solutions were also used as a method of template removal. Up to 87.4% of template was reproducibly removed initially; however, the imprinting efficiency was only 20.4%. The high selectivity of the BHb HydroMIP to BHb compared with other structural analogues (namely cytochrome C and myoglobin) was successfully demonstrated.     

Investigation of imprinting parameters and their recognition nature for quinine-molecularly imprinted polymers

A series of molecularly imprinted polymers (MIPs) was prepared using quinine as the template molecules by bulk polymerization. The presence of monomer-template solution complexes in non-covalent MIPs systems has been verified by both fluorescence and UV-vis spectrometric detection. The influence of different synthetic conditions (porogen, functional monomer, cross-linkers, initiation methods, monomer-template ratio, etc.) on recognition properties of the polymers was investigated. Scatchard analysis revealed that two classes of binding sites were formed in the imprinted polymer. The corresponding dissociation constants were estimated to be 45.00 micromol l(-1) and 1.42 mmol l(-1), respectively, by utilizing a multi-site recognition model. The binding characteristics of the imprinted polymers were explored in various solvents using equilibrium binding experiments. In the organic media, results suggested that polar interactions (hydrogen bonding, ionic interactions, etc.) between acidic monomer/polymer and template molecules were mainly responsible for the recognition, whereas in aqueous media, hydrophobic interactions had a remarkable non-specific contribution to the overall binding. The specificity of MIP was evaluated by rebinding the other structurally similar compounds. The results indicated that the imprinted polymers exhibited an excellent stereo-selectivity toward quinine.     

冬凌草甲素分子印迹聚合物的制备及分子识别性能研究

以抗肿瘤药物分子冬凌草甲素为模板,甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(ED-MA)作交联剂,采用沉淀聚合法和本体聚合法,制备对冬凌草甲素具有特定亲和选择性的分子印迹聚合物,并用激光粒度扫描和扫描电镜对聚合物的粒径和表面形貌进行了表征,采用平衡结合实验评价了两类分子印迹聚合物的吸附性能.结果表明,与使用...     

三氯生分子印迹传感器的制备及其性能研究

应用分子印迹技术, 以邻苯二胺为功能单体、三氯生为模板, 用循环伏安法在玻碳电极表面合成了性能稳定的三氯生分子印迹聚合膜, 并用方波伏安法对此印迹传感器进行了分析应用研究.     

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.     

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.     

Chromatographic characterization of a molecular imprinted polymer binding cortisol

A cortisol-binding polymer was prepared by utilising a non-covalent molecular imprinting polymerisation technique. The obtained polymer was packed in a high-performance liquid chromatography (HPLC) column; the selectivity was studied by liquid chromatography, eluting cortisol, cortisone, corticosterone, progesterone, 11-ketoprogesterone, 11alpha-hydroxyprogesterone, 17alpha-hydroxyprogesterone, cortisol 21-hemisuccinate, and cortisol 21-acetate with chloroform, containing 0.5% (v/v) acetic acid, as mobile phase. The mechanism of molecular imprinting was confirmed and a good selectivity for cortisol, with limited recognition for cortisone and 11alpha-hydroxyprogesterone, was found.     

盐酸强力霉素分子印迹聚合物的制备及分子识别性能

以盐酸强力霉素(DC)为模板分子、甲基丙烯酸为功能单体、乙二醇二甲基丙烯酸酯为交联剂、四氢呋喃(THF)为溶剂.采用本体聚合法制备了DC的分子印迹聚合物.在水溶液中,采用平衡结合方法和Scatchard模型评价了该聚合物的结合特性及识别机理,并考察了DC分子印迹聚合物的选择性吸附能力.结果表明,在所研究的浓度范围内,D...     

Molecular recognition in imprinted polymers: thermodynamic investigation of analyte binding using microcalorimetry

This study aimed at elucidating the interaction mechanism between an imprinted polymer and its template in aqueous environment with thermodynamic aspects. The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was chosen as a model template to imprint a co-polymer of 4-vinylpyridine (4-VP) and ethyleneglycol dimethacrylate. Equilibrium binding isotherm analysis and isothermal titration microcalorimetry were used to quantify the contribution of enthalpy and entropy to the binding process, identify the nature of the interactions involved and confirm the existence of binding pockets with shape-complementarity to the template. For the binding process of 2,4-D to the imprinted polymer, we postulate three subprocesses: (1) dehydration of the binding pocket and of the 2,4-D, (2) adsorption of 2,4-D, and (3) rearrangement of the water molecules from the dehydration process. We found that binding in aqueous environment was due to the cumulative effect of pi-stacking and electrostatic interactions between the template and the functional monomers. At pH<6, entropy is the dominating driving force, while at pH>6 where the highest difference in binding between the imprinted and a non-imprinted reference polymer was observed, the enthalpy change accounts for most of the binding free energy. The developed microcalorimetric method sheds light on the binding mechanism of analyte molecules with imprinted polymers, in particular if the polymers are used in aqueous solvents.