Simple NMR experiments as a means to predict the performance of an anti-17α-ethynylestradiol molecularly imprinted polymer

Rapid determination of metanil yellow in turmeric using a molecularly imprinted polymer dispersive solid-phase extraction and visible light spectrophotometry

The present study aimed to develop a sensitive and available method for determining metanil yellow (MY) as an adulterating agent in food samples. Solid-phase extraction was chosen for pre-concentrating metanil yellow prior to its determination using a validated UV-spectrophotometric method. The precipitation polymerization method was applied to synthesize a range of molecularly imprinted polymers (MIPs) for selective extraction of MY. Polymers were characterized by SEM and FTIR and investigated for MY extraction through batch rebinding experiments. The extraction process was optimized in the term of pH, time, capacity, and the desorbing solvent. Results of this study showed the critical role of template/functional monomer ratio in the preparation of the MIPs. The developed MIP solid-phase extraction/UV-spectrophotometric method was employed for determining MY in spiked samples and showed 88.10-92.76% recovery for turmeric samples containing 0.1-10 mg/kg MY. The developed method was shown selective for MY in the presence of another azo dye.

Imprinted polymers for chiral resolution of (+/-)-ephedrine. Part 3: NMR predictions and HPLC results with alternative functional monomers

The monomers trifluoromethacrylic acid (TFMAA), 2-hydroxyethylmethacrylate (HEMA) and itaconic acid (IA) have been compared for the molecular imprinting of (-)-ephedrine. Data from NMR titrations were fitted using the program HypNMR to obtain association constants for monomer-template (M-T) complexes of different stoichiometries. These were used to predict the speciation in imprinting mixtures with porogen and cross-linker, and molecularly imprinted polymers (MIPs) were fabricated and their ability to bind (-)-ephedrine and its enantiomer were assessed by high performance liquid chromatography (HPLC). TFMAA and IA interact more strongly with ephedrine than does MAA, yet MIPs made with each of these monomers perform worse. With TFMAA, covalent monomer-template adducts and TFMAA oligomers, present in the polymerisation mixture, may detract from the MIP recognition properties. With IA, the relative flexibility of the monomer may be an issue. HEMA interacts more weakly with ephedrine, and HEMA-based MIPs exhibit much worse retention, and poorer recognition, than those based on MAA. It may be useful to use a higher ratio of M : T in the case of HEMA because the monomer interacts with the cross-linker EDMA.

Retention behavior of phenoxyacetic herbicides on a molecularly imprinted polymer with phenoxyacetic acid as a dummy template molecule

Molecular imprinted polymers (MIPs) binding with phenoxyacetic acid (PA) as a dummy template molecule were synthesized via thermal initiation in aqueous medium. The retention behaviors of benzoic acid (BA), PA, 2-methyl-4-chlorophenoxyacetic acid (MCPA), 4-chlorophenoxyacetic acid (4-CPA), and 2,4-dichlorophenoxyacetic acid (2,4-D) on this MIP column indicate that this material can selectively retain phenoxyacetic herbicides. To investigate these recognition mechanisms, the interactions between the functional monomer 4-vinylpyridine (4-VP) and PA or 2,4-D were investigated by computational modeling. (1)H NMR spectroscopy of 2,4-D titrated by 4-VP was recorded. The chemical shift of the 2,4-D acidic proton (12.15-14.32ppm) shows the existence of the ion-pair interaction. This kind of polymers could be useful as stationary phases to extract 2,4-D, 4-CPA or MCPA and avoid leakage of a trace amount of target analyte remaining in the MIPs.

Investigation of the nature of MIP recognition: The development and characterisation of a MIP for Ibuprofen

This paper describes the rational design, generation and testing of a molecularly imprinted polymer specific for Ibuprofen. Ibuprofen is a member of the class of drugs termed non-steroidal anti-inflammatory drugs (NSAIDS). In the present study, Ibuprofen was used as a template molecule for the preparation of molecularly imprinted polymers. A MIP has been produced which is capable of recognising Ibuprofen in aqueous media. Furthermore, Ibuprofen can be selectively extracted from aqueous conditions by molecularly imprinted solid phase extraction (MISPE). Recoveries were typically high (>80%) and good selectivity for Ibuprofen over structurally related analogues was seen. Moreover, the nature of the recognition between MIP and template has been investigated by NMR and molecular modelling to analyse whether or not it is possible to predict how well a given MIP will perform under set conditions. In addition, the physical characteristics of the MIP have been investigated including the particle size distribution on exposure of the MIP to different solvents. This has been related to the ability of the MIP to rebind Ibuprofen under the same conditions. The data from the characterisation of the MIP has been used to further enhance the understanding of the nature of MIP recognition.

Study on the mechanism of binding specificity of metoclopramide-imprinted polymers

A series of metoclopramide (MCP)-imprinted polymers utilizing methacrylic acid or 2-vinylprindine (2-VP) as functional monomer and chloroform, acetonitrile or methanol as porogen were prepared. The affinity and specificity of these polymers were evaluated by equilibrium binding experiments. Proton NMR model studies on interactions between the template and functional monomer analogues, acetic acid and d5-pyridine, were performed in the same solvents that were used as porogens for the molecularly imprinted polymers (MIPs). A correlation was found to exist between the binding strength and specificity of a particular polymer and the extent of monomer-template interactions shown by the corresponding NMR spectrum. So, a useful means is provided to predict the performance of a MIP in this paper. Based on the results of NMR experiments and selectivity experiments, the role of functional groups of the template in the formation of complementary interacting sites in the polymer in different porogens was discussed, and the mechanism of molecular recognition of the MIPs was proposed.

Solvent effects in the preparation of molecularly imprinted polymers for melatonin using N-propionyl-5-methoxytryptamine as the pseudo template

To clarify the role of diluents in the preparation of molecularly imprinted polymers utilizing only hydrogen bonding, we investigated the effects of diluents by using different solvents. Melatonin (N-acetyl-5-methoxytryptamine), an amide bond and indole ring-containing hormone was chosen as the target molecule. N-Propionyl-5-methoxytryptamine was used as the pseudo template, methacrylic acid as the functional monomer, and solvents were used as diluents. Interactions between the template, the functional monomer, melatonin, and the solvents, were observed by 1H NMR spectroscopy. The polymers were evaluated by high-performance liquid chromatography. The results suggest the hydrogen bonding-acceptor capacity of the solvent is the most important factor in the preparation of molecularly imprinted polymers for hydrogen bonding-donating molecules. Hydrogen bonding between the template, the functional monomer, and solvent can be estimated from the chemical shifts in 1H NMR spectra of those molecules in the solvent.

Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

Over 1450 references to original papers, reviews and monographs have herein been collected to document the development of molecular imprinting science and technology from the serendipitous discovery of Polyakov in 1931 to recent attempts to implement and understand the principles underlying the technique and its use in a range of application areas. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by papers dealing with fundamental aspects of molecular imprinting and the development of novel polymer formats. Thereafter, literature describing attempts to apply these polymeric materials to a range of application areas is presented.

Removal of estrogenic pollutants from contaminated water using molecularly imprinted polymers

A synthetic molecularly imprinted polymer (MIP) sorbent for estrogenic compounds was prepared using a noncovalent imprinting technique. MIP microspheres sized from 1 to 2 microm were synthesized in acetonitrile by using alpha-estradiol as the template, acrylamide as the functional monomer, and trimethylpropanol trimethacrylate as the cross-linker. When compared with the nonimprinted polymer (NIP), the MIP showed outstanding affinity toward alpha-estradiol in aqueous solution with a binding site capacity (B(max)) of 380 nmol mg(-1) MIP, imprinting effect of 35, and a dissociation constant (Kd) of 38 microM. The MIP exhibited significant binding affinity toward other related estrogenic compounds such as beta-estradiol, diethylstilbestrol, estriol, and estrone, suggesting that this material may be appropriate for treating a complex mixture of estrogenic pollutants. The feasibility of removing estrogenic compounds from environmental water by the MIP was demonstrated using lake water spiked with alpha-estradiol. In addition, the MIP reusability without any deterioration in performance was demonstrated for at least five repeated cycles.

Analyzing the Mechanisms of Selectivity in Biomimetic Self-Assemblies via IR and NMR Spectroscopy of Prepolymerization Solutions and Molecular Dynamics Simulations

Molecularly imprinted polymers (MIPs) for 2,4-dichlorophenoxyacetic acid were synthesized via a noncovalent approach with 4-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as cross-linker in a methanol/water mixture. Templated polymers synthesized in this self-assembly approach rely on complex formation between the target analyte and functional monomers in porogenic solution prior to radical polymerization. Consequently, the achievable selectivity is governed by the nature and stability of these complexes. The nature of noncovalent interactions responsible for complex formation during imprinting of the template 2,4-dichlorophenoxyacetic acid (2,4-D) with the functional monomer 4-vinylpyridine has been investigated. Fourier transform infrared and 1H NMR spectroscopies provide the fundamental analytical basis for rationalizing the mechanisms of recognition during the imprinting process probing the governing interactions for selective binding site formation at a molecular level. Molecular modeling studies in explicit solvent (chloroform and water) corroborate the importance of hydrogen bonding in aprotic solvents and of hydrophobic interactions in protic media in agreement with the experimental spectroscopic investigations of prepolymerization solutions. Furthermore, chromatographic studies of the synthesized MIPs provided insight on the importance of size, shape, and functionality during selective 2,4-D rebinding processes confirming the results obtained during the prepolymerization studies.

Formulation of Cocaine-Imprinted Polymers Utilizing Molecular Modelling and NMR Analysis

Molecular imprinted polymers (MIPs) have distinctive features that make them attractive as an inexpensive, reusable, and robust field-based detection system for illicit substances. Optimizing MIP performance is traditionally attained by the synthesis and evaluation of a plethora of individual formulations. A non-covalently imprinted polymer for cocaine has been prepared using a commercially available molecular modelling package (Spartan 02) to predict energetically favourable monomer–template interactions between the target (T) and two different functional monomers (FM)—methacrylic acid (MAA) and 4-vinylpyridine (4VP). NMR studies undertaken to assess target–monomer behaviour in solution were in good agreement with the computational data. MIPs involving three target-to-functional monomer ratios (1 : 2, 1 : 6, and 1 : 14) were prepared and evaluated. Target rebinding was found to be most favourable in the 1 : 2 formulation with a target-selective binding of 0.48 ppm and an imprinting factor (I) of 2.8 obtained for 10 mg of test polymer.

Configurational biomimesis in drug delivery: molecular imprinting of biologically significant molecules

This review focuses on trends in the macromolecular recognition of biologically significant molecules (e.g., drugs, amino acids, steroids, nucleotide bases, carbohydrates, etc.) via molecular imprinting methods. An extensive list of prior art including type of functional monomers and crosslinkers for each biomolecule imprinted polymer is presented. Representative samples of receptor-ligand dissociation constants and polymer capacities are presented as well as typical values that occur in classes of biological recognition systems. Imprinting technology has direct impact in enhanced drug loading of controlled-release carriers for the sustained release of therapeutic agents as well as robust biosensors for novel therapeutic and diagnostic devices. This review also discusses the future of designed recognition, configurational biomimesis within polymeric gels, and highlights recent efforts toward integrating imprinted polymers in controlled drug delivery systems and sensing devices. In particular, the application of imprinted polymers for sustained release, enhanced loading capacity, and enantioselective loading or release are discussed. This article also highlights the most important problems to be solved in the design of synthetic recognition-based networks for biological molecules.

Multidimensional on-line sample preparation of verapamil and its metabolites by a molecularly imprinted polymer coupled to liquid chromatography–mass spectrometry

A new molecularly imprinted polymer (MIP) material was synthesized selective for verapamil and utilized for on-line metabolic screening of this common calcium antagonist in biological samples. Since some metabolites of verapamil have also shown pharmacological properties, a selective and sensitive sample preparation approach that provides a metabolic profile in biologically relevant samples is important. The MIP material was coupled on-line to a restricted access material (RAM) precolumn. The multidimensional nature of this set-up removed large matrix interferents such as proteins from the sample, while the selectivity of the MIP enabled further cleanup of the smaller analytes. The selectivity and extraction efficiency of the MIP for verapamil and its metabolites was evaluated in various biological matrices, such as cell cultures and urine. The experimental set-up with the developed method enabled the direct injection of biological samples for the selective isolation, preconcentration, identification and analysis of verapamil and its phase I metabolites by LC-MS(n). This multidimensional approach provided much qualitative information about the metabolic profile of verapamil in various biological matrices. An analytical method was developed for the quantification of verapamil and gallopamil in urine, plasma and cell culture. Acceptable linearity (R(2)=0.9996, 0.9982 and 0.9762) with an average injection repeatability (n=3) of 10, 25 and 15% R.S.D. was determined for urine, plasma and cell culture, respectively. This is the first application of the procedure for the selective metabolic screening of verapamil in biological samples.