Molecularly imprinted polymer hydrogels displaying isomerically resolved glucose binding

Imprinting of Stöber particles for chirally-resolved adsorption of target monosaccharides and disaccharides

Soft imprinting of silica particles using sugar surfactants targets chirally resolved binding of saccharides.

Role of Mechanical Factors in Applications of Stimuli-Responsive Polymer Gels - Status and Prospects

Due to their unique characteristics such as multifold change of volume in response to minute change in the environment, resemblance of soft biological tissues, ability to operate in wet environments, and chemical tailorability, stimuli responsive gels represent a versatile and very promising class of materials for sensors, muscle-type actuators, biomedical applications, and autonomous intelligent structures. Success of these materials in practical applications largely depends on their ability to fulfill application-specific mechanical requirements. This article provides an overview of recent application-driven development of covalent polymer gels with special emphasis on the relevant mechanical factors and properties. A short account of mechanisms of gel swelling and mechanical characteristics of importance to stimuli-responsive gels is presented. The review highlights major barriers for wider application of these materials and discusses latest advances and potential future directions toward overcoming these barriers, including interpenetrating networks, homogeneous networks, nanocomposites, and nanofilamentary gels.

Boronate-Affinity Glycan-Oriented Surface Imprinting: A New Strategy to Mimic Lectins for the Recognition of an Intact Glycoprotein and Its Characteristic Fragments

Lectins possess unique binding properties and are of particular value in molecular recognition. However, lectins suffer from several disadvantages, such as being hard to prepare and showing poor storage stability. Boronate-affinity glycan-oriented surface imprinting was developed as a new strategy for the preparation of lectin-like molecularly imprinted polymers (MIPs). The prepared MIPs could specifically recognize an intact glycoprotein and its characteristic fragments, even within a complex sample matrix. Glycan-imprinted MIPs could thus prove to be powerful tools for important applications such as proteomics, glycomics, and diagnostics.

Synthesis of a molecularly imprinted polymer to isolate glucosamine from plant extracts by an ionic-non-covalent dual approach

OBJECTIVE

The objective of this study was to synthesize a novel glucosamine-imprinted sorbent based on ionic and non-covalent dual approach to purify glucosamine from chicory root extracts.

METHODS

The synthesis of the molecularly imprinted polymer was optimized in terms of choice of monomers, porogen, cross-linker and initiator to have the best recognition as possible for targeted molecule. The sorbent obtained was characterized by nitrogen sorption (BET), scanning electron microscopy (SEM) and solid-phase extraction (SPE) to plot adsorption isotherms. The selectivity of polymer between glucosamine and interfering salt as ammonium sulphate was calculated. Extraction procedure was optimized in terms of loading, washing and elution solvents, to have the best recovery of glucosamine. Compounds were analysed by HPLC-UV after chemical derivatization.

RESULTS

The results showed that the optimal conditions of extracting glucosamine on this new type of sorbent were as follows: percolation of plant extract in EtOH/aqueous HCl pH 3, washing of cartridge with water and elution of compound of interest with aqueous acetic acid solution at 5%. The recoveries of glucosamine were around 53% and 70%, from aqueous standard solution and aqueous chicory roots extracts, respectively, on the molecularly imprinted polymer. And, only 11% and 7% of the ammonium sulphate were recovered from standard solution and chicory roots extract, respectively.

CONCLUSION

The use of the MIP as solid-phase extraction sorbent was able to extract preferentially glucosamine from structural analogues and ammonium salt. Assays on chicory roots extracts were carried out, and the MIP showed good results allowing the transfer methodology at semi-industrial scale for cosmetic companies. The optimized protocol of extraction of glucosamine allowed using only eco-friendly solvents, as ethanol, water and acetic acid.

Molecularly imprinted bioartificial membranes for the selective recognition of biological molecules. Part 2: release of components and thermal analysis

Molecularly imprinted membranes imprinted for a large-molecular-weight protein were realised using a blend of natural and synthetic polymers. Bioartificial membranes of synthetic (poly(ethylene-co-vinyl alcohol)-EVAL, Clarene) and biological (Dextran) polymers, molecularly imprinted with alpha-amylase as the template, were prepared and investigated. Dimethyl sulfoxide (DMSO) solutions of the alpha-amylase template, Clarene and Dextran were mixed under stirring in the desired proportions and dipped in DMSO (solvent)/water (non solvent) mixture, to obtain the phase separation. The release of Clarene, Dextran and alpha-amylase in the inversion baths was quantified by spectrophotometric methods and final composition of membranes was established. To study the interactions between the polymer components and between polymeric materials and the template, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were carried out. Results indicated that stable and continuous bioartificial membranes of Clarene and Dextran can be obtained, whereby calorimetric analysis suggested the presence of high interaction between alpha-amylase and the Clarene component.

The relevance of the transfer of molecular information between natural and synthetic materials in the realisation of biomedical devices with enhanced properties

Past and recent attempts to introduce in synthetic polymers molecular information from natural substances through simple blending, template polymerization and molecular imprinting are reviewed. The most promising approaches that can open the way to the realisation of new materials with improved biocompatibility, antibody- or enzyme-like performances are analysed more deeply. The realisation of bioartificial blends from natural and synthetic polymers, molecularly imprinted nanospheres or membranes that can act as recognition element in (bio)sensing devices, as synthetic enzymes or as key constituents of body fluids purification tools is presented in order to make the reader aware of the fascinating possibilities that these techniques make available to the biomedical science and engineering in the close future. The last part of the paper describes recent attempts to insert recognition elements for large molecules as proteins, DNA segments, viruses or whole cells in synthetic polymer systems, in order to develop new systems in the treatments of diseases and for tissue-engineering applications.

Detection of p53 gene point mutation using sequence-specific molecularly imprinted PoPD electrode

An amperometric sequence-specific molecularly imprinted single-stranded oligodeoxyribonucleotide (ss-ODN) biosensor was fabricated and characterised in this study. Using ss-ODN as the template and o-phenylenediamine as the functional monomer, the ODN biosensor was fabricated by an electropolymerisation process on an indium-tin oxide (ITO) coated glass substrate. The template ss-ODN was washed out of the ss-ODN/poly(o-phenylenediamine)(PoPD)/ITO electrode using sterilised basic ethanol-water. The resulting ss-ODN imprinted PoPD/ITO electrode was characterised using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The amperometric responses, i.e., Δi as a function of the target ss-ODN concentration was studied. The biosensor using ss-ODN imprinted PoPD/ITO as the working electrode showed a linear Δ current response to the target ss-ODN concentration within the range of 0.01-300 fM. The biosensor showed a sensitivity of 0.62 μA/fM, with a response time of 14s. The present novel molecularly imprinted ss-ODN biosensor could greatly benefit in terms of cost-effectiveness, storage stability, ultra sensitivity and selectivity together with the potential for improved commercial genetic sensors.

Isomeric glucose recognition using molecularly imprinted polymer hydrogels

The goal of this research is to produce molecular imprinted polymers (MIPs), which selectively bind glucose over other sugars. MIP hydrogels against glucose exhibited binding capacities in excess of 0.6 grams of glucose per gram of dry gel in a 100 % DI H2O glucose solution, as well as in a 50–50 % glucose-fructose solution mixture. Equilibrium binding capacities of fructose were lower than those observed with respect to glucose, indicating an isomeric preference for the binding of glucose over fructose. Although it is expected that imprinted cavities will be distorted due to the swelling of the hydrogel in water, our experiments show that even the swollen gels exhibit remarkable glucose recognition. This synthetic and characterization methodology for MIPs might thus offer exciting avenues for novel biomimetic recognition and isomeric separation techniques.

Recognition and Absorption of the Water-soluble X-ray Contrast Medium Iodixanol using Molecularly Imprinted Polymers for Biomedical Applications

This work presents the study on the recognition and absorption of the water-soluble X-ray contrast medium iodixanol in aqueous solution using synthetic molecularly imprinted polymers (MIPs). A non-covalent imprinting technique was applied to prepare iodixanol-imprinted polymers using 4-vinylpyridine as the functional monomer and ethylene glycol dimethacrylate as the cross-linker. The effects of quantity of iodixanol templates, the crosslink density, and the solvent were studied in terms of the binding capacity and imprint effect of the polymers. UV-vis spectrometric analysis shows that the highest binding capacity achieved is 284 mg iodixanol per gram of dry polymer, which is 8.8 times higher than the binding capacity of the non-imprinted control polymers (NIPs). SEM and BET surface analysis have also been performed to investigate the effect of morphology and porosity on the binding capacities of polymers.

Absorption performance of iodixanol-imprinted polymers in aqueous and blood plasma media

This paper presents the preparation and absorption performance of iodixanol-imprinted polymers in aqueous and blood plasma media in vitro for biomedical applications. The imprinted polymers were prepared by non-covalent imprinting of iodixanol in a matrix of poly(4-vinylpyridine) crosslinked by ethylene glycol dimethacrylate. The binding capacities (BCs) were investigated as a function of template-to-monomer, as well as monomer-to-crosslinker, ratios in the polymerization, and the solvent type. The highest BC of iodixanols achieved from the optimized imprinted polymer in the aqueous solution is 284mgg(-1) dry polymer with an imprinting effect (IE) 8.8 times higher than that of the non-imprinted polymer. In blood plasma, the BC of this polymer is slightly reduced to 232mgg(-1) with a smaller IE 4.3 times higher than that of the control polymer. The BCs of molecularly imprinted polymers as a function of the initial assay solution concentration as well as the examination time are also addressed. Surface analyses were additionally performed to characterize the surface morphologies and porosities of synthetic polymers. This work has demonstrated the feasibility of molecular imprinting of iodixanol, and the observed absorption performance of the imprinted polymers is encouraging for biomedical applications.

Supramolecular interactions in chemomechanical polymers

Molecular recognition is the basis for the operation of most biological functions; outside of nature, it has also been developed to a high degree of sophistication within the framework of supramolecular chemistry. More recently, selective noncovalent interactions, which constitute molecular recognition, are being used in intelligent new materials that transform chemical signals into actions, such as the release of drugs. The presence of supramolecular binding sites allows chemomechanical polymers to operate as sensors and actuators within a single unit without the need for any additional devices such as transducers or power supplies. A polymer can be designed so that a particular chemical substance, most often in aqueous surroundings, will trigger either a large expansion or a large contraction, depending on the mechanism. The translation of binding energy into mechanical motion can, with a suitable arrangement of the materials in tubes or on flexible films, be harnessed for unidirectional drives, flow control, the liberation of drugs, or the uptake of toxic compounds, among other applications. Miniaturization of the polymer particles allows one to enhance both the sensitivity and speed of the response, which is of particular importance in sensing. The basis for the selective response to external effector compounds, such as metal ions, amino acids, peptides, or nucleotides, is their noncovalent interaction with complementary functions covalently bound to the polymer network. With suitable polymers, selectivity between structural isomers, and even between enantiomers, as triggers can be achieved. As with supramolecular complexes in solution, the underlying interactions in polymers comprise a variety of noncovalent binding mechanisms, which are not easy to distinguish and quantify, and more so with polymers that are not monodisperse. In this Account, we present systematic comparisons of different polymers and effector classes that allow, for the first time, the characterization of these contributions in chemomechanical polymers: they comprise ion pairing, metal coordination, stacking, cation-pi, dispersive, and hydrophobic forces. In contrast, hydrogen bonding has a major role primarily in the hydrogel network structure itself. The fully reversible polymer volume changes are essentially determined by water uptake or release. In gels derived from boronic acid, glucose can serve as a cross-linking effector in promoting contractions via strong, reversible covalent bond formation in a highly distinctive manner. Cooperativity between two different effector compounds is more frequently seen with such polymers than in solution: it leads to logical AND gates by different motions of the particles, with a direct communication link to the outside world. For example, with a polymer that bears several recognition sites, triggering peptides induce motion only if Zn(2+) or Cu(2+) ions are simultaneously present. The molecular recognition mechanisms that cause volume changes in polymers share similarities with extensively studied supramolecular systems in solution, but there are also remarkable differences. In this Account, we bring the knowledge learned from solution studies to bear on our systematic analysis of polymeric systems in an effort to promote the effective harnessing of the forces involved in chemomechanical polymers and the smart materials that can be created with them.

Molecularly imprinted polymer of 5-methyluridine for solid-phase extraction of pyrimidine nucleoside cancer markers in urine

Normal and modified urinary nucleosides represent potential biomarkers for cancer diagnosis. To selectively extract modified nucleosides, we developed a molecularly imprinted polymer (MIP) of 5-methyluridine as selective material for molecularly imprinted solid-phase extraction (MISPE). The MIPs were obtained from vinyl-phenylboronate ester derivative of the template, acrylamide and pentaerythritol triacrylate co-polymer, and were tested in batch and cartridge experiments with aqueous samples. Our results indicated that the imprinted polymer was selective for pyrimidine nucleosides with a K(d) and a B(max) of 46 microM and 18 micromol/g, respectively. Finally, a MISPE of the most common pyrimidine nucleoside cancer markers in urine sample was realized.

Recent developments in sample preparation for chromatographic analysis of carbohydrates

Carbohydrates are a very important group of compounds due to their roles as structural materials, sources of energy, biological functions and environmental analytes; they are characterized by their structural diversity and the high number of isomers they present. While many advances have been made in carbohydrate analysis, the sample preparation remains difficult. This review aims to summarize the most important treatments which have been recently developed to be applied prior to the analysis of carbohydrates by chromatographic techniques. Due to the multiplicity of structures and matrices, many different techniques are required for clean-up, fractionation and derivatization. A number of new techniques which could be potentially adequate for carbohydrate characterization have also been revised.

From 3D to 2D: a review of the molecular imprinting of proteins

Molecular imprinting is a generic technology that allows for the introduction of sites of specific molecular affinity into otherwise homogeneous polymeric matrices. Commonly this technique has been shown to be effective when targeting small molecules of molecular weight <1500, while extending the technique to larger molecules such as proteins has proven difficult. A number of key inherent problems in protein imprinting have been identified, including permanent entrapment, poor mass transfer, denaturation, and heterogeneity in binding pocket affinity, which have been addressed using a variety of approaches. This review focuses on protein imprinting in its various forms, ranging from conventional bulk techniques to novel thin film and monolayer surface imprinting approaches.

Glucose-specific poly(allylamine) hydrogels--a reassessment

Polymer hydrogels synthesized by crosslinking poly(allylamine hydrochloride) with (+/-)-epichlorohydrin in the presence of d-glucose-6-phosphate monobarium salt do not show imprinting on the molecular level. A series of hydrogels was prepared using the following five templates: d-glucose-6-phosphate monobarium salt, d-glucose, l-glucose, barium hydrogen phosphate (BaHPO(4)), and d-gluconamide; a hydrogel was also prepared in the absence of a template. For all six hydrogels, batch binding studies were conducted with d-glucose, l-glucose, d-fructose, and d-gluconamide. The extent of analyte sugar binding was determined using (1)H NMR. Each hydrogel shows approximately the same relative binding affinity for the different sugar derivatives, and none displays selectivity for either glucose enantiomer. The results of the binding studies correlate with the octanol-water partition coefficients of the sugars, indicative that differential solubilities in the bulk polymer account for the binding affinities observed. Thus, in contrast to templated hydrogels prepared using methacrylate- or acrylamide-based reagents, true imprinting does not occur in this novel, crosslinked-poly(allylamine hydrochloride) system.

[New intelligent and targetted drug delivery systems. Pharmaceutical and biomedical applications]

Biomaterials are widely used in numerous medical applications. Chemical engineering has played a central role in this research and development. We review herein polymers as biomaterials, materials and approaches used in drug and protein delivery systems, materials used as scaffolds in tissue engineering, and nanotechnology and microfabrication techniques applied to biomaterials.

Molecularly imprinted polymers for tobacco mosaic virus recognition

Molecular imprinted Polymers (MIP) targeted for Tobacco mosaic virus (TMV) have been synthesized. Batch equilibrium studies using imprinted and non-imprinted polymer hydrogels in TMV and TNV solutions were conducted to determine virus-binding capacities. TMV-imprinted hydrogels showed increased binding to TMV (8.8 mg TMV/gpolymer) compared to non-imprinted hydrogels (4.2 mg TMV/gpolymer). Furthermore, TMV-imprinted hydrogels exhibited increased binding to TMV compared to TNV, while non-imprinted hydrogels bound similar amounts of TMV or TNV. This research has demonstrated that molecular imprinting of viruses can be used to selectively induce binding of target viruses based on shape differences of their virions.

Ionic effect on the binding of bilirubin to the imprinted poly(methacrylic acid-co-ethylene glycol dimethylacrylate)

A molecularly imprinted polymer (MIP) capable of detecting bilirubin was successfully synthesized. Bilirubin template was imprinted in poly(methacrylic acid-co-ethylene glycol dimethylacrylate) [poly(MAA-co-EGDMA)]. MAA and EGDMA were used as the monomer and the cross-linker, respectively. The optimal solvent conditions to maintain its stability were discussed. Solvent system based on ethylenediamine tetraacetic acid (EDTA) and ascorbic acid was compared with respect to the stability of bilirubin. pH and bilirubin concentration were both investigated for the bilirubin stability. Blue light as well as aeration was applied to inspect the regarding effects. The cross-linking effect was further confirmed by the thermogravimetric analysis (TGA). The effect of salts, such as NaCl and KCl on the binding capacity of the molecularly imprinted polymer was also discussed. Further, the rat serum and bile samples were applied and the binding of the MIPs for bilirubin was thus confirmed.

Towards the design of highly selective recognition sites into molecular imprinting polymers: A computational approach

A computational approach to simulate the formation of possible imprinted polymers in acetonitrile solution for theophylline (THO) is proposed, using combined molecular dynamics (MD), molecular mechanics (MM), docking and site mapping computational techniques. Methacrylic acid (MAA) and methylmethacrylate (MMA) monomers are used to simulate possible homo and copolymer structures. The model is able predict binding affinity and selectivity when considering THO analogues, such as caffeine, theobromine, xanthine and 3-methylxanthine. Comparison with available experimental data is proposed.

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.