Artificial antibodies to corticosteroids prepared by molecular imprinting

A catalytically active molecularly imprinted polymer that mimics peroxidase based on hemin: application to the determination of p-aminophenol

Despite the increasing number of applications of molecularly imprinted polymers (MIP) in analytical chemistry, the synthesis of polymers with hemin introduced as the catalytic center to mimic the active site of peroxidase remains as a challenge. In the current work, a new type of molecularly imprinted polymer (MIP) was synthesized with 4-aminophenol (4-APh) as the template and two monomers: hemin, which acts as the catalytic center, and methacrylic acid (MAA), which is used to build the active sites. This work shows that MIP successfully mimics peroxidase. For this purpose, a flow injection analysis system coupled to an amperometric detector was investigated through multivariate analysis. The determination of 4-APh was not affected by the equimolar presence of structurally similar phenol compounds, including catechol, 4-chloro-3-methylphenol, 2-aminophenol, guaiachol, chloroguaiachol and 2-cresol, thus highlighting the good performance of the imprinted polymer. Under the optimized experimental conditions, an analytical curve covering a wide linear response range from 0.8 up to 500 micromol L(-1) (r > 0.999) was obtained, and the method gave satisfactory precisions (n = 8), as evaluated via the relative standard deviation (RSD), of 4.1 and 3.2% for solutions of 4-APh of 50 and 500 micromol L(-1), respectively. Recoveries of 96-111% from water samples (tap water and river water) spiked with 4-APh were achieved, thus illustrating the accuracy of the proposed system.

Preparation of ion-imprinted silica gels functionalized with glycine, diglycine, and triglycine and their adsorption properties for copper ions

We report a new procedure for modifying the surface of silica gels with glycine, diglycine, and triglycine in the presence of copper ions to create a new type of copper-imprinted sorbent, which exhibits a high adsorption capacity and selectivity for copper ions. Our results show that copper adsorbed onto the copper-imprinted silica gel is 50% higher than that on nonimprinted silica gel at pH 4.5. The high adsorption capacity observed for the copper-imprinted silica gel is attributed to the stable copper complexes formed with two adjacent glycine, diglycine, or triglycine molecules with proper intermolecular distances obtained from the ion-imprinting procedure. Another possible reason for the high adsorption capacity is that the ion-imprinting procedure prevents the surface from being overcrowded; therefore, copper ions can form very stable 1:1 complexes with immobilized diglycine or triglycine. Interestingly, the imprinting effect is even more pronounced when the adsorption experiments are conducted in the presence of competing metal ions such as magnesium and calcium. The copper-imprinted silica gel exhibits a higher adsorption capacity than does the nonimprinted silica gel for all pH values, even when the concentrations of magnesium and calcium are 50 and 76 times higher than the concentration of copper.

Small organic molecular imprinted materials: their preparation and application

Molecular imprinting is a technique for preparing polymeric materials that are capable of recognizing and binding the desired molecular target with a high affinity and selectivity. The materials can be applied to a wide range of target molecules, even those for which no natural binder exists or whose antibodies are difficult to raise. The imprinting of small organic molecules (e.g., pharmaceuticals, pesticides, amino acids, steroids, and sugars) is now almost routine. In this review, we pay special attention to the synthesis and application of molecular imprinted polymer (MIPs) imprinted with small organic molecules, including herbicides, pesticides, and drugs. The advantages, applications, and recent developments in small organic molecular imprinted technology are highlighted.

Uniform molecularly imprinted microspheres and nanoparticles prepared by precipitation polymerization: the control of particle size suitable for different analytical applications

Molecularly imprinted polymers (MIPs) are being increasingly used as selective adsorbents in different analytical applications. To satisfy the different application purposes, MIPs with well controlled physical forms in different size ranges are highly desirable. For examples, MIP nanoparticles are very suitable to be used to develop binding assays and for microfluidic separations, whereas MIP beads with diameter of 1.5-3 microm can be more appropriate to use in new analytical liquid chromatography systems. Previous studies have demonstrated that imprinted microspheres and nanoparticles can be synthesized using a simple precipitation polymerization method. Despite that the synthetic method is straightforward, the final particle size obtained has been difficult to adjust for a given template. In this work, we initiated to study new synthetic conditions to obtain MIP beads with controllable size in the nano- to micro-meter range, using racemic propranolol as a model template. Varying the composition of the cross-linking monomer allowed the particle size of the MIP beads to be altered in the range of 130 nm to 2.4 microm, whereas the favorable binding property of the imprinted beads remained intact. The chiral recognition sites were further characterized with equilibrium binding analysis using tritium-labeled (S)-propranolol as a tracer. In general, the imprinted sites displayed a high chiral selectivity: the apparent affinity of the (S)-imprinted sites for (S)-propranolol was 20 times that of for (R)-propranolol. Compared to previously reported irregular particles, the chiral selectivity of competitive radioligand binding assays developed from the present imprinted beads has been increased by six to seven folds in an optimized aqueous solvent.

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.

Considerations for non-invasive in-flight monitoring of astronaut immune status with potential use of MEMS and NEMS devices

The dynamics of how astronauts' immune systems respond to space flight have been studied extensively, but the complex process has not to date been thoroughly characterized, nor have the underlying principles of what causes the immune system to change in microgravity been fully determined. Statistically significant results regarding overall immunological effects in space have not yet been established due to the relatively limited amount of experimental data available, and are further complicated by the findings not showing systematically reproducible trends. Collecting in vivo data during flight without affecting the system being measured would increase understanding of the immune response process. The aims of this paper are to briefly review the current knowledge regarding how the immune system is altered in space flight; to present a group of candidate biomarkers that could be useful for in-flight monitoring and give an overview of the current methods used to measure these markers; and finally, to further establish the need and usefulness of incorporating real-time analytical techniques for in-flight assessment of astronaut health, emphasizing the potential application of MEMS/NEMS devices.

Molecularly imprinted micro and nanospheres for the selective recognition of 17beta-estradiol

A one-step precipitation polymerization procedure for the synthesis of molecularly imprinted polymers selective for 17beta-estradiol yielding imprinted micro and nanospheres was developed in this study and compared to templated materials obtained by conventional bulk polymerization. The polymer particles prepared by precipitation polymerization exhibited a regular spherical shape at the micro and nanoscale with a high degree of monodispersity. Moreover, the influence of the polymerization temperature, and the ratio of functional monomer to cross-linker on the size of the obtained particles was investigated. The selectivity of the imprinted micro and nanospheres was evaluated by HPLC analysis and via radioligand binding assays. HPLC separation experiments revealed that the imprinted microspheres provide higher or similar affinity to the template in contrast to imprinted polymers prepared by conventional bulk polymerization or synthesized by multi-step swelling/polymerization methods. The dimensions of the imprinted nanospheres facilitate suspension in solution rendering them ideal for binding assay applications. Results from saturation and displacement assays prove that the imprinted nanospheres exhibit superior specific affinity to the target molecule in contrast to control materials. The binding properties of the nanospheres including binding isotherms and affinity distribution were studied via Freundlich isotherm affinity distribution (FIAD) analysis. Moreover, release experiments show that 70% of rebound 17beta-estradiol was released from the imprinted nanospheres within the first 2 h, while more intimately bound 17beta-estradiol molecules (approx. 16%) were released in the following 42 h. Fitting Brunnauer-Emmet-Teller (BET) multi-point adsorption isotherms to the obtained results indicated that the micro and nanospheres are characterized by a comparatively homogenous and narrow distribution of mesopores in contrast to the corresponding bulk polymers.

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.

Chitosan beads as molecularly imprinted polymer matrix for selective separation of proteins

Two kinds of molecularly imprinted polymers were prepared using hemoglobin as the imprinting molecule, acrylamide as the functional monomer, chitosan beads and maleic anhydride-modified chitosan beads as matrixes, respectively. Static adsorbing experimental results showed that an equal class of adsorption was formed in the imprinted polymers and the adsorption equilibrium constant and the maximum adsorption capacity were evaluated. Chromatographic characteristics showed that the column bedded with the hemoglobin imprinted beads could separate hemoglobin and bovine serum albumin effectively from their mixture, which indicates that the imprinted beads have very higher selectivity for hemoglobin than the non-imprinted with the same chemical composition.

The molecular reaction vessels for a transesterification process created by molecular imprinting technique

A polymeric catalyst was synthesized by co-polymerizing 4(5)-vinylimidazole and itaconic acid with trimethylpropanol trimethacrylate micro spheres. The catalyst obtained catalysed the transesterification process between p-nitrophenyl acetate and hexanol with maximal initial velocity(nu(max)) of 4.73 +/- 0.47 microM min(-1) mg(-1), and turnover rate (k(cat)) of 8.67 min(-1). Using p-nitrophenyl acetate as template, molecular imprinting process enhanced the nu(max) of the polymeric catalyst 3-fold. Each imprinted site can be considered as a single molecular reaction vessel, and achieved a k(cat) of 169 min(-1) towards the conversion of p-nitrophenyl acetate in hexanol.

Use of molecule imprinting-chemiluminescence method for the determination of tamoxifen in breast cancer sufferers' urine

The reaction between soluble Mn(IV) and tamoxifen can produce chemiluminescence and formaldehyde can enhance this chemiluminescence reaction. A tamoxifen molecular imprinted polymer (MIP) was synthesized and its adsorption selectivity to tamoxifen in aqueous solution was evaluated. Using a synthesized tamoxifen MIP as the recognition material and a soluble Mn(IV)-formaldehyde-tamoxifen chemiluminesence system as the detection system, a new molecule imprinting-chemiluminesence method of determination of tamoxifen was established. The response range of this method was 1.0 x 10(-7)-6.0 x 10(-6) g/mL, with a linear correlation coefficient of 0.997. The detection limit was 4 x 10(-8) g/mL. The relative standard deviation for 5.0 x 10(-7) g/mL tamoxifen solution was 4.1% (n = 9).

Acrylic polymeric nanospheres for the release and recognition of molecules of clinical interest

Cross-linked poly(methylmethacrylate-co-methacrylic acid) nanospheres were imprinted with theophylline through template radical polymerisation in diluted acetonitrile solution. This study will focus on the effect of functional monomer nature used (methylmethacrylate and/or methacrylic acid) in the recognition and in the release of template in order to develop a material with combined properties of drug delivery and rebinding for clinical applications. After template extraction the nanospheres showed satisfactory recognition properties (up to 1mg template/g of polymer). Moreover polymers prepared selectively removed theophylline with a theophylline rebinding of 5.1 times higher than that of caffeine, a compound of similar structure. Drug release properties were also satisfactory (up to 95% of loaded theophylline in 7 days).

Molecular imprinting: a dynamic technique for diverse applications in analytical chemistry

Continuous advances in analyzing complex matrices, improving reliability and simplicity, and performing multiple simultaneous assays with extreme sensitivity are increasing. Several techniques have been developed for the quantitative assays of analytes at low concentrations (e.g., high-pressure liquid chromatography, gas chromatography, immunoassay and the polymerase chain reaction technique). To achieve highly specific and sensitive analysis, high affinity, stable, and specific recognition agents are needed. Although biological recognition agents are very specific and sensitive they are labile and/or have a low density of binding sites. During the past decade molecular imprinting has emerged as an attractive and highly accepted tool for the development of artificial recognition agents. Molecular imprinting is achieved by the interaction, either noncovalent or covalent, between complementary groups in a template molecule and functional monomer units through polymerization or polycondensation. These molecularly imprinted polymers have been widely employed for diverse applications (e.g., in chromatographic separation, drug screening, chemosensors, catalysis, immunoassays etc.) owing to their specificity towards the target molecules and high stability against physicochemical perturbations. In this review the advantages, applications, and recent developments in molecular imprinting technology are highlighted.

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.

Selective separation of active inhibitors of epidermal growth factor receptor from Caragana jubata by molecularly imprinted solid-phase extraction

A feasibility research was performed to study the possibilities of using a molecularly imprinted polymer as sorbent material in solid-phase extraction for the separation of active inhibitors of epidermal growth factor receptor (EGRF) from Caragana Jubata, a Chinese traditional Tibetan medicine. A molecularly imprinted polymer using quercetin, an active anti-EGFR inhibitor (IC50 = 15 microM), as the template and acrylamide as the functional monomer was prepared. The polymer was evaluated as a selective sorbent in molecularly imprinted solid-phase extraction. The EtOAc extract of Caragana Jubata was loaded on the polymer, and two novel active anti-EGFR inhibitors were found to be selectively retained after washing the polymer with appropriate solvent to disrupt the non-specific interactions occurring between the sample and the polymer matrix, which were identified as (E)-piceatannol (IC50 =4.9 microM) and butein (IC50 = 10 microM). The present work affords us a new potential method for selective separation of bioactive components from herb by using molecularly imprinted polymer as a solid-phase extraction adsorbent.

Cross-linked dendrimer hosts containing reporter groups for amine guests

The integration of a chromogenic reporter group into the recently reported (Zimmerman, S. C.; Wendland, M. S.; Rakow, N. A.; Zharov, I.; Suslick, K. S. Nature 2002, 418, 399-403) monomolecular imprinting approach is described. The resulting highly cross-linked, macromolecular hosts show rapid, selective, high affinity, two-point binding of straight-chain diamine guests. Over longer times, the hosts are more promiscuous, binding a broader range of diamines. A rigorous test of imprinting was performed wherein the cross-reactivities of two dendrimers derived from different templates are compared. The test reveals a guest-dependent kinetic binding effect masquerading as evidence of a highly selective two-point imprinting process.

Removal of the fermentation by-product succinylL-tyrosine from the ?-lactamase inhibitor clavulanic acid using a molecularly imprinted polymer

Clavulanic acid is a beta-lactamase inhibitor used in therapeutic combinations with the penicillin-type antibiotics. During the fermentation leading to clavulanic acid, a succinyl L-tyrosine by-product is unavoidably formed. Occasionally, the amount of this by-product is found to be as high as 2% of the product even after standard purification operations. To further remove this impurity, we prepared a highly specific adsorbent for succinyl L-tyrosine with the molecular imprinting technique. This was performed by simultaneously using vinylbenzyl trimethylammonium chloride and methacrylic acid as the functional monomers. The imprinted polymer selectively bound succinyl L-tyrosine, and could be successfully used to remove this impurity at concentrations of less than 2% in the presence of clavulanic acid.

Separation and detection of neuroactive steroids from biological matrices

This review is based on a selection of research papers published mainly in the last decade and it describes various analytical aspects of separation and detection of neuroactive steroids in biological matrices.

The use of high pressure for separation and production of bioactive molecules

Due to its action on the forces governing inter- and intramolecular interactions, the application of high pressure to biopurification or bio-elaboration of a product are of interest. The two closely thermodynamically related parameters, pressure and temperature, render processes based on their action clean, as no chemical reagents have to be added (and thus further removed) when they are applied. The use of high pressure in the development of desorption methods for the purification of bioactive molecules, particularly in the immunoaffinity field, is reviewed and discussed. Also mentioned is the application of the pressure parameter during the synthesis of a bioreagent. Finally, integrated processes relative to the synthesis and purification of these compounds are proposed.

Scintillation proximity assay using molecularly imprinted microspheres

Molecularly imprinted microspheres were prepared as antibody binding mimics and used in scintillation proximity assay of a beta-adrenergic antagonist, (S)-propranolol. By using small polymer beads, we were able to place an organic scintillator and an "antenna" component in close proximity to the imprinted binding sites. When the radioactive template bound to the polymer, radiation energy was effectively transferred, via the antenna component, to the scintillator to generate a fluorescence signal. Using molecularly imprinted microspheres instead of antibodies, we have demonstrated competitive scintillation proximity assays for (S)-propranolol in both organic and aqueous solvents. The experimental results were further validated by normal ligand binding analysis, where liquid scintillation counting was used for quantification.

Fibers coated with molecularly imprinted polymers for solid-phase microextraction

The simplicity and flexibility of solid-phase microextraction have been combined with the selectivity of molecularly imprinted polymers (MIPs). Silica fibers were coated reproducible with a 75-microm layer of methacrylate polymer either nonimprinted or imprinted with clenbuterol to compare their extraction characteristics under various conditions. Although the template molecule could be removed effectively from the imprinted polymer, structural analogues of clenbuterol were used for evaluation. The influence of pH on the extractability of brombuterol was investigated. Extraction yields up to approximately 80% were obtained when both types of fibers were used to extract brombuterol from phosphate buffer (pH 7.0). In contrast, yields of about 75 and <5% were obtained when extraction was performed from acetonitrile with imprinted and nonimprinted polymers, respectively, which demonstrates the selectivity of the MIP-coated fiber. Time sorption profiles were measured for the extraction of brombuterol from buffer and acetonitrile at the 10 and 100 ng/mL level with both types of fibers in order to compare extraction characteristics. Equilibrium times of about 30 and 90 min were found for the extraction of brombuterol from acetonitrile and buffer, respectively. The MIP-coated fibers were capable of extracting five structural analogues of clenbuterol from both buffer and acetonitrile, which suggests that the amine alcohol part of these molecules is responsible for interaction with the imprinted polymer. To achieve selective extraction of brombuterol from human urine, MIP-coated fibers were washed with acetonitrile after the extraction. Clean extracts and yields of approximately 45% were obtained, demonstrating the suitability of MIP-coated fibers for the analysis of biological samples.

Molecular imprinting: at the edge of the third millennium

Molecularly imprinted polymers (MIPs) represent a new class of materials that have artificially created receptor structures (1-3). Since their discovery in 1972, MIPs have attracted considerable interest from scientists and engineers involved with the development of chromatographic adsorbents, membranes, sensors and enzyme and receptor mimics.