Elena V. Piletska

Recognition of ephedrine enantiomers by molecularly imprinted polymers designed using a computational approach

A new approach to the computational design of molecularly imprinted polymers (MIP) specific for ephedrine is presented. A virtual library of functional monomers was developed and screened against the template using molecular modelling software. The monomers giving the highest binding score were co-polymerized with a cross-linker in the presence of ephedrine. Control (blank) polymers were prepared under the same conditions but in the absence of the template. A good correlation was found between the modelling results and performance of the materials in an HPLC study. A MIP based on one of the selected monomers—hydroxyethyl methacrylate—gave a separation of ephedrine enantiomers with a separation factor α of 1.42–2.09 (depending on temperature). This figure is larger than the α values generally obtained with commercially available chiral phases. It is anticipated that the computational approach will be of use for the rational design of MIPs and the prediction of polymer affinity and specificity.

Substitution of Antibodies and Receptors with Molecularly Imprinted Polymers in Enzyme-Linked and Fluorescent Assays

A new technique for coating microtitre plates with molecularly imprinted polymers (MIP), specific for low-molecular weight analytes (epinephrine, atrazine) and proteins is presented. Oxidative polymerization was performed in the presence of template; monomers: 3-aminophenylboronic acid (APBA), 3-thiopheneboronic acid (TBA) and aniline were polymerized in water and the polymers were grafted onto the polystyrene surface of the microplates. It was found that this process results in the creation of synthetic materials with antibody-like binding properties. It was shown that the MIP-coated microplates are particularly useful for assay development. The high stability of the polymers and good reproducibility of the measurements make MIP coating an attractive alternative to conventional antibodies or receptors used in enzyme linked immunosorbent assay (ELISA).

Direct replacement of antibodies with molecularly imprinted polymer nanoparticles in ELISA--development of a novel assay for vancomycin.

A simple and straightforward technique for coating microplate wells with molecularly imprinted polymer nanoparticles (nanoMIPs) to develop assays similar to the enzyme-linked immunosorbent assay (ELISA) is presented here for the first time. NanoMIPs were synthesized by a solid-phase approach with an immobilized vancomycin (template) and characterized using Biacore 3000, dynamic light scattering, and electron microscopy. Immobilization, blocking, and washing conditions were optimized in microplate format. The detection of vancomycin was achieved in competitive binding experiments with a horseradish peroxidase-vancomycin conjugate. The assay was capable of measuring vancomycin in buffer and in blood plasma within the range of 0.001-70 nM with a detection limit of 0.0025 nM (2.5 pM). The sensitivity of the assay was 3 orders of magnitude better than a previously described ELISA based on antibodies. In these experiments, nanoMIPs have shown high affinity and minimal interference from blood plasma components. Immobilized nanoMIPs were stored for 1 month at room temperature without any detrimental effects to their binding properties. The high affinity of nanoMIPs and the lack of a requirement for cold chain logistics make them an attractive alternative to traditional antibodies used in ELISA.

Selection of imprinted nanoparticles by affinity chromatography

Soluble molecularly imprinted nanoparticles were synthesised via iniferter initiated polymerisation and separated by size via gel permeation chromatography. Subsequent fractionation of these particles by affinity chromatography allowed the separation of high affinity fractions from the mixture of nanoparticles. Fractions selected this way possess affinity similar to that of natural antibodies (K(d) 6.6x10(-8)) M and were also able to discriminate between related functional analogues of the template.

Rational design and synthesis of water-compatible molecularly imprinted polymers for selective solid phase extraction of amiodarone

Novel water-compatible molecularly imprinted polymers (MIPs) selective for amiodarone (AD) were designed via a new methodology which relies on screening library of non-imprinted polymers (NIPs). The NIP library consisted of eighteen cross-linked co-polymers synthesized from monomers commonly used in molecular imprinting. The binding capacity of each polymer in the library was analyzed in two different solvents. Binding in water was used to assess non-specific (hydrophobic) interactions and binding in an appropriate organic solvent was used to assess specific interactions. A good correlation was found between the screening tests and modeling of monomer-template interactions performed using computational approach. Additionally, analysis of template-monomer interactions was performed using UV-vis spectroscopy. As the result, 4-vinylpyridine (4-VP) was selected as the best monomer for developing MIP for AD. The 4-VP-based polymers demonstrated imprinting factor equal 3.9. The polymers performance in SPE was evaluated using AD and its structural analogues. The recovery of AD was as high as 96% when extracted from spiked phosphate buffer (pH 4.5) solution and 82.1% from spiked serum samples. The developed MIP shown as a material with specific binding to AD, comparing to its structural analogues, 1-(2-diethylaminoethoxy)-2,6-diiodo-4-nitrobenzene and lidocaine, which shown 9.9% and 25.4% of recovery from the buffer solution, correspondingly. We believe that the screening of NIP library could be proposed as an alternative to commonly used computational and combinatorial approaches.

Biotin-specific synthetic receptors prepared using molecular imprinting

The composition of new molecularly imprinted polymers (MIPs) specific for biotin was optimised using molecular modelling software. Three functional monomers: methacrylic acid (MAA), 2-(trifluoromet ...

Cubic Molecularly Imprinted Polymer Nanoparticles with a Fluorescent Core

Molecular recognition is a fundamental process for all living systems. Applications of the phenomenon have exploited antibodies as the selective components of immunoassays, affinity phases and biosensors and as therapeutic agents. Molecularly imprinted polymers (MIPs) are one of the leading contenders for alternatives to antibodies. MIPs generally are cross-linked polymers synthesized in the presence of the target compound (the template). After the removal of the template, cavities with complementary size and shape to the template are created, which can recognize and selectively rebind the template. MIPs have been successfully applied to solid-phase extraction and in biosensors. The synthesis of MIPs with architectures which are well defined on the molecular level is a future priority. MIP nanoparticles (NPs) can be prepared by a number of methods. Each of these have some disadvantages including: production of particles with irregular shapes and sizes, heterogeneous binding sites, decreased affinity due to use of surfactants and high polymerization temperatures, long polymerization time, relatively low yield, etc. Here, we have developed a new core–shell approach. In order to detect binding, fluorescence is a promising technique, since fluorescent labeling can be a powerful tool for probing the local environment, as well as for biological imaging. As a site for placement of a fluorescent label, the NP core is a promising location, since it is isolated from the bulk solution by the surrounding polymer shell. There are currently two reported approaches for the incorporation of fluorescent species in the core of MIP NPs. One example involved the creation of a MIP layer over inorganic quantum dots. In the second case two layers were created over silicacoated magnetic particles; the first consisting of a fluorescently labeled polymer and the second, outer layer, was the MIP. In our approach dendrimers were selected as the core from which to graft a MIP shell to form imprinted NPs. Dendrimers are biocompatible, soluble macromolecules possessing highly defined regularly branched structures, a well defined shape, size and number of peripheral functionalities. Using dendrimers as the core in a controlled or “living” polymerization would ensure precise grafting at the molecular level. An earlier example of dendrimer-based MIP NPs was reported by Zimmerman. The monomolecular imprinted NPs formed had only one binding site at the centre of the particles and involved a long and tedious synthesis. The use of dendrimer-based macroinitiators for the synthesis of NPs using atom transfer living radical, nitroxide-initiated and microemulsion polymerizations have been reported. Unfortunately the synthesis conditions are mostly incompatible with the imprinting process (high temperature, presence of ions, etc.). Much more favorable conditions would be associated with use of iniferters (initiator, chain transfer agent, terminator). Here we describe the synthesis of NPs in solution without the use of surfactant and no requirement for high temperatures in 120 s polymerization time. The NPs are dispersible in both aqueous and organic solvents. A unique, versatile and highly controlled technique combining dendrimer-based macroiniferters, living polymerization, nanotechnology, molecular imprinting and novel fluorescent sensing technique is demonstrated. In order to first characterize the properties of dendrimercore NPs, a non-fluorescent core was used. Iniferter units were attached on the periphery of polyamidoamine (PAMAM) dendrimers, generation 4, creating a soluble macroiniferter. This was used as core for the synthesis of NPs (Scheme 1). As iniferter S-(carboxypropyl)-N,N-diethyldithiocarbamic acid (CNDDA) was used and coupled to the peripheral primary amino groups of the dendrimers (Supporting Information). The polymerization was initiated simultaneously from potentially 48 points per dendrimer moiety. Dendrimer-core MIP-shell NPs were synthesized in just two minutes by UV irradiation. The use of UV-initiated living radical polymerization, besides imparting better control over the size distribution, has another fundamental advantage. The polymerization process can be re-initiated by UV exposure, where the already synthesized NPs will act as a macroinitiator, allowing many possibilities for further modification of the particle surface properties. [*] P. K. Ivanova-Mitseva, Dr. A. Guerreiro, Dr. E. V. Piletska, Dr. M. J. Whitcombe, Dr. F. Davis, Prof. S. A. Piletsky Cranfield Health, Vincent Building, Cranfield University Cranfield, MK43 0AL (UK) E-mail: m.whitcombe@cranfield.ac.uk

Computational and experimental investigation of molecular imprinted polymers for selective extraction of dimethoate and its metabolite omethoate from olive oil.

This work presents the development of molecularly imprinted polymers (MIPs) for the selective extraction of dimethoate from olive oil. Computational simulations allowed selecting itaconic acid as the monomer showing the highest affinity towards dimethoate. Experimental validation confirmed modelling predictions and showed that the polymer based on IA as functional monomer and omethoate as template molecule displays the highest selectivity for the structurally similar pesticides dimethoate, omethoate and monocrotophos. Molecularly imprinted solid phase extraction (MISPE) method was developed and applied to the clean-up of olive oil extracts. It was found that the most suitable solvents for loading, washing and elution step were respectively hexane, hexane-dichloromethane (85:15%) and methanol. The developed MIPSE was successfully applied to extraction of dimethoate from olive oil, with recovery rates up to 94%. The limits of detection and quantification of the described method were respectively 0.012 and 0.05 μg g(-1).

“Bite‐and‐Switch” Approach to Creatine Recognition by Use of Molecularly Imprinted Polymers

The detection of creatine is important in the analysis of athletes and body builders. Here is reported the preparation of a synthetic polymer using imprinting polymerization, which leaves the polym ...

Preliminary evaluation of new polymer matrix for solid-phase extraction of nonylphenol from water samples.

Molecularly imprinted (MIP) and blank polymers with affinity for nonylphenol were designed using computational modelling. Chromatographic tests demonstrated higher affinity of imprinted polymers towards the template nonylphenol as compared with blank polymers. The performance of both polymers in solid-phase extraction was however very similar. Both blank and imprinted polymers appeared to be suitable for the removal and pre-concentration of nonylphenol from contaminated water samples with 99% efficiency of the recovery. The commercial resins PH(EC) (Biotage) and C18 (Varian) tested in the same conditions used for comparative purposes had recovery rate <84%. The polymer capacity for nonylphenol was 231 mg g(-1) for blank and 228 mg g(-1) for MIP. The synthesised materials can have significance for sample pre-concentration and environmental analysis of this class of compounds.