Molecularly imprinted polymers as a selective sorbent for forensic applications in biological samples-a review

Molecularly imprinted polymers (MIP) consist of a molecular recognition technology with applicability in different areas, including forensic chemistry. Among the forensic applications, the use of MIP in biological fluid analysis has gained prominence. Biological fluids are complex samples that generally require a pre-treatment to eliminate interfering agents to improve the results of the analyses. In this review, we address the development of this molecular imprinting technology over the years, highlighting the forensic applications of molecularly imprinted polymers in biological sample preparation for analysis of stimulant drugs such as cocaine, amphetamines, and nicotine.

Uptake of nicotine from suspension culture of Nicotiana tabacum by molecularly imprinted polymers

OBJECTIVES

The aim was to use molecularly imprinted polymers (MIPs) for the selective recovery of nicotine in plant cell cultures. MIPs can selectively uptake nicotine from suspension cultures of N. tabacum, and therefore may be useful for improving levels of secondary metabolites in plant cell cultures.

METHODS

Suspension cultures of N. tabacum were initiated from callus and maintained in liquid Murashige and Skoog (MS) media containing 3% w/v sucrose, 0.1 mg/l alpha-naphthaleneacetic acid acid (NAA) and 0.25 mg/l kinetin. Tween 80 at 1% was used for permeabilisation of cell cultures. Pre-weighed XAD-2 and two types of synthesized polymers, MIPs (A and B with one and two functional monomers, respectively) and corresponding non-imprinted polymers (NIPs), A and B, were introduced aseptically into the permeabilised suspension cultures of N. tabacum, the nicotine contents of polymers were determined by gas chromatography and the adsorption yield of polymers were determined.

KEY FINDINGS

Cell cultures of N. tabacum accumulated nicotine alkaloid intracellularly in varying levels, 6.8-14.9 mg/l fresh weight. MIPs were able to uptake 50-70% of released nicotine in suspension cultures of N. tabacum, whereas XAD-2 recovered only 30-40%. The total levels of accumulated nicotine were enhanced up to 20 mg/l by simultaneous use of Tween 80 and MIPs.

CONCLUSIONS

The findings indicate the potential use of MIPs to uptake nicotine from suspension cultures of N. tabacum, and increase productivity of secondary metabolites in plant cell cultures.

Artificial receptors

Herein I will provide a brief overview of artificial receptors with emphasis on molecularly imprinted polymers (MIPs) and their applications. Alternative techniques to produce artificial receptors such as in silico designed and modelled polymers as well as different receptors designed using libraries of more or less natural composition will also be mentioned. Examples of these include aptamers and bio-nanocomposites. The physical presentation of the receptors is important and may depend on the application. Block polymerization of MIPs and grinding to particles of suitable size used to be the preferred technique, but today beaded materials can be produced in sizes down to nanobeads and also nanofibers can be used to increase available surface area and thereby capacity. For sensor applications it may be attractive to include the artificial receptors in surface coatings or in membrane structures. Different composite designs can be used to provide additional desirable properties. MIPs and other artificial receptors are gaining rapidly increasing attention in very shifting application areas and an attempt to provide a systematic account for current applications has been made with examples from separation, solid-phase extraction, analysis, carbohydrate specific experiments, and MIPs-directed synthesis.

Application of molecularly imprinted polymers to solid-phase extraction of analytes from real samples

A review is presented of recent developments in the use of molecularly imprinted polymers (MIPs) as selective materials for solid-phase extraction. Compared with traditional sorbents, MIPs can not only concentrate but also selectively separate the target analytes from real samples, which is crucial for the quantitatively determination of analytes in complex samples. Consequently, as one of the most effective sorbents, MIPs have been successfully applied to the pretreatment of analytes in foods, drugs, and biological and environmental samples in the past five years.

Uniformly-sized, molecularly imprinted polymers for nicotine by precipitation polymerization

Uniformly-sized, molecularly imprinted polymers (MIPs) for (S)-nicotine have been prepared by a precipitation polymerization method using methacrylic acid (MAA) or 2-(trifluoromethyl)acrylic acid (TFMAA) as a functional monomer and divinylbenzene (DVB) as a cross-linker in a mixture of toluene and acetonitrile. The (S)-nicotine-imprinted MAA-co-DVB polymers were monodispersed microspheres of about 4 microm in diameter, while the TFMAA-co-DVB ones were gel-like. Molecular recognition abilities of the former MIPs were evaluated for nicotine and its structurally related compounds in liquid chromatography using a mixture of sodium phosphate buffer and acetonitrile as the eluent. Enantioseparation of nicotine was attained using the (S)-nicotine-imprinted MAA-co-DVB polymers. Furthermore, they could selectively trap nicotine in cigarette smoke extracts.

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.

Optical interrogation of molecularly imprinted polymers and development of MIP sensors: a review

This article reviews the progress and developments achieved in the past five years (2000-2005) in the application of optical analytical techniques to the evaluation of molecularly imprinted polymer (MIP) characteristics. The MIP binding efficiency, recognition processes and selectivity have been intensively studied by optical means due to the general high sensitivity and simplicity of the utilisation of optical techniques. In addition, recent progress in the covalent linkage of MIPs to optical transducers has allowed for the realisation of highly efficient and robust optical MIP-based molecular recognition sensors. The review provides insight into the various approaches to the optical interrogation of MIPs, and is organised according to the type of optical technique employed (fluorescence, UV/Vis and infrared spectroscopy, surface plasmon resonance, chemiluminescence, refractive interference spectroscopy and Raman scattering) and the detailed strategies applied. The review also covers the recent progress achieved in the area of optical sensors based on MIPs.

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.

Nuclear magnetic resonance study of the molecular imprinting of (−)-nicotine: template self-association, a molecular basis for cooperative ligand binding

In the present study, the interactions of components in a (-)-nicotine molecular imprinting polymerization mixture have been studied by 1H NMR spectroscopy. The dissociation constants for complexation of template by a functional monomer analogue, acetic acid, have been determined. Nicotine was shown to self-associate at concentrations comparable to those used in previous molecular imprinting studies (app K(diss) = 0.082M in CDCl3 at 298 K). The extent of self-association was enhanced by the presence of acetic acid. Previous studies on (-)-nicotine-imprinted methacrylic acid-ethylene dimethacrylate co-polymers suggested the involvement of recognition sites for template-template complexes. Collectively these results provide the first direct evidence for the presence of template-template complexes, and support the previously hypothesized basis for cooperative ligand recognition events in this polymer system.