S A Piletsky

Receptor and transport properties of imprinted polymer membranes – a review

Abstract Over the last 10 years new types of polymeric materials with molecular recognition sites for low-weight organic substances have been prepared using the molecular imprinting approach. In this review paper, in particular, the recognition and transport properties of molecularly imprinted polymer (MIP) membranes prepared thus far are summarized and analyzed. Microporous and macroporous MIP membranes show the same receptor but largely different transport properties. The nature of selectivity of microporous MIP membranes is discussed and a descriptive model for transport selectivity via specific “gates” is developed. The high specificity and stability of MIPs render them as promising alternatives to enzymes, antibodies, and other natural receptors usually used in affinity chromatography and sensor technology. The application potential of MIP membranes, especially for affinity separations, membrane chromatography and membrane sensors, is outlined. Conclusions about the possibilities to improve their performance are presented. In general, these investigations open a way to the design of supramolecular devices that could perform highly selective functions such as recognition, transformation, transfer, regulation and allow signal and information processing.

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.

MIP-based solid phase extraction cartridges combined with MIP-based sensors for the detection of microcystin-LR.

Microsystin-LR is one of the most widespread and dangerous toxins produced by the freshwater Cyanobacteria. The contamination of water supplies with microcystin-LR has been reported in several areas around the world and the development of an easy-to-use, rapid, robust and inexpensive sensor for this toxin is urgently required. In this work an artificial receptor for microcystin-LR was synthesised using the technique of molecular imprinting. The composition of the molecularly imprinted polymer (MIP) was optimised using computer modelling. The synthesised polymer was used both as a material for solid-phase extraction (SPE) and as a sensing element in a piezoelectric sensor. Using the combination of SPE followed by detection with a piezoelectric sensor the minimum detectable amount of toxin was 0.35 nM. The use of MIP-SPE provided up to 1000 fold pre-concentration, which was more than sufficient for achieving the required detection limit for microcystin-LR in drinking water (1 nM). This work is the first example where the same MIP receptor has been used successfully for both SPE and the corresponding sensor.

“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 ...

PREPARATION AND USE OF MEMBRANES WITH POTENTIAL-CONTROLLED FUNCTIONS

A new type of membrane with potential-controllable functions was prepared by grafting polyaniline to the surface of track-etch Nucleopore membrane with a vacuum deposited gold layer (PANI-membranes). Because of the cylindrical shape of these pores, a nanocylinder of the desired conducting material is obtained in each pore. A potential applied to PANI-membranes governs the properties of the conducting layer, such as charge and its distribution, conformation, and density and, hence, controls the diffusion rate of substances through these membranes. The variation in diffusion rates of different substances with different potentials applied to PANI-membranes provides the basis for the application of these membranes in separation processes and sensors.

Ice matrix in reconfigurable microfluidic systems

Microfluidic devices find many applications in biotechnologies. Here, we introduce a flexible and biocompatible microfluidic ice-based platform with tunable parameters and configuration of microfluidic patterns that can be changed multiple times during experiments. Freezing and melting of cavities, channels and complex relief structures created and maintained in the bulk of ice by continuous scanning of an infrared laser beam are used as a valve action in microfluidic systems. We demonstrate that pre-concentration of samples and transport of ions and dyes through the open channels created can be achieved in ice microfluidic patterns by IR laser-assisted zone melting. The proposed approach can be useful for performing separation and sensing processes in flexible reconfigurable microfluidic devices.

A reconfigurable microfluidic platform in ice

In this research a CO2 IR laser was used to create reconfigurable microchannels in ice where parameters could be changed during operation. The flow of liquid acts as its own shut-off valve by freezing/melting. Concentration of dye can be achieved in ice and was observed with a reflection spectrophotometer