The area of biomimetic catalysis based on molecular imprinted polymers has progressed considerably over the last two decades, with research efforts focused on developing catalysts for challenging reactions and on understanding the key factors in template structure and polymer morphology that influence efficiency and selectivity. Recent advances and significant achievements in the field presented in this chapter are organized according to four topics: hydrolytic reactions of challenging substrates, oxidase mimics, metallo-enzyme mimics, and polymers that display unusual reactivity, such as in the case of reactions for which enzymes don't exist, such as Diels-Alder and Kemp elimination. For each theme, significant examples for recent literature are presented and discussed.
A signalling molecularly imprinted polymer was synthesised for easy detection of tamoxifen and its metabolites. 6-Vinylcoumarin-4-carboxylic acid (VCC) was synthesised from 4-bromophenol to give a fluorescent monomer, designed to switch off upon binding of tamoxifen. Clomiphene, a chlorinated analogue, was used as the template for the imprinting, and its ability to quench the coumarin fluorescence when used in a 1:1 ratio was demonstrated. Tamoxifen and 4-hydroxytamoxifen were also shown to quench coumarin fluorescence. Imprinted and non-imprinted polymers were synthesised using VCC, methacrylic acid as a backbone monomer and ethylene glycol dimethacrylate as cross-linker, and were ground and sieved to particle sizes ranging between 45 and 25 μm. Rebinding experiments demonstrate that the imprinted polymer shows very strong affinity for both clomiphene and tamoxifen, while the non-imprinted polymer shows negligible rebinding. The fluorescence of the imprinted polymer is quenched by clomiphene, tamoxifen and 4-hydroxytamoxifen. The switch off in fluorescence of the imprinted polymer under these conditions could also be detected under a UV lamp with the naked eye, making this matrix suitable for applications when coupled with a sample preparation system.
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