Probing the molecular basis for ligand-selective recognition in molecularly imprinted polymers selective for the local anaesthetic bupivacaine

Molecularly imprinted polymers (MIPs) are an interesting novel class of sor bent for analytical separation science, with one particular area of potenti al being in the development of highly selective solid-phase extraction syst ems. In order to optimise polymer-ligand selectivity and to examine the und erlying physical mechanisms, polymers with selectivity for the local anaest hetic bupivacaine have been synthesised and their ligand-recognition charac teristics examined. The influence of rebinding media parameters (pH, ionic strength, polarity) have been studied and optimised with respect to selecti ve MIP-ligand binding, and the working range of the polymers with respect t o these parameters has been mapped. These results highlight the robustness of MIPs and the breadth of potential assay conditions that may be employed. Finally, competitive binding studies using the closely related structures mepivacaine, ethycaine, ropivacaine and pentycaine in solvent mixtures of d ifferent polarity revealed that the entropy-driven hydrophobic effect is si gnificant in polar solvents, whereas enthalpy-driven electrostatic interact ions dominate in non-polar media. (C) 2001 Elsevier Science B.V. All. right s reserved.