Molecularly imprinted electrochemical sensor able to enantroselectivly recognize D and L-tyrosine

Electrochemical sensors were fabricated on nickel electrodes by molecularly imprinting D and L-tyrosine on polypyrrole films to form complementary cavities for subsequent template recognition. The performance of the imprinted films was evaluated by coulometry using an applied positive potential to induce adsorption of the target molecules. Using this procedure high enantioselectivities was found for each imprinted film. The individual selectivities for L and D-tyrosine on their respective imprinted films were estimated to be L/D = 9.4/1 and D/L = 27.2/1, determined by applying potential at a sweep rate of 0. 1 V/s from -0.1 to 0.5 V (versus Ag/AgCl) with the two enantiomers being present at the same concentration (5 mM). Several factors affecting rebinding, such as extraction time, film thickness, template concentration and sweep rate were investigated to achieve optimum recognition ability. The diffusion of target molecules in the polypyrrole films was also examined. A recognition mechanism for the interaction of the polypyrrole film for its template under the influence of an applied positive potential is proposed in this study. (c) 2005 Elsevier B.V. All rights reserved.