MIP sensor made using multi-current step electro-polymerization method on framed Ag-SPE for glutamic acid enantiomer recognition

A molecularly imprinted, polypyrrole based, sensor with significant enantioselective recognition ability for D- and L- glutamic acids was prepared using a multi-current steps technique on framed silver screened printed electrodes (Ag-SPE). The surfaces of the silver nanoparticles were passivated to obtain a dense, thick MIP film, which was able to inhibit the dissolution of Ag-SPE during the potentiostatic monomer electropolymerization at high positive applied potentials. After template removal, a pretreatment step was carried out at 10 V (vs. Ag/AgCl) to induce template binding and bring about the oxidative dissolution of printed silver particles on the SPE. From the i-t curves, application of the break-down current was found to be needed for only a shorter time for the template-free solution, while no such breakdown was found for the test solution containing the template molecule, implying that the MIP film provided a high resistance that inhibited Ag-SPE dissolution. After pretreatment for 600 s, the optimum selectivities for D- and l-glutamine on their template imprinted films were L/D = (145.9 ± 17.3)/1 and D/L = (126.0 ± 15.4)/1 respectively, based on the current change between 0 and 2 V (vs. Ag/AgCl) with the two enantiomers being present at the same concentration (10 mM). The imprinted glutamic acid films were characterized using scanning electron microscopy with energy dispersive spectroscopy. A recognition mechanism, related to the dissolution of Ag-SPE in the pretreatment step at positive potentials is also proposed.