Modification of platinum microelectrode with molecularly imprinted over-oxidized polypyrrole for dopamine measurement in rat striatum

A highly sensitive and selective electrochemical microelectrode using the molecularly imprinted (MIP) electropolymer of over-oxidized polypyrrole (OPPy) was proposed for in vivo detection of dopamine (DA) which process is different from current approaches for in vitro DA detection using MIP-based macroelectrode. The proposed MIP electrosynthesized by our present method under a DA/pyrrole-monomer concentration ratio of 1 mM/10 mM yielded the best results for DA adsorption, reaching 2.6-fold that of similar microelectrodes without imprinting. Differential normal pulse voltammetry techniques was used to evaluate the DA-imprinted OPPy microelectrodes for demonstrating high selectivity for in vitro DA detection under conditions with various competitive electroactive molecules. The validity of the modified OPPy-MIP thin-film microelectrodes was further verified with amperometric i-t measurements, which showed a lower DA levels of detection (10-100 nM) and the low detection limit of 4.5 nM with signal to noise ratio of 3. Good reproducibility with relative standard deviation of 5.45% and long-term stability within two weeks were also observed. The developed OPPy-MIP microelectrode has been successfully applied for acute in vivo DA detection in the striatum of anesthetized rats with 3,4-dihydroxy-l-phenylalanine (l-DOPA) administration, which can be used for future evaluation of novel therapeutic treatments in Parkinsonian rats.