Direct electrochemistry and electrocatalysis of myoglobin on redox-active self-assembling monolayers derived from nitroaniline modified electrode / S. Ashok Kumar, Shen Ming Chen // Biosensors and Bioelectronics Vol. 22, Taiwan. -

Abstract

The adsorption processes and electrochemical behavior of 4-nitroaniline (4-NA) and 2-nitroaniline (2-NA) adsorbed onto glassy carbon electrodes (GCE) have been investigated in aqueous 0.1 M nitric acid (HNO3) electrolyte solutions using cyclic voltammetry (CV). Nitroaniline adsorbs onto GCE surfaces and upon potential cycling past -0.55 V is transformed into the arylhydroxylamine (ArHA), which exhibits a well-behaved pH dependent redox couple centered at 0.32 V (pH 1.5). This modified electrode can be readily used as an immobilization matrix to entrap proteins and enzymes. In our studies, myoglobin (Mb) was chosen as a model protein for investigation. A pair of well-defined reversible redox peaks for Mb(Fe(III)-Fe(II)) was obtained at the Mb/arylhydroxylamine modified glassy carbon electrode (Mb/HAGCE) by direct electron transfer between the protein and the GCE. The formal potential (E0′), the surface coverage (Γ) and the electron transfer rate constant (ks) were calculated as -0.317 V, 4.15 ± 0.5 × 10-11 mol/cm2 and 51 ± 5 s-1, respectively. Dramatically enhanced biocatalytic activity was exemplified at the Mb/HAGCE for the reduction of hydrogen peroxide (H2O2), trichloroacetic acid (TCA) and oxygen (O2). The Mb/ArHA film was also characterized by UV-vis spectra, scanning electron microscope (SEM) indicating excellent stability and good biocompatibility for protein in the film. The applicability of the method to the determination of H2O2 (∼3%) in a commercial antiseptic solution and soft-contact lenses cleaning solutions were demonstrated. This new Mb/HAGCE exhibited rapid electrochemical response (with in 2 s) with good stability in physiological condition. © 2007 Elsevier B.V. All rights reserved.