Direct Electrochemical Reaction of Phytohemagglutinin Adsorbed at the Multi-Walled Carbon Nanotubes Modified Glassy Carbon Electrode

Abstract

Electrochemical behavior of phytohemagglutinin (PHA) was investigated by its adsorption at the multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE). Protein was transferred at the electrode surface as MWCNTs-cetyl trimethylammonium bromide (CTAB) nanocomposite film. UV–Vis absorption spectroscopy was employed to reveal the relative binding affinity of PHA coupled to the MWCNTs-CTAB. The protein-MWCNTs-CTAB film was characterized using fluorescence imaging, scanning electron microscopy (SEM) and impedance spectroscopy. The direct electron transfer between PHA in MWCNTs-CTAB films and the electrode was studied with electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry and square wave voltammetry. Electrochemical parameters; such as number of electrons transferred (n), formal potential (E°′) and electron transfer rate constant (ks) for the electrode reaction were calculated. Cyclic voltammograms of the electrode in phosphate buffer solution of pH 7.0 showed well defined reversible peaks at −0.23 and −0.25 V vs. SCE, in the positive and negative going scans, respectively. These peaks are probably related to the oxidation and reduction of iron ions. Furthermore the presence of iron ions was established by atomic absorption spectroscopy. These results show that PHA can act as an iron storage protein.