Immobilization of horseradish peroxidase and nile blue into the ormosil nanocomposite for the fabrication of hydrogen peroxide biosensor based on MWCNT modified glassy carbon electrode

A novel approach to construct a second-generation amperometric biosensor is described. The classical redox dye nile blue (NB) as mediator and horseradish peroxidase as a base enzyme were coimmobilized into the multiwalled carbon nanotubes (MWCNTs) modified ormosil matrix. Nafion was dispersed into the matrix to enhance the rate of the electron transfer and prevent the cracking of the ormosil film. The surface morphology of MWCNT/NB/NAF/HRP nanocomposite was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry and amperometry measurements were used to study and optimize the performance of the resulting peroxide biosensor. The apparent Michaelis-Menten constant was determined to be 1.1 mM. The effect of pH, applied potential and amount of the HRP enzyme on the electrochemical biosensor has been systematically studied. The fabricated biosensor demonstrated significant electrocatalytic activity for the reduction of hydrogen peroxide with wide linear range from 2 x 10(-7) to 3.8 x 10(-4) M, and low detection limit 1 x 10(-7) M (S/N = 3) with fast response time <3 s. The facile procedure of immobilizing HRP and MWCNTs into the ormosil used in the present work can promote the development of electrochemical research for enzymes, proteins, biosensors, biofuel cells and other bioelectrochemical devices. (C) 2009 Elsevier B.V. All rights reserved.