A novel hydrogen peroxide biosensor based on the immobilization of horseradish peroxidase onto Au-modified titanium dioxide nanotube arrays

In this study, we report on a promising H2O2 biosensor based on the co-immobilization of horseradish peroxidase (HRP) and chitosan onto Au-modified TiO2 nanotube arrays. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; a gold thin film was then uniformly coated onto the TiO2 nanotube arrays by an argon plasma technique. The morphology and composition of the fabricated Au-modified TiO2 nanotube arrays were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry and chronoamperometry were used to study and to optimize the performance of the resulting electrochemical biosensor. The effect of pH, applied electrode potential, the presence of the electron-mediator methylene blue, and the anodic oxidation time of the Ti substrate on the electrochemical biosensor has been systemically studied. Our electrochemical measurements show that the Au-modified TiO2 nanotube arrays provide excellent matrices for the immobilization of HRP and that the optimized electrochemical biosensor exhibits long linearity, a low detection limit, high stability and very good reproducibility for the detection of H2O2. Under the optimized conditions the linearity of the developed biosensor for the detection of H2O2 is observed from 5 × 10−6 to 4 × 10−4 mol l−1 with a detection limit of 2 × 10−6 mol l−1 (based on the S/N = 3).