Immobilization of horseradish peroxidase onto a gold-nanoparticle-adsorbed poly(thionine) film for the construction of a hydrogen peroxide biosensor

An amperometric hydrogen peroxide (H ₂O ₂) biosensor was developed based on the immobilization of horseradish peroxidase (HRP) onto a gold-nanoparticle (GNP)-adsorbed conducting poly(thionine) (PTH) film. The modification procey ss I was cha aracterized by scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The effects of experimental parameters such as the concentration of the mediator (hydroquinone, HQ), the pH of the solution, and the working potential were investigated for optimum analytical performance. In the presence of the mediator, the immobilized HRP showed excellent electrocatalytic activity towards the reduction of H ₂O ₂. The linear dynamic range of 5-150 μLM with the regression coefficient of 0.999 was obtained. The detection limit was calculated to be 1.5 μLM based on a signal-to-noise ratio of 3. The reproducibility, repeatability, and stability of the biosensor were studied, with satisfactory results. The biosensor performance was evaluated with respect to the possible interferences and the application of the biosensor to real-sample analysis.