Intercalation of methylene blue into layered manganese oxide and application of the resulting material in a reagentless hydrogen peroxide biosensor

Methylene blue (MB) has been intercalated into layered manganese oxide (birnessite) by a delamination/reassembly process and the resulting MB-intercalated birnessite (MB-Bir) material characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and electrochemical measurements. A novel reagentless hydrogen peroxide biosensor was fabricated by using the MB-Bir as an electron mediator. Cyclic voltammetry and amperometric measurements demonstrated that methylene blue coimmobilized with horseradish peroxidase (HRP) displayed good stability and that electrons were efficiently shuttled between HRP and the electrode. The biosensor showed a rapid and linear response to H2O2 over the range from 1.5 × 10−6 M to 8.1 × 10−3 M, with a detection limit of 1.3 μM (S/N = 3/1). Moreover, the biosensor retained about 85% of its original response to H2O2 after storage for 2 months. Addition of glucose, sucrose, citric acid, acetic acid, or l-ascorbate did not interfere with the H2O2 response.