A hydrogen peroxide biosensor based on Langmuir-Blodgett technique: Direct electron transfer of hemoglobin in octadecylamine layer

The present paper describes the modification of hemoglobin (Hb)-octadecylamine (ODA) Langmuir-Blodgett (LB) film on a gold electrode surface to develop a novel electrochemical biosensor for the detection of hydrogen peroxide. Atomic force microscopy (AFM) image of Hb-ODA LB film indicated Hb molecules existed in ODA layer in a well-ordered and compact form. The immobilized Hb displayed a couple of stable and well-defined redox peaks with an electron transfer rate constant of 4.58 ± 0.95 s⁻¹ and a formal potential of −185 mV (versus Ag/AgCl) in phosphate buffer (1.0 mM, pH 5.0) contain 0.1 M KCl at a scan rate of 200 mV s⁻¹, characteristic of Hb heme Fe(III)/Fe(II) redox couple. The formal potential of Hb heme Fe(III)/Fe(II) redox couple in ODA film shifted linearly between pH 5 and 8 with a slope of −23.8 mV pH⁻¹, suggesting that proton took part in electrochemical reaction. The ODA could accelerate the electron transfer between Hb and the electrode. This modified electrode showed an electrochemical activity to the reduction of hydrogen peroxide (H₂O₂) without the aid of any electron mediator.