Hydrogen peroxide biosensor based on a myoglobin/hydrophilic room temperature ionic liquid film

The composite film based on Nafion and hydrophilic room temperature ionic liquid (RTIL) 1-butyl-3-methyl-imidazolium chloride ([bmim]Cl) was used as an immobilization matrix to entrap myoglobin (Mb). The study of ionic liquid (IL)–Mb interaction by ultraviolet–visible (UV–vis) spectroscopy showed that Mb retains its native conformation in the presence of IL. The immobilized Mb displayed a pair of well-defined cyclic voltammetric peaks with a formal potential (Eo’) of −0.35 V in a 0.1 M phosphate buffer solution (PBS) of pH 7.0. The immobilized Mb exhibited excellent electrocatalytic response to the reduction of hydrogen peroxide, based on which a mediator-free amperometric biosensor for hydrogen peroxide was designed. The linear range for the determination of hydrogen peroxide was from 1.0 to 180 μM with a detection limit of 0.14 μM at a signal/noise ratio of 3. The apparent Michaelis constant (Kmapp) for the electrocatalytic reaction was 22.6 μM. The stability, repeatability, and selectivity of the sensor were evaluated. The proposed biosensor has a lower detection limit than many other IL–heme protein-based biosensors and is free from common interference in hydrogen peroxide biosensors.