In this study, an ultra-sensitive hydrogen peroxide sensor was fabricated by using horseradish peroxidase (HRP)-immobilized conducting polymer, polyaniline (PANI). With the proposed detection mechanism, hydrogen peroxide first oxidizes HRP, which then oxidizes polyaniline, thus resulting in decreased conductivity of the polyaniline thin film. The reduced HRP can be further oxidized by hydrogen peroxide and the cycle of the oxidation/reduction interaction would proceed until all hydrogen peroxide are reacted. It leads to the high sensitivity of the sensor due to the signal contributed from all reacted hydrogen peroxide. The detection limit of the hydrogen peroxide sensor is 0.7 nM. The detecting range of concentration of H2O2 is from 0.7 nM to 1 μM. The simple fabrication for the sensor allows the sensor to be cost-effective and disposable. This ultra-sensitive hydrogen peroxide sensor is promising in applications for low concentration hydrogen peroxide detections, such as the reactive oxygen species (ROS) in oxidative stress studies.
