Amperometric alcohol sensors based on protein multilayers composed of avidin and biotin-labeled alcohol oxidase

Protein multilayers composed of avidin and biotin-labeled alcohol oxidase (AOx) were prepared on the surface of a platinum (Pt) electrode by repeated deposition of the proteins to develop amperometric alcohol sensors. The AOx multilayer-modified sensors showed a rapid response to ethanol over the concentration range of 0.01-10 mg/100 mL. The output current of the sensor depended linearly upon the thickness of the AOx layers (or the number of the AOx layers), suggesting that a constant amount of AOx can be immobilized by each deposition. The selectivity of the sensor to aliphatic alcohols was in the order of methanol > ethanol > n-propanol > n-butanol, being in accord with the selectivity of AOx in a homogeneous system itself. The sensor retained its original response to ethanol for about one month without deterioration.