Fiber-optic bio-sniffer (biochemical gas sensor) for high-selective monitoring of ethanol vapor using 335 nm UV-LED

A fiber-optic bio-sniffer (biochemical gas sensor) for continuous monitoring of gaseous alcohol with high sensitivity and high-selectivity was fabricated and tested. The bio-sniffer uses alcohol dehydrogenase (ADH) for recognition of ethanol. Usually, enzyme loses activity in the gas phase. The bio-sniffer solved this problem by applying a flow-cell to refresh and wet the enzyme immobilized membrane by circulating phosphate buffer (PB). The bio-sniffer measures ethanol vapor by measuring fluorescence of nicotinamide adenine dinucleotide (NADH), which is produced by enzymatic reaction at the flow-cell. In order to construct a simplified system suitable for on-site applications, a high-intensity ultraviolet light emitting diode (UV-LED) was utilized as an excitation source. Assessment of the bio-sniffer was performed using a standard gas generator. First, the operating condition of the bio-sniffer was optimized by investigating fluorescent spectrum and the dependence of fluorescent characteristics on flow-rate of PB. As a result, the bio-sniffer was confirmed to be useful for continuous gas monitoring and the calibration range was 0.30–300 ppm. High-selectivity due to specific activity of enzyme was also confirmed. Thus, the ADH bio-sniffer was expected to be useful for breath analysis or medical screening applications.