Gas-phase biosensors (Bio-sniffers, Sniff-cam) have been investigated not only for human volatiles (acetone, methyl mercaptan, trimethylamine, ethanol, isopropanol, etc.) but also for residential harmful VOCs (formaldehyde, toluene, nicotine) causing sick-house syndrome, etc. The biofluorometric bio-sniffers constructed with UV-LED and PMT shows good sensitivity and selectivity for continuous monitoring of target VOCs (formaldehyde, ethanol, acetaldehyde, acetone, isopropanol, etc.). The sniff-cam with enzyme immobilized mesh demonstrates a spatiotemporal gas-imaging for human volatiles (i.e. ethanol, acetaldehyde, etc. after drinking). As novel non-invasive biosensing approaches, the gas-phase biosensors for human and environmental VOCs will be introduced in this contribution. The bio-sniffer for acetone vapor was developed using S-ADH (secondary alcohol dehydrogenase) reverse reaction by detecting NADH fluorometric system. The S-ADH was possible to continuous measure gaseous acetone from less than 1 ppb to 20ppm with a good selectivity based on the enzyme specificity. The device allows to use the evaluation of the acetone concentration in exhaled air from healthy subjects and diabetes patients (type I and II). The novel biofluorometric sniff-cam for ethanol was also fabricated with ADH (alcohol dehydrogenase) immobilized mesh and the NADH visualization unit (UV-LED sheet array and high sensitive CCD), thus imaging human ethanol vapor not only exhaled air but also skin gas after drinking. The sniffer-device would be useful for conventional detecting the volatile biomarkers.
A fluorometric acetone biosniffer (biochemical gas sensor) for assessment of lipid metabolism utilizing reverse reaction of secondary alcohol dehydrogenase was constructed and evaluated. The biosniffer showed highly sensitivity and selectivity for continuous monitoring of gaseous acetone. The measurement of breath acetone concentration during fasting and aerobic exercise were also investigated. The acetone biosniffer provides a novel analytical tool for noninvasive evaluation of human lipid metabolism and it is also expected to use for the clinical and physiological applications such as monitoring the progression of diabetes.