Bio-sniffer for intermittent repetitive measurement of acetone and isopropanol in exhaled breath

We developed a fiber-optic biochemical gas sensor (bio-sniffer) which can measure acetone and isopropanol (IPA) for lipid metabolism evaluation and diabetes screening. We applied to intermittent measurement of the both components in exhaled air. The bio-sniffer utilized a reduction reaction of acetone (pH7.5) and an oxidation reaction of IPA (pH8.5) by secondary alcohol dehydrogenase (S-ADH). The nicotinamide adenine dinucleotide (NADH) consumed (produced) in these reactions was excited by UV light (λ = 340 nm), and the autofluorescence from NADH (λ = 490 nm) was detected by a photomultiplier tube (PMT). Using this principle, we measured acetone and IPA gases intermittently by switching pH and the coenzyme (NADH / NAD+). The dynamic ranges of the sensor were 10-3000 ppb for acetone and 2-1000 ppb for IPA, which encompassed the breath concentration of healthy people (acetone: 200-900 ppb, IPA: 10-30 ppb). Finally, the bio-sniffer was applied to healthy person's breath and showed the similar responses to the standard gases. These results indicate the usefulness of the bio-sniffer in breath measurement.