Bioelectrical Nose Using Odorant-Binding Protein as a Molecular Transporter Mimicking Human Olfactory System for Direct Gas Sensing

We report a portable bioelectronic nose using odorant-binding protein (OBP) as a molecular transporter for the direct detection of odorant gas molecules. In this study, a 3D-printed case with a gas-permeable membrane on one side was filled with an OBP solution, and an olfactory receptor-functionalized carbon nanotube FET (CNT-FET) was inserted to the case. Here, OBP molecules in the solution were utilized as a vehicle to transport odorant gases to olfactory receptor on a CNT-FET device, mimicking human olfactory system. Our bioelectronic nose platform based on I7 receptor dose-dependently responded to octanal gas in real time and the sensitivity improved by ~100% compared with those without OBP. Furthermore, it also be used to detect odorant gas molecules from orange juice scent, and the bioelectronic nose with OBP showed a higher sensitivity than those without it. Since our bioelectronic nose platform allows us to directly detect gas-phase odorant molecules including a rather insoluble species, it could be a powerful tool for versatile applications and basic research based on a bioelectronic nose.