Development of Ultrasensitive Sweet Taste Sensor Based on Venus Flytrap Domain of Human Sweet Taste Receptor

Evaluation of sweet taste is essential for the survival of humans. Sweetness is the taste of carbohydrates such as monosaccharides and polysaccharides. The human taste system favors sweet carbohydrates, helping to ingest energy sources, but excessive sugar intake can cause various metabolic syndromes and can be life-threatening. Therefore, it is important to sensitively evaluate sweetness in various environments. There are various devices that can detect sweet taste substances, but there is no device that can simulate the human gustatory system in various environments. We developed an ultrasensitive bioelectronictongue that can mimic human sweetness based on the ligand binding domain of the human sweet receptor. We overexpressed only the ligand-binding domain (venus flytrap) of the human sweet taste receptor instead of the whole receptor. Then, the domain was immobilizedon the carbon nanotube field-effect transistor with floating electrodes. Our bioelectronic tongue can selectively detect sweet substances ata concentration of 0.1 fM, which is a 10^7-fold improvement in sensitivity compared to previous methods. This high sensitivity is due to the small size of the T1R2 VFT domain, which can be placed within the Debye length of the sensor surface. Furthermore, our sensors could show how our sweet taste receptors respond to sweet taste substances in a variety of environments. The sensor could evaluate sweeteners in real beverages such as apple juice and chamomile tea. In addition, we can evaluate the inhibition and enhancement of taste sensation by various chemical species such as zinc ions and amino acids. Importantly, our device showed significantly improved storability and reusability which could be important for future practical applications.