Hydrogel-based Bioelectronic Tongue for the Evaluation of Umami Taste in Fermented Fish

Bioelectronic tongues based on umami taste receptors have recently been reported for versatile applications such as food analyses. However, their practical applications are still limited, partly due to their limited stability and non-specific responses in real sample environments. Herein, we have developed a hydrogel-based bioelectronic tongue for the sensitive assessment of umami intensity in fish extract samples. In this study, the T1R1 venus flytrap of an umami taste receptor was immobilized on the gold floating electrodes of a carbon nanotube-based field-effect transistor. A polyacrylamide conducting hydrogel film was further hybridized on the sensor surface via physical adsorption, which could provide a good physiological environment to maintain the activity of receptors due to its excellent hydrophilicity and biocompatibility. The bioelectronic tongue with a receptor-embedded hydrogel structure showed a sensitive detection of umami substances down to 1 fM, and it also had a wide detection range of 10^-15-10^-2 M for monosodium glutamate and disodium inosinate, which covers the human taste threshold. More importantly, the proposed sensor could significantly reduce the non-specific binding of non-target molecules to a carbon nanotube channel as well as exhibit long-term stability, enabling sensitive detection of umami substances even in fish extract samples. Our hydrogel-based bioelectronic tongue provides a promising platform for future applications such as the flavor evaluation of foods and beverages.