Detection of bitterness in vitro by a novel male mouse germ cell-based biosensor

Bitter detection has attracted extensive attention in industries and researches due to pharmacological and/or food safety issues. Common electronic tongues constructed with electrochemical, optical or mass sensors are often subjected to the drawback of low-specificity in detecting a wide range of bitter compounds with diverse chemical structures and functions. However, biological gustatory components present unique specificity to bitter compounds, which may provide a promising approach in bitter detection. The activation of G protein coupled receptors (GPCRs) by ligands will affect cell morphology in a specific manner, which can be monitored by cell-impedance sensor. Thus cells expressing bitter receptors (a subfamily of GPCRs) can be used as sensing material in specific bitter detection. In this study, we explored the feasibility of utilizing male mouse germ cells in testis and cell-based impedance sensors (CIS) to build a cell-based bitter biosensor. Male mouse germ cells express bitter receptor T2Rs, which can sensitively and specifically respond to bitter compounds. To verify bitter sensing capacity of the germ cells, calcium responses of germ cells to three bitter compounds were examined prior to cell impedance response measurement. Furthermore, a bitter receptor blocker, probenecid, was used to verify the specificity of T2R-mediated impedance responses in germ cells. Cell-impedance response profiles of germ cells to four bitter compounds were investigated by analyzing the response intensity under various concentrations. Finally, impedance responses to five basic tastes were examined to evaluate the performance of cell-based bitter biosensor in bitter detection. The results revealed that this hybrid bitter biosensor could respond to those bitter compounds in a dose-dependent manner. The detection threshold for quinine was 0.125mM, lower than our previous cell-based bitter biosensor. The calcium imaging tests and use of probenecid confirmed that T2R activation contributed to the cell impedance responses of this cell-based biosensor. Moreover, this germ cell-based cell could specifically detect bitter compounds among five taste stimuli, which may provide a promising and valuable approach for detection of various bitter compounds.