Noninvasive Monitoring of Transporter−Substrate Interaction at Cell Membrane

We report noninvasive monitoring of the transporter-substrate interaction at the cell membrane using an oocyte-based field effect transistor (FET), which is based on detection of extracellular potential change induced as a result of the interaction between transporting peptide and substrate at the cell membrane. The interface potential change at the cell membrane/gate insulator interface can be monitored during the uptake of substrate mediated by transporter without any labeling materials and fracturing oocyte. Moreover, we can discriminate the transporting kinetics of the substrate mediated by the wild-type and the mutant-type transporters by use of the oocyte-based FETs. Our findings on the time course of the interface potential would provide important information to understand the molecular mechanism of the uptake kinetics for the OATP-C transporter.