Field-effect transistor with recombinant potassium channels: fast and slow response by electrical and chemical interactions

Electrical interfacing of semiconductor devices with ion channels is the basis for a development of neuroelectronic systems and of cell-based biospecific electronic sensors. To elucidate the mechanism of cell–chip coupling, we studied the voltage-gated potassium channel Kv1.3 in HEK 293 cells on field-effect transistors in silicon with a metal-free gate of silicon dioxide. Upon intracellular depolarization there is a positive change of the effective extracellular voltage on the transistor with an amplitude that correlates with the gating of Kv1.3 channels, but with a dynamics that is far slower than channel gating. After repolarization there is a fast negative change of the transistor signal followed by a slow relaxation dynamics without any membrane current. To rationalize the involved transistor response, we propose a concept that combines the electrodiffusion of ions in the cell–chip junction with selective ion binding in the electrical double layer of silicon dioxide. The model implies (i) an electrical charging and discharging of the cell–chip capacitance within a microsecond, (ii) a changing K+ concentration in the cell–chip junction within a millisecond and (iii) a changing adsorption of K+ and Na+ ions within tens of milliseconds. The total transistor signal is a superposition of the changed electrical potential in the extracellular space between cell and chip and of the changed surface potential at the chip surface. PACS 73.40.Mr; 82.45.Vp; 85.30.Tv; 87.16.Uv; 87.19.Nn