Sodium channels are the crucial electrical elements of neuronal excitation. As a step towards hybrid neuron-semiconductor devices, we studied the activation of recombinant NaV1.4 sodium channels in human embryonic kidney (HEK293) cells by stimulation from an electrolyte/oxide/silicon (EOS) capacitor. HfO2 was used as insulator to attain a high capacitance. An effective activation was achieved by decaying voltage ramps at constant intracellular voltage at a depleted NaCl concentration in the bath to enhance the resistance of the cell-chip contact. We were also able to open sodium channels at a NaCl concentration close to physiological conditions. This experiment provides a basis for noninvasive capacitive stimulation of nerve cells with semiconductor chips.
Extracellular capacitive activation of NaV1.4 channels in HEK293 cells at a reversed concentration gradient of Na+ ions. (a) Decaying voltage ramp VS applied to the capacitor. (b) Pipette current IP at an intracellular voltage VM=-100 mV (black line) and at VM=-20 mV with inactivated channels (red line). The amplitude of the truncated current peaks at both ends of the voltage ramp was +-4.5nA. (c) Numerical simulation of membrane current IJM through the attached cell membrane for VM=-100 mV (full line) and VM=-20 mV (red line).
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