Dresden 2006 – scientific programme
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AKB: Biologische Physik
AKB 10: Neuroscience
AKB 10.7: Talk
Tuesday, March 28, 2006, 13:15–13:30, ZEU 255
Capacitive Stimulation of Neurons on Silicon Chips: Discrimination of Channel Opening and Electroporation — •Frank Wallrapp and Peter Fromherz — Department of Membrane and Neurophysics, Max Planck Institute for Biochemistry, Martinsried, Germany
The implementation of neuroelectronic systems requires a stimulation of neurons from silicon chips by capacitive interaction. The displacement current through a dielectric layer may give rise to extracellular and intracellular voltages that enhance the membrane conductance. Two mechanisms are feasible: (i) Opening of ion channels. (ii) Transient electroporation. Here, we show that both processes can be induced capacitively and discriminated with proper protocols of the applied voltage. In the model experiments, we use HEK293 cells, stably transfected with the K+ channel Kv1.3. We cultured them on TiO2-insulated silicon chips. By applying voltage ramps to the chip, we induce an extracellular voltage in the narrow cleft between cell and chip. For a given amplitude of negative voltage ramps, membrane current is solely due to K+ channels if the slope is beneath a certain threshold. The selectivity is checked with a toxin for Kv1.3. Above the threshold, a current component appears that is not blocked by the toxin. It is also observed for positive voltage ramps above a threshold of the slope. We assign it to electroporation. With respect to neuronal stimulation we conclude that rectangular voltage pulses applied to a capacitor inevitably elicit reversible electroporation. Selective activation of ion channels is achieved with slower voltage ramps of long duration that require a large amplitude and large capacitance.