Towards Growth Cone Guidance On Silicon Chips By Capacitive Stimulation Of Voltage Dependent Ca2+ Channels

Abstract

Hybrid systems of neuronal networks and microelectronic chips can be used to elucidate network processes like learning and memory. Systematic experiments on network dynamics require a well defined topology of the synaptic connections.We want to control the directional outgrowth of neurites directly from the chip. Intracellular Ca2+ concentration [Ca2+]i of growth cones is known to play a decisive role in neuronal outgrowth. By capacitive stimulation of voltage dependent Ca2+ channels (VDCCs) we want to manipulate [Ca2+]i to steer growth cone guidance.To show the feasibility of capacitive opening of VDCCs, we used HEK293 cells expressing L-type VDCC Cav1.2. The capacitive gating of Cav1.2 was studied under whole cell voltage clamp and current clamp conditions. We detected the Ca2+ influx by Fura-2 fluorescence microscopy. We found that the cells [Ca2+]i was greatly enhanced by repetitive capacitive chip stimulation.In a next set of experiments, we stimulated VDCCs in large, nonmotile growth cones of A-Cluster neurons from fresh water snail Lymnea stagnalis. We monitored growth cone [Ca2+]i by Fura-2 fluorescence microscopy and found that repetitive capacitive stimulation induced profound changes in [Ca2+]i. Observation of growth cone morphology before, during and after repetitive stimulation revealed significant structural reorganisation that relates to growth cone collapse and repulsion.Our results provide a first step towards capacitive control of growth cone guidance on silicon chips. Further experiments with smaller, motile growth cones have to be performed to achieve chip-controlled directional neurite outgrowth.