Effects of semiconductor substrate and glia-free culture on the development of voltage-dependent currents in rat striatal neurones

An essential requirement for successful longterm coupling between neuronal assemblies and semiconductor devices is that the neurones must be able to fully develop their electrogenic repertoire when growing on semiconductor (silicon) substrates. While it has for some time been known that neurones may be cultured on silicon wafers insulated with SiO2 and Si3N4, an electrophysiological characterisation of their development under such conditions is lacking. The development of voltage-dependent membrane currents, especially of the rapid sodium inward current underlying the action potential, is of particular importance because the conductance change during the action potential determines the quality of cell-semiconductor coupling. We have cultured rat striatal neurones on either glass coverslips or silicon wafers insulated with SiO2 and Si3N4 using both serum-containing and serum-free media. We here report evidence that not only serum-free culture media but also growth on semiconductor surfaces may negatively affect the development of voltage-dependent currents in neurones. Furthermore, using surface-charge measurements with the atomic force microscope, we demonstrate a reduced negativity of the semiconductor surface compared to glass. The reduced surface charge may affect cellular development through an effect on the binding and/or orientation of extracellular matrix proteins, such as laminin. Our findings therefore suggest that semiconductor substrates are not entirely equivalent to glass in terms of their effects on neuronal cell growth and differentiation.