A neural cell culture study on thin film electrode materials.

Functional neural stimulation requires good interface between the neural cells and the electrode surfaces. In order to study the effect of electrode materials and surface structure on cell adhesion and biocompatibility, we cultured cortical neurons on thin films of platinum and iridium oxide. We used both flat, as-deposited and laser micro-structured films. The laser micro-structuring consisted of creating regular arrays of micro-bumps or holes with diameters of 4-5 mum and height of about 1.5 mum. The micro-bumps were fabricated onto platinum and iridium film surfaces deposited on borosilicate glass substrates, using mask-projection irradiation with single nano-second pulses from a KrF excimer laser (lambda = 248 nm). Amorphous and crystalline (deposited at 250 degrees C) IrO(2) films were deposited onto the laser micro-structured iridium films by pulsed-DC reactive sputtering to obtain micro-structured IrO(2) films. Cortical neurons isolated from rat embryo brain were cultured onto these film surfaces. Our results indicate that flat and micro-structured film surfaces are biocompatible and non-toxic for neural cell growth. The use of poly-D: -lysine as a mediator for cell adhesion onto the thin film surfaces is also discussed.