TiO₂ surfaces support neuron growth during electric field stimulation

TiO₂ is proposed here for the first time as a substrate for neural prostheses that involve electrical stimulation. Several characteristics make TiO₂ an attractive material: Its electrochemical behaviour as an insulator prevents surface changes during stimulation. Hydration creates -OH groups at the surface, which aid cell adhesion by interaction with inorganic ions and macromolecules in cell membranes. Its ability to neutralize reactive oxygen and nitrogen species that trigger inflammatory processes confers biocompatibility properties in dark conditions. Here, physicochemical characterization of TiO₂ samples and their surfaces was carried out by X-ray diffraction, X-ray photoelectronic emission spectroscopy, scanning electron microscopy, atomic force microscopy and by contact angle measurements. Its properties were related to the growth parameters and morphology of amphibian spinal neurons cultured on TiO₂ samples. Neurons adhered to and extended neurites directly on TiO₂ surfaces without pre-coating with adhesive molecules, indicating that the material permits intimate neuron-surface interactions. On TiO₂ surfaces the distal tips of each extending neurite and the neurite shafts themselves showed more complex filopodial morphology compared with control cultures on glass. Importantly, the ability of TiO₂ to support neuron growth during electric field exposure was also tested. The extent of growth and the degree of neurite orientation relative to the electric field on TiO₂ approximated that on glass control substrates. Collectively, the data suggest that TiO₂ materials support neuron growth and that they have potential utility for neural prosthetic applications incorporating electric field stimulation, especially where intimate contact of neurons with the material is beneficial.