Neuronal interfaces based on UV-activated TiO2 thin films grown via atomic layer deposition

Implantable medical devices for neuro-stimulation and/or recording are strategic in neuroscience research, for the therapy of neurological disorders and bioelectronics. Achieving long-term stability of the neuroelectronic interface is paramount for their specific applications. Dielectric encapsulation of neural devices is mandatory to prevent electrode degradation, increase interface biocompatibility, and enhance capacitive coupling. In this work, high-k dielectric nanostructured TiO2 thin films were conformally grown on silicon substrates via Atomic Layer Deposition (ALD) as encapsulating materials for neural devices. The electrical and electrochemical behavior of downscaled ALD-TiO2 films was investigated together with biocompatibility and electrophysiological properties of neuronal cells. Electrochemical analyses evidenced a non-faradaic range and a cathodic threshold voltage, indicating the suitability of TiO2 materials for implantable electrodes. Furthermore, a simple UV-assisted surface activation method was established to obtain highly wettable surfaces. This research demonstrates the efficacy of ALD technique, combined with a facile, rapid, and cost-effective UV surface treatment, to produce superhydrophilic encapsulating TiO2 thin films exhibiting excellent biocompatibility. Electrophysiological investigations of neurons in vitro cultured on UV-irradiated TiO2 films revealed robust action potentials and favorable passive membrane properties, highlighting enhanced neuronal compatibility and offering excellent prospects for applications in implantable neural interfaces.