Physico-chemical properties of the Ti5O9 Magneli phase with potential application as a neural stimulation electrode

Abstract

This work offers a description of the physico-chemical and electrochemical properties of one of the titanium-based Magneli phases, known as Ti_nO_2n−1, for its possible application as an electrode for neural tissue stimulation in neural disorders and Central Nervous System (CNS) injuries. Ti₅O₉ is one of the less-known Magneli phases that exhibits high electronic conductivity and high chemical and thermal inertness. The material, prepared in a reducing atmosphere by ceramic methods, is composed of a porous surface responsible for most of its properties. Chemical and physical features of the surface were studied with the aim of establishing a relationship between them and the surface electrochemistry. The chemical composition of the surface was studied by XRD and XPS. The topography was studied by AFM and the morphology of the outer side of a fracture was observed by SEM. The conductivity was measured by the four point method in DC finding extremely high values, 9500 S cm⁻¹ at 37 °C. The study of the surface electrochemistry in contact with media, which simulate physiological conditions, was carried out by cyclic voltammetry and EIS. With these measurements the charge injection mechanism has been elucidated, and the charge storage capacity of the material has been determined, finding higher values than those reported for other ceramic electrodes. Finally, cell cultures realised with neural cells were obtained from the cerebral cortex of E18 Wistar rat embryos. They were observed after 4 and 10 DIV and helped in the determination of the biocompatibility of the material.