Cytocompatibility Assessment of Si, Plasma Enhanced Chemical Vapor Deposition-Formed SiO₂ and Si₃N₄ Used for Neural Prosthesis: A Comparative Study

SiO₂ and Si₃N₄ layers to be used in the microfabrication of a neural probe were formed on Si substrate through plasma enhanced chemical vapor deposition (PECVD). To ensure their cytocompatibility, the surface properties and cytocompatibility of the PECVD-formed SiO₂ and Si₃N₄ were investigated and compared. SEM images showed the SiO₂ and Si₃N₄ layers consisted of nano-sized particles. In accordance with water contact angle measurement, the surface of both PECVD-formed SiO₂ and Si₃N₄ layers were hydrophilic and there was no significant difference in wettability between them. A breast cancer cell line (MCF-7) was seeded on their surface to evaluate the cytocompatibility. After 3 days of cell culture, the adherent cells on PECVD-formed Si₃N₄ surface did not spread as well as those on Si or PECVD-formed SiO₂, and the cells on the surface of PECVD-formed SiO₂ and Si₃N₄ were significantly less than on Si. At day 7, however, there was no significant difference between them, in terms of cell morphology and number. Therefore, the PECVD-formed SiO₂ and Si₃N₄ layers did not exhibit acute cytotoxicity and were as cytocompatible as tissue culture polystyrene.