Functionalization of Titanium Surfaces Using Laser Ablation in Vacuum and Liquid by Hydrolytically Instable Casi2 Affects Behavior of Bone Healing-Related Cell Types

Calcium silicide (CaSi2) instability in humid air or pH-neutral water remains unknown, although the topochemical formation of silicene from CaSi2 in various aqueous phases is a well-known process. Here we report on laser ablation of CaSi2 in the vacuum and ethanol, characterize coats deposited on titanium substrates with electron microscopy, X-ray photoelectron, Raman and infrared spectroscopy, and examine the instability of the deposited coats in humid air and neutral water.We further investigate the behavior of human mesenchymal stromal cells (hMSCs), vascular cells (HUVECS, human umbilical vein endothelial cells) and macrophages (derived from THP-1 cell line) in contact with deposited coatings submerged in cell culture medium. The observed results indicate that CaSi2 undergoes topochemical conversion to silicene accompanied by hydrolytic reactions leading to inorganic Ca compounds and SiO2, and that the response of all cell types in the hydrolyzed CaSi2 surface is negatively affected by the nature of the hydrolytic products. In contrast, cells showed a tendency for enhanced biocompatibility towards the CaSi2 particles ablated in vacuum.  Altogether, the results suggest that coating approaches can significantly influence cell behavior outcomes.