In vitro biocompatibility of Ti-Cp vs Ti-26Nb alloys on Saos-2 and THP-1 cells

This study assess the biocompatibility of Ti-26Nb compared to Ti-Cp, a reference in implantology, through the combination of conventional toxicological assay, morphological observations and transcriptomic analysis performed on two different cells line : Saos-2 and THP-1. The biocompatibility of Ti-Cp implants was evaluated in comparison with Ti-26Nb implants both having a mirror polished surface, studying cell proliferation (trypan blue and WST-1) and cell morphology/adhesion (SEM) on human THP-1 and Saos-2 cell lines. Finally, an evaluation of a potential toxicity of potassium niobiate powder KNbO3 was carried out by measuring metabolic activity and realizing a transcriptomic study on the THP-1 line (the first one) to deepen the results observed with Ti-26Nb discs. Indeed, niobiate ions are potentially released from implant in cellular acidic environnement. Concerning Saos-2 cells, our results suggest that Ti-26Nb and Ti-Cp discs do not impact proliferation and viability. Concerning THP-1 cell line, a decrease in proliferation and viability is observed in contact of Ti-26Nb discs (hypothesis of a cell-line effect ?, no biocompatibility study on monocyte/macrophage cell lines such as THP-1 actually available in literature). KNbO3 powder does not impact viability of THP-1 cells and does not induce changes at molecular level. Taken together, these data suggest a possible toxicity of Ti-26Nb toward THP-1 cells not directly related to the niobium but perhaps to the manufacturing process of Titane niobium alloy. Changes in gene expression in THP-1 cells (1,5 million) incubated without (control) or with 25 ug/mL of KNbO3 powder for 24 h, were measured. Four biological replicates were performed as controls : T1 ; T2 ; T3 ; T4. Four biological replicates were performed in THP-1 cells exposed to 25 ug/mL of KNbO3 powder : E1 ; E2 ; E3 ; E4. A total of 8 samples (microarrays) was used.