Effects of a Hydroxyapatite-Coated Nanotube Surface of Titanium on MC3T3-E1 Cells: An In Vitro Study

Purpose: To compare the biological behavior of mouse osteoblast-like cells (MC3T3-E1) on hydroxyapatite (HA)-coated nanotube surface of titanium and plasma-sprayed HA (HA-PS)-coated titanium surface. Materials and Methods: The HA-coated nanotube surface of titanium were fabricated by anodization coupled with alternative immersion method (AIM). MC3T3-E1 osteoblast cells cultured in vitro were seeded onto these different surfaces; their growth states were examined by a confocal laser scanning microscope; the proliferation behavior, alkaline phosphatase (ALP) activity, osteocalcin (OCN) secretion, and analysis of osteoblastic gene expressions were also compared in detail. Results: Significant increases in ALP activity and OCN production on days 7 and 14 (P < 0.05) were observed for AIM-coated HA (HA-AIM) surfaces. However, cells cultured on HA-AIM-coated surfaces showed a delayed growth pattern. Real-time polymerase chain reaction analyses showed significantly higher relative mRNA expression levels of osteoblastic genes (runt-related protein 2, osterix, osteopontin, OCN) in cells cultured on the HA-AIM-coated nanotube surfaces as compared with cells cultured on the HA-PS and baer Ti surfaces. Conclusion: The current research showed that the HA-AIM-coated nanotubular Ti surfaces enhance osteoblast differentiation, which had the potential to further improve osseointegration.