Formation of carbonated hydroxyapatite films on metallic surfaces using dihexadecyl phosphate–LB film as template

• The presence of molecularly organized phospholipid matrices leads to nucleation of calcium phosphates in specific sites.
• The mineral phase is compositionally similar to the human bone.
• Surface chemistry is more important than surface roughness for improving cell proliferation.
• The LB–hydroxyapatite film is bioactive and responsible for the increase in osteoblastic cell viability.

Hydroxyapatite serves as a bioactive material for biomedical purposes, because it shares similarities with the inorganic part of the bone. However, how this material deposits on metallic surfaces using biomimetic matrices remains unclear. In this study, we deposited dihexadecyl phosphate, a phospholipid that bears a simple chemical structure, on stainless steel and titanium surfaces using the Langmuir–Blodgett (LB) technique; we employed the resulting matrix to grow carbonated hydroxyapatite. We obtained the calcium phosphate coating via a two-step process: we immersed the surfaces modified with the LB films into phosphate buffer, and then, we exposed the metal to a solution that simulated the concentration of ions in the human plasma. The latter step generated carbonated hydroxyapatite, the same mineral existing in the bone. The free energy related to the surface roughness and composition increased after we modified the supports. We investigated the film morphology by scanning electron and atomic force microscopies and determined surface composition by infrared spectroscopy and energy dispersive X-ray. We also studied the role of the surface roughness and the surface chemistry on cell viability. The surface-modified Ti significantly increased osteoblastic cells proliferation, supporting the potential use of these surfaces as osteogenic materials.

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