Aims: to develop a fast biomimetic method to deposit nanocrystalline calcium phosphate coatings on titanium substrates.

Methods: Ti6Al4V disks (diameter = 15mm) were ultrasonically cleaned with acetone, ethanol and demineralized water, and then etched in a mixture of HF and HNO3. The disks were soaked in a supersaturated Ca/P solution at 37A1C, pH 7.2 for different periods of time up to 3 days. The structure and morphology of the obtained coatings were characterized using thin film X-ray diffraction, SEM and TEM investigation. Furthermore, coated and uncoated diskes were soaked in simulated body fluid (SBF) for different periods of time.

Results: the first calcium phosphate deposits on the etched Ti6Al4V disks can be appreciated after 7 days of soaking in SBF solution. At variance, soaking of the Ti6Al4V disks in the supersaturated Ca/P solution, with a simpler composition than that of SBF, yields the deposition of a uniform calcium phosphate coating in a few hours. Thin film X-ray diffraction patterns show that the coating is constituted of a poor crystalline apatitic phase, and that the extent of deposition increases on increasing the soaking time in the supersaturated solution. TEM images recorded on the material detached from the coating by ultrasound vibration show that the apatitic deposition is constituted of thin nanocrystals. The results obtained on coated substrates submitted to interaction with SBF indicate that the presence of the coating reduces the time required to appreciate the deposition of apatite from SBF to just 24 hours.

Conclusions: the method utilized in this work can be successfully applied to obtain fast deposition of uniform coatings of nanocrystalline hydroxyapatite on titanium substrates.