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.

Aims: to investigate the role of gelatin on the setting properties of α-tricalcium phosphate based cement.

Methods: gelatin α-TCP powders were prepared by grinding and sieving the solid compounds obtained by casting gelatin aqueous solutions containing a-TCP. 5% wt of CaHPO42H2O were added to the cement powders before mixing with the liquid phase, with a L/P ratio of 0.3 mL/g. Teflon moulds were used to prepare cement cylinders 6 mm in diameter and 12 mm high. X-ray diffraction analysis, mechanical tests, SEM, dsc and TG investigations were carried out on the cements after different times of soaking in SBF.

Results: The setting reaction of the control cement is completed in 7 days, whereas the transformation into apatite of the cements at high gelatin content occurs in just 2 days of aging in SBF. The fractured surface of the aged control cement is covered with entangled plate like apatite crystals, whereas gelatin cements display much more compact surfaces, most likely because of the inhibiting effect of gelatin on apatite crystal growth. The microstructural modifications are in agreement with the reduction of the total porosity, and with the improvement of the mechanical properties of the aged cements, on increasing gelatin content. The compressive strength of the cements increases linearly with the increase of gelatin. The results of the thermogravimetric analysis indicate a strong interaction between gelatin and hydroxyapatite crystals.

Conclusions: the results of this paper indicate that gelatin can be successfully used to improve and modulate the mechanical properties of α-TCP-based cements.