Biomimetic Hydroxyapatite Nanophases For Biomedical Applications

Several chemistry-based processing routes have been reported for preparing hydroxyapatite nanoparticles (nHA) powders. The aim of the this study was to demonstrate similarities and differences in physico-chemical properties of nHA powders synthesised by wet chemical precipitation following 4 different protocols.

Method:

Nano-sized HA powders were prepared following four different protocols as reported below:

Table 1. Wet-precipitation protocols and process parameters.

As-precipitated products were vacuum filtered, dried in oven at 60°C for few hours and calcinated at 650°C for 6h at the ramp rate of 5.0°C/min in a tube furnace. X-ray diffraction was performed on powdered samples. Microstructural features of as-precipitated powders were studied by TEM. FTIR-ATR spectra were recorded between 500 and 4000cm^–1.

Result:

XRD patterns showed in all samples only HA reflections. The crystallinity degree ranged between 40% for HA_Bb to about 70% for HA_Pr. TEM observations revealed that the precipitated powders are made of needle-like particles (width 10–20nm and 50–200nm length) for HA-Pr, HA_Ba and HA_Pg samples and globular granules (size 60-90nm) for Ha_Bb sample. FTIR-ATR spectra of the four powders show the characteristic bands of hydroxyapatite (vibrational modes of phosphate ions from 500 to 600cm–1 and 1000 to 1100cm–1 and stretching vibration of hydroxyl ions at 3570cm–1).

Conclusion:

Nanophase HA powders were successfully obtained, showing a different morphology (globular and needle-like morphologies) and cristallinity degree (from 40 up to 70%) depending on the different process parameters of the synthesis method used, such as temperature, ripening time and pH.