Abstract
Hydroxyapatite (HAp) is a well-known synthetic biomaterial that has been extensively employed in orthopedic fields as bone grafts or coating of metallic implants. During recent years, ion doping or ionic substitution has been used to improve the performance of bioceramics. Owing to the benefits of a bioactive element such as boron (B) in bone health, and reported impaired bone growth or abnormal development of bone in case of boron deficiency, it was expected that doping of boron could make a positive effect on physicochemical and biological properties of HAp.
In this study, boron-doped hydroxyapatite (BHAp) was synthesized successfully through utilizing microwaved assisted wet precipitation route. X-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectrometry were used to characterize the phase purity, lattice parameters, degree of crystallinity, particle size and elemental composition of synthesized BHAp powders. Substitution of borate (BO33-) ion with the phosphate (PO43-) in HAp crystal caused lattice distortion due to radius difference between the dopant and the replaced element, which also led to smaller crystalline size and lower crystallinity degree in doped samples (∼ 91 % in 0.5 mol doped BHAp compared to 95 % of pure HAp). In vitro results revealed that although there was no significant difference in biodegradability of doped BHAp, after submerging samples in simulated body fluid for 14 days, intense growth of apatite particles (Ca/P ratio of 1.74) was observed on the surface of BHAp pellets, especially in samples with 0.25 and 0.5 mole B. Observed higher bioactivity was expected due to lower crystallinity degree of BHAp samples.
Due to the results of this study, incorporation of B into the structure of HAp could be considered as a positive step to improve the bioactivity and biological performance of these biomaterials in orthopedic applications.
