Evaluation of bioactivity and biodegradability of Whitlockite nanoparticles (Ca18Mg2 (HPO4) 2 (PO4) 12) for bone regeneration

Treatment and repair of bone defects, has been a major challenge for bone regeneration activists for a long time. In treating bone defects, using a proper bone graft is essential. Among various kinds of bone grafts, bio ceramics alloplastic grafts are considered, owing to their excellent non-toxicity, non- allergenicity, anti-inflammatory, biocompatibility and bio-functionality. The bio-ceramics like Whitlockite (WH: Ca18Mg2(HPO4)2(PO4)12) possess same chemical, structural and biological properties with human bones, have been widely used as bone substitutes. It is the second most abundant mineral in living bone, which can contain 26-58 wt% of bone tissues. In this study, we investigated the biocompatibility, bioactivity and biodegradability of Whitlockite nano powders, by immersing samples in Simulated Body Fluid (SBF) for 3,7,14 and 21 days. The obtained samples were characterized using X-ray Diffraction (XRD), Fourier transform infared spectroscopy (FT-IR) and inductively coupled plasma -optical emission spectrometry (ICP-OES).  Results indicated that, WH nano powders had significantly biocompatibility and biodegradability due to formation of Ca3(PO4)2 , (Ca, Mg)3(PO4)2 and Whitlockite on surface of WH samples. Additionally, the WH nano powders exhibited excellent mineralization ability in vitro with continuously released Ca2+, Mg2+ and HPO42- when immersed in (SBF). Furthermore, the pH changes of both samples were in the range of natural biological pH of the human body, which indicates the appropriate biocompatibility of the samples. However, the stability of whitlockite in SBF is at the highest level in 4<ph<5.< span=""> The results of the ICP analysis of the raw Whitlockite sample showed that about 150 ppm of magnesium ions are released from Whitlockite inside the Simulated Body Fluid during 21 days of immersion, which can provide a part of the body's daily magnesium needs. Also, by examining the weight changes of the samples within the SBF, it will be seen that the weight loss rate of the raw whitlockite sample is concerning 32.11% quite the heat treated whitlockite sample, which indicates the upper biodegradability.</ph<5.<>