Effect of Calcination Time on Bovine-Derived Hydroxyapatite as Bone Implant Material: An <em>In Vitro </em>Study

Abstract

Bone fracture incidence has been increasing, according to recent studies. For a fracture to heal, orthopedic implants are usually employed. One of the bioceramics used is hydroxyapatite (HAp), which has a similar chemical structure with bone mineral and is biocompatible, bioactive as well as non-toxic to the human body. Current methods of HAp synthesis are mostly still toxic to the human body and expensive. Hydroxyapatite originated from natural resources can provide more favorable materials. The purpose of this study is to characterize HAp extracted from bovine bone calcination at 850°C for various holding times as bone implant material. The toxicity of the bovine-derived HAp is also assessed. Prepared bovine bones were subjected to calcination at 850°C over various holding times. The characterization was carried out with thermogravimetric analysis (TGA) instrument followed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and Fourier-Transform Infrared Spectroscopy (FT- IR). The toxicity of the bovine HAp was assessed using MTT (3-[4, 5-dimethyl-thiazol-2-yl-]-2, 5-diphenyltetrazolium bromide) assay. Each of the parameters was compared between the HAp extracted from bovine and the commercial HAp. Analysis of the phase, purity, and crystallinity showed that the bovine-derived HAp was similar to the standard HAp. Crystal agglomeration was observed at increased calcination time. The optimal holding time of 5 hours was demonstrated through the closest Ca/P ratio (1.679) to the stoichiometric HAp (Ca/P ratio = 1.67) in EDX analysis. The toxicity test using the MTT assay showed that the viabilities of CPAE cells treated with bovine HAp were well above 60% (non-toxic threshold). In conclusion, hydroxyapatite produced from bovine bone calcination at 850°C with 5 hours of holding time has the characteristics which are similar to the commercial HAp. This natural HAp has proven to be non-toxic and also cost-effective.