Characterization of Biocompatible Hydroxyapatite Extracted from Bovine Bones Dissolved in an Ionic Liquid

Abstract

In this study, bovine bone biowaste was dissolved in an ionic liquid (1-ethyl-3-methyl bromide imidazole) to obtain hydroxyapatite (HAp) as a valuable product. The influence of solid–liquid ratio (mass ratios of bovine bone to ionic liquid of 1 : 10, 1 : 20, 1 : 30, 1 : 40, and 1 : 50), dissolution time (2, 3, 4, 5, and 6 h) and dissolution temperature (120, 140, 160, 180, 200, and 220°C) on the yield of HAp was examined. The optimal process parameters determined by an orthogonal test were a solid–liquid ratio of 1 : 25, a dissolution time of 3 h and a dissolution temperature of 220°C. HAp was obtained in a yield of 45%. The extracted HAp was characterized using Fourier transform infrared spectroscopy (FT-IR), X-rays diffraction (XRD), energy dispersive spectrometer (EDS), and scanning electron microscope (SEM). The FT-IR results showed peaks characteristic of HAp, which indicated that extracted HAp had similar components to natural bones. XRD showed that extracted HAp was crystallized. The EDS analysis showed a Ca/P ratio of 1.66 for extracted HAp. Furthermore, the biocompatibility of extracted HAp was assessed through acute toxicity, pyrogen, allergy, and hemolysis. The results showed that extracted HAp was pyrogen free and exhibited mild acute toxicity, slight hypersensitivity, no hemolysis phenomenon, and biocompatibility.