Enhanced extraction of hydroxyapatite from bighead carp (Aristichthys nobilis) scales using deep eutectic solvent

Fish-scale waste is rich in biocompatible hydroxyapatite (HAp). In the present study, an environmentally friendly method of extracting HAp from fish-scale waste was developed in an effort to promote environmental sustainability. Deep eutectic solvents (choline chloride/glycerol, 1/2) were used to extract HAp from bighead carp (Aristichthys nobilis) scales. A relatively high extraction rate of 47.67% ± 1.81% was obtained under optimum conditions (70 °C, a solid/liquid ratio of 1/15 g/g and a 2.5 hr extraction time). The obtained HAp was characterized and its purity was determined using Fourier transform infrared spectroscopy and X-ray diffraction, respectively. The chemical composition was performed by energy-dispersive X-ray spectrometry and inductively coupled plasma-optical emission spectroscopy. Its morphology and particle size were observed using scanning electron microscopy and particle size distribution analysis. Thermogravimetric analysis was used to determine its thermal stability. Blood compatibility was determined using a hemolytic test. The results showed that this extraction yielded HAp with the irregular morphology, the higher Ca/P ratio, good thermal stability, and blood compatibility, indicating that the proposed method is an excellent alternative for the improved utilization of fish scale waste. PRACTICAL APPLICATION: Biocompatible hydroxyapatite (HAp) was extracted from fish scale (FS) waste by using an environmentally friendly deep eutectic solvent. The optimized extraction and structure characterization of extracted HAp were investigated in this study. The results showed that the extracted HAp had the irregular morphology, the higher Ca/P ratio, good thermal stability, and blood compatibility, which indicated that the proposed method was an excellent alternative to improving the utilization of FS waste.