Extraction and Characterization of Biogenic Hydroxyapatite from Fish Scales via Ultrasound-Assisted Alkaline Hydrolysis

This research provides a thorough investigation into the structural preservation, phase purity, and surface topography of biogenic hydroxyapatite (HA) isolated from natural marine and freshwater waste sources. Utilizing fish scales from Mugil liza (mullet) and Arapaima gigas (pirarucu), the organic collagen matrix was dissolved via an eco-friendly, non-synthetic ultrasound-assisted alkaline hydrolysis route. Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) element profiling identified the biomineral as Calcium-Deficient Hydroxyapatite (CDHA) with a Ca/P ratio of 1.57. X-ray diffraction (XRD) coupled with Rietveld refinement and Reference Intensity Ratio (RIR) models confirmed a 100% phase purity with outstanding thermal structural stability at 1000 °C. Scanning Electron Microscopy (SEM) mapping tracks a well-distributed nanostructured topography (<100 nm) exhibiting interconnected pore networks. These findings validate this multi-source deproteinization extraction for sustainable, high-performance bone tissue engineering applications.