Pondicherry University

This study investigated the sustainable extraction of nano-hydroxyapatite (n-HAP) from Skipjack tuna ( Katsuwonus pelamis ) and Nile tilapia ( Oreochromis niloticus ) bone side streams via thermal calcination at 900 °C for 9 h. The physicochemical and biocompatibility characteristics of the resulting n-HAP were systematically evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray (SEM-EDS), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), and zeta potential measurements. XRD revealed high crystallinity of 76.4% (tuna) and 74.4% (tilapia). TEM confirmed nano-scale structures of 44.9 nm (tuna) and 153.3 nm (tilapia). The Ca/P ratios were 1.72 for tuna and tilapia, and the zeta potential results (−41.1 mV for tuna and −38.3 mV for tilapia) indicated good colloidal stability. FTIR spectra confirmed characteristic phosphate and hydroxyl groups. Both tuna- and tilapia-derived n-HAP exhibited reduced cell viability at 24 h (75.5–80.2%) relative to the control, followed by partial recovery at 72 h (77.5–81.1%). Unlike earlier studies on single fish species, this work presents a comparative evaluation of two different fish bone sources, revealing promising potential for their application in medical scaffolds due to their acceptable preliminary cytocompatibility, stability, and eco-friendly sourcing. • Nano-hydroxyapatite extracted from tuna and tilapia bones via calcination. • Comparative evaluation of physicochemical and biocompatibility profiles. • Stable, non-toxic n-HAP promising for medical scaffolds. • Supports eco-friendly valorization of fish processing side streams.