Physicochemical Characterization of the Salmon Bone Hydroxyapatite and Collagen Mixture

Objective: To develop and characterize a particulate biomaterial composed of hydroxyapatite derived from salmon bone and bovine type I collagen (HAPS/COL), and to evaluate whether different inorganic–organic ratios influence its physicochemical properties. Materials & Methods: Biomaterials were produced using three HAPS/COL proportions (70/30, 80/20, and 90/10). Physicochemical characterization included pycnometry, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). Results: Pycnometry showed densities close to that of pure hydroxyapatite, with only slight decreases attributable to collagen content. SEM-EDX images showed comparable surface morphologies characterized by hydroxyapatite particulates surrounded by collagen fibers. Ca/P ratios were slightly higher than the stoichiometric value of hydroxyapatite. XRD confirmed hydroxyapatite as the dominant crystalline phase across all formulations, with no evidence of phase alteration. TGA revealed mass losses of 2.75%, 1.90%, and 1.60% for the 70/30, 80/20, and 90/10 mixtures, respectively, with consistent mass loss-to-collagen ratios of approximately 0.09 for the 70/30 and 80/20 formulations, confirming proportional organic phase degradation. Conclusions: The three HAPS/COL ratios produced biomaterials with highly similar physicochemical profiles, indicating that within the tested range, the proportion of hydroxyapatite and collagen does not substantially alter material structure, composition, or thermal behavior. These findings confirm the successful manufacture of a stable HAPS/COL blend, allowing the use of efficient quantities of collagen, thus minimizing the costs associated with its purchase.