Comparative characterisation of mineralised and demineralised fish scales: An approach as scaffolds for tissue engineering

Fish scales have emerged as a promising biomaterial for tissue engineering due to their natural composite structure, which integrates collagen and hydroxyapatite two essential components that are widely used in biomedical applications. This study investigates the potential of fish scales as natural scaffolds by conducting a comparative analysis of their physicochemical, mechanical, and biocompatibility properties, with a particular focus on the role of hydroxyapatite as a mineral phase. The scales were divided into two groups: Group I, which retained the hydroxyapatite-rich mineral layer (Scale I), and Group II, which was demineralized (Scale II). The presence and distribution of hydroxyapatite were confirmed using X-ray diffraction and infrared spectroscopy. Scale I exhibited a contact angle of 65.16 ± 2.08° and surface roughness of 163 nm, while Scale II demonstrated a lower contact angle of 52.38 ± 1.97° and a smoother surface with a roughness of 49 nm. These differences are associated with the presence or absence of hydroxyapatite and its influence on surface energy. The removal of the mineral layer led to a substantial decrease in Young's modulus, with Scale I reaching 2553 MPa, emphasising the structural contribution of hydroxyapatite to the composite material. Thermal analysis further confirmed enhanced stability in Scale I due to the mineral phase. Both types of scales supported cell adhesion and viability in human osteoblast cultures, with Scale II showing slightly enhanced biocompatibility, likely due to the exposure of collagen fibrils. These results demonstrate that fish scales, particularly when demineralized, present favourable biological responses and adequate mechanical integrity, making them viable candidates for bone tissue regeneration.