Development and application of fish scale wastes as versatile natural biomaterials

Fish scale is a unique natural biomaterial mainly composed of type I collagen and hydroxyapatite. The highly ordered hierarchical microstructures and composition of fish scales is similar to human hard tissues, which endow its good biocompatibility, degradability, and excellent mechanical properties to fish scales for potential applications including in tissue engineering, biological filling, sewage processing and flexible electronics. However, the practical application of fish scales is relatively limited owing to a lack of commercial value, thus leading to serious problems including waste of materials and pollution of the environment. Therefore, the conversion and reuse of fish scales could significantly reduce the pressure on the natural environment and bring additional commercial value. Herein, we systematically introduce and discuss the composition and highly ordered hierarchical microstructures of fish scales, followed by the summary of their applications in wound healing, bone repair, cell scaffold, cartilage repair, cornea regeneration, electrocatalysis, adsorption, sewage purification, biological filling and bionics. In addition, we also discuss the commercial perspective of fish scales and their derivatives in the near future.