Simultaneous synthesis of hydroxyapatite/chitosan composite from crab shells and its polycaprolactone-blended...

Although the hydroxyapatite-chitosan reinforced poly(ε-caprolactone) composite (PCL/HA-CS) is vital for bone regeneration, it is still predominantly synthesized from various non-biological sources, while natural bioresources, such as crab shell, containing essential precursors, are discarded as waste, causing environmental pollution. Here, we present a sustainable strategy to fabricate bone scaffolds by directly converting crab shells into a HA-CS composite via a one-pot process, followed by blending with PCL. The resulting HA-CS composite, containing 78.37% nano-sized HA, exhibited strong antibacterial activity without cytotoxic effects, with minimum inhibitory concentrations of 2.5 mg mL^-1 and 5 mg mL^-1 for S. aureus and E. coli, respectively, and corresponding minimum bactericidal concentrations of 5 mg mL^-1 and 10 mg mL^-1. When combined with PCL, the biogenic material demonstrated balanced mechanical strength, biocompatibility, and excellent mineralization under in vitro conditions. A formation mechanism was also proposed, in which the amine groups of CS interact with HA, while residual hydroxyl groups form interfacial bonds with PCL, enabling uniform distribution of HA-CS within the polymer matrix. Moreover, the biodegradation rate (ν) of PCL/HA-CS during the first four weeks could be linearly tuned by adjusting the HA-CS content, following a linear relationship: ν (%/day) = 0.0108 [HA-CS] (%) + 0.1133. This controllability enables better synchronization between scaffold degradation and new bone formation, addressing a major limitation of conventional PCL-based scaffolds. Overall, crab shell waste offers a promising and eco-friendly route to generate high-performance scaffolds for bone tissue engineering.