Synergistic effects of sonication duration and calcination temperature on the structural, physicochemical and bioactivity of biogenic nano-hydroxyapatite from scallop shells for bone repair applications

This study explores the synergistic effects of sonication duration and calcination temperature on the synthesis of biogenic nano-hydroxyapatite from scallop shell waste for bone repair applications. The synthesis involved wet ball milling and sonochemical treatment at 30 and 60 min of sonication, followed by calcination at 900 °C, 1000 °C, and 1100 °C. Increasing the calcination temperature led to larger crystallite size due to the effect of coalescence phenomenon and greater unit-cell volume. A sonication duration of 60 min promoted the formation of β-tricalcium phosphate (β-TCP). The combination of 60 min of sonication and calcination at 900 °C produced hydroxyapatite with the smallest crystallite size with hexagonal structure, lowest unit-cell volume, and an average particle size of 68.4 nm. Cytotoxicity tests confirmed the material's biocompatibility, with osteoblast (MC3T3-E1) cell viability exceeding 70 %. Antibacterial tests revealed weak inhibition against Escherichia coli and Staphylococcus aureus, suggesting potential for further enhancement. Overall, scallop shell waste provides a sustainable, low-cost source for producing bioactive nano-hydroxyapatite, supporting the eco-friendly development of bone regeneration materials. Future work should optimize antibacterial performance and assess in vivo efficacy.