Zero-Dimensional Carbon Dots Enhance Bone Regeneration, Osteosarcoma Ablation, and Clinical Bacterial Eradication

Zero-dimensional carbon dots (CD) and their effects on osteogenesis have been rarely studied in bone repair scaffolds. Here, we fabricate a novel CD doped chitosan/nanohydroxyapatite (CS/nHA/CD) scaffold with full potential to promote bone regeneration by a facile freeze-drying method. The CS/nHA/CD scaffolds enhanced cell adhesion and osteoinductivity in rat bone mesenchymal stem cells by up-regulating genes involved in focal adhesion and osteogenesis in vitro, which significantly improved the formation of vascularized new bone tissue at 4 weeks compared to pure CS/nHA scaffolds in vivo. Inspired by the excellent photothermal effect of CD, the scaffolds were applied in tumor photothermal therapy (PTT) under near-infrared (NIR) irradiation (808 nm, 1 W/cm²). The scaffolds significantly inhibited osteosarcoma cell proliferation in vitro and effectively suppressed tumor growth in vivo. Moreover, the CS/nHA/CD scaffolds possessed distinct antibacterial properties toward clinically collected S. aureus and E. coli, and their antibacterial activity was further enhanced under NIR irradiation. This work demonstrates that zero-dimensional CD can enhance the osteogenesis-inducing property of bone repair scaffolds and that CD doped scaffolds have potential for use in PTT for tumors and infections.