Preliminary Study on Carboxymethyl Chitosan-Based Carbon Dots for Tracing and Promoting Osteogenic Differentiation

Maxillofacial bone defects, a common challenge in oral and maxillofacial surgery, affect over 2 million patients globally each year due to tumor resection, trauma, or infection. Beyond their role in mastication and speech, the structural integrity of jaw bones is critical for facial aesthetics. Current clinical treatments rely on autologous bone grafts, which are limited by donor site morbidity, or allografts with immune rejection risks. Synthetic materials (e.g., titanium alloys, hydroxyapatite) offer mechanical stability but lack bioactivity for efficient osseointegration. Natural polysaccharide-based materials like chitosan have gained attention for their biocompatibility and cell adhesion properties, yet their derivative, carboxymethyl chitosan (CMC), faces limitations such as poor mineralization induction and uncontrollable degradation rates. This study aimed to develop carboxymethyl chitosan-based carbon dots (C-CDs) via citric acid (CA) modification, endowing the material with dual functionalities: temporal regulation of osteogenesis and mineralization through surface polar groups, and cellular tracing via graphitized carbon core fluorescence. The results showed that C-CDs exhibited excellent fluorescence properties and biocompatibility, enhanced ALP activity, and upregulated osteogenic genes (Alp, Runx2, Sp-7, OCN) to promote osteogenic differentiation. In animal studies, the C-CDs group had a significantly higher bone volume fraction (BV/TV) than controls, with histological analysis revealing typical lamellar bone structures, indicating effective promotion of bone regeneration. This innovation addresses the shortcomings of conventional materials for Maxillofacial bone defect repair.