Chitosan–Gelatin/Hydroxyapatite Scaffolds With Gelatin Carbon Dots for Application in Bioimages and Photobiostimulation Increase Differentiation of <scp>hFOB</scp> 1.19 Cells

Tissue engineering is a new alternative for the recovery from bone injuries. Nanomaterials are often combined with scaffolds to improve structure, bioactivity, stability, adhesion, and compatibility. Carbon dots (CDs), which are fluorescent carbon nanomaterials with diameters of less than 10 nm, are powerful allies. In this study, we aimed to develop chitosan-gelatin/hydroxyapatite scaffolds and CDs for use in bone tissue engineering. First, we developed two types of CDs based on gelatin and heat-treated them at 200°C for 3 h (CDA) or 4 h (CDB). Both systems were characterized, and CDA exhibited better quantum yield and cytotoxic behavior. Therefore, we selected CDA for the scaffolds. Scaffolds without (CG/HA) and with CDA (CG/HA/CDA) displayed suitable porosities and degradation rates. Based on in vitro tests, we observed that the CD-containing scaffolds presented an excellent cell adhesion rate (94-100%), an indirect cytotoxicity viability of approximately 75%, and a direct cytotoxicity viability of at least 100% at all analyzed times (p < 0.05). Furthermore, alkaline phosphatase (ALP) expression suggested the formation of more mature osteoblasts in CG/HA/CDA. Its association with CDA promotes bioactivity, stability, cell adhesion, and compatibility. We also highlighted the ability of CG/HA/CDA to emit fluorescence for monitoring cell growth during tissue regeneration. These results demonstrated that CDA is highly biocompatible and supports cell growth, which can induce bone tissue regeneration and help treat bone diseases.