Insights into glucose-derived carbon dot synthesis via Maillard reaction: from reaction mechanism to biomedical applications

Carbon dots (CDs) are versatile nanomaterials that are considered ideal for application in bioimaging, drug delivery, sensing, and optoelectronics owing to their excellent photoluminescence, biocompatibility, and chemical stability features. Nitrogen doping enhances the fluorescence of CDs, alters their electronic properties, and improves their functional versatility. N-doped CDs can be synthesized via solvothermal treatment of carbon sources with nitrogen-rich precursors; however, systematic investigations of their synthesis mechanisms have been rarely reported. In this study, we developed a method to synthesize N-doped CDs using the Maillard reaction with glucose and ethanolamine as precursors (namely, G-CDs). Comprehensive characterization of these G-CDs revealed the successful incorporation of nitrogen- and glucose-like functionalities. The optical properties and electronic band structures of G-CDs were analyzed using transient absorption and time-resolved photoluminescence spectroscopy. The prepared G-CDs demonstrated near-infrared photoluminescence, low cytotoxicity, glucose transporter-facilitated cellular uptake, and effective heat generation under an 808-nm laser. Particularly, the cellular uptake of G-CDs was reduced by up to 25% after preincubation with a Glut1 inhibitor. These features are suitable for in vitro biological imaging and photothermal therapy in prostate cancer cells. This paper highlights the potential of G-CDs in clinical applications owing to their multicolor emission, photothermal conversion functionality, and versatile surface structure.