NIRvana in Bioimaging: Crafting Biocompatible Graphene Quantum Dots from Everyday Precursors.

Graphene quantum dots (GQDs) have gained attention in the bioimaging community due to their biocompatibility and ability to enhance imaging depth in the near-infrared (NIR) region. Developing a simple and reproducible synthesis method for biocompatible NIR-fluorescent GQDs from a variety of precursors remains a critical task. Herein, we synthesized eleven GQD structures capable of NIR fluorescence via bottom-up caramelization of precursor materials including ascorbic acid, chitosan, citric acid-urea, dextran, glucose, glucosamine hydrochloride, hyaluronic acid, l-glutamic acid, polyethylene glycol (PEG), sodium cholate, and sodium citrate. All synthesized GQDs exhibited excellent biocompatibility at concentrations up to 1 mg/mL, as evaluated by MTT assays, confirming their suitability for therapeutic applications. The GQDs were successfully tracked by their NIR fluorescence in in-vitro bioimaging and demonstrated effective cellular internalization in the HEK-293 cell line, maximized at 12 hours. This work presents a comprehensive study of a scalable and cost-effective process to synthesize NIR-emissive, highly biocompatible GQDs from eleven precursor materials, while also analyzing their optical properties. Owing to their strong biocompatibility and photostable NIR emission, the GQDs developed here represent promising candidates for future clinical fluorescence imaging applications.