Functionalized Carbon Dots from Bio-Based Precursors as Promising Fluorescent Probes for Cancer Cell Imaging

This study reports the microwave-assisted synthesis and surface modification of carbon quantum dots (CQDs) from natural precursors and their evaluation as fluorescent probes for cancer cell visualization. CQDs were obtained using amino-glucose as the carbon source and betaine, marine collagen, or dopamine as surface modifiers. Further functionalization with 7-amino-4-(trifluoromethyl)coumarin enhanced their fluorescence properties. Spectroscopic analyses confirmed successful surface modification, with coumarin-modified CQDs displaying a strong emission peak at ~500 nm and approximately 1.5-fold higher fluorescence intensity compared to unmodified CQDs. Cytotoxicity testing on MG-63 osteosarcoma cells showed cell viabilities above 80% for selected samples, fulfilling ISO 10993-5 criteria for non-toxicity. In vitro bioimaging of astrocytoma 1321N1 cells demonstrated bright and uniform intracellular staining, confirming effective cellular uptake. Compared with the literature reports of green-synthesized CQDs, our results indicate comparable or superior fluorescence performance and similar levels of biocompatibility. These findings highlight the potential of surface-engineered CQDs as biocompatible nanoprobes for cancer diagnostics and represent an initial step toward their application in the detection of circulating tumor cells (CTCs).