Boron-Doped Carbon Dots for Organelle Labeling and Mitochondrial Bioimaging

Carbon dots (CDs) are promising fluorescent nanomaterials with great application potential in bioimaging and organelle-targeted diagnostics. This study compares nitrogen-doped (N-CDs) and boron-nitrogen co-doped CDs (BN-CDs) in normal NIH3T3 fibroblasts and KRAS-transformed cells.

CDs were synthesized via a microwave-assisted method. Their fluorescence, cytocompatibility, and intracellular localization were evaluated using confocal microscopy, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, and organelle colocalization. Cellular metabolism was assessed by Seahorse analysis. Oxidative stress and cAMP levels were pharmacologically modulated.

BN-CDs exhibited stronger intracellular fluorescence than N-CDs, indicating enhanced uptake and imaging performance, with no cytotoxicity up to 100 µg/mL. They localized to multiple organelles, particularly mitochondria. However, fluorescence was significantly reduced in KRAS-transformed cells despite similar mitochondrial mass. BN-CDs did not affect mitochondrial respiration or glycolytic activity. Induced oxidative stress or elevated cAMP in normal cells reduced BN-CD fluorescence.

Boron doping improves N-CD imaging properties without affecting cell viability or metabolism. Reduced fluorescence in KRAS cells is associated with altered intracellular conditions, suggesting that BN-CDs could be used to discriminate between normal and cancer cells.