Quantitative and real-time effects of carbon quantum dots on single living HeLa cell membrane permeability

The interaction between carbon quantum dots (CQDs) and a single living cell was explored in real time. Here, we provide the quantitative data on the permeability of the HeLa cell membrane in the presence of CQDs with different surface functional groups (CQDs terminated with -OH/-COOH (CQD-OH), -PEG (CQD-PEG), and -NH 2 (CQD-NH 2 )). Although these CQDs have very low toxicity towards HeLa cells, they still increase the cell membrane permeability by 8%, 13%, and 19% for CQD-PEG, CQD-OH, and CQD-NH 2 , respectively, and this kind of permeability was irreversible. These observations are valuable for promoting the bio-applications of carbon nanostructures in living systems. Low toxicity and biocompatible CQDs with different surfaces show different effects on the increasing cell membrane permeability.