Carbon dots as multifunctional platform for intracellular pH sensing and bioimaging. In vitro and in vivo studies

In the present work we have obtained carbon dots (CDs) from glutathione and modified their surface with both beta-Cyclodextrin and methyl-3-(4-(2-(5-((methylsulfonyl)oxy)pentyl)-1,3-dioxo -2,3-dihydro- 1H-benzo[de]iso-quinolin-6-yl)piperazin-1-yl)propanoate (FP), a pH-sensitive molecule. beta-Cyclodextrin acted as a glucose source, which facilitated the entrance of the CDs within the cells and, eventually, can be used as drug-carrier to deploy bioactive compounds in the cytoplasm. FP fluorescence varied according to the pH of the medium and can be used to distinguish cancer cells due to the Warburg effect Cytotoxicity studies revealed that, contrarily to simple CDs, carbon nanodots modified with beta-cyclodextrins had an impact in cell cycle phase distribution, with no alterations of cell morphology. Likewise, CDs modified with beta-cyclodextrin and FP can be used to distinguish cancer cells from non-cancerous ones due to an increase in fluorescent emission. Furthermore, this modified CDs can also be used to obtain high contrast in vitro images as well as in vivo images. These results demonstrate the potential applications of the synthetized nanoparticles both in bioimaging and as theranostic sensor and actuator.