Nitrogen doped carbon dots for in vitro intracellular redox modulation via optical stimulation

Carbon dots (CDs) are promising candidates as oxygen photosensitizers, in cancer therapeutic applications due to their high quantum yield, superior chemical and photostability, low cytotoxicity and ease of chemical functionalization/tuning. Nitrogen doping can further improve oxygen photosensitization performance. Besides photodynamic therapy, however, the possibility to finely and remotely regulate the intracellular redox balance by using physical stimuli has been attracting more and more interest not only for nanotheranostic application, but also as a novel, fully biocompatible therapeutic tool. Here, we report on the synthesis of nitrogen-doped CDs by solvothermal methods starting from abundant, bioderived, low-cost precursors, and we characterize their interface with in vitro cultures of human embryonic kidney (HEK-293) cells, a widely accepted model of non-tumoral cells. While not affecting cell proliferation, synthesized CDs efficiently modulate, under visible light and physiological eustress conditions, intracellular calcium ion dynamics and reactive oxygen species concentration, resulting in a 4-fold increase. The reported results may broaden the application of CDs beyond photodynamic therapy, unveiling new opportunities in the field of redox medicine assisted by carbon-based nanomaterials and optical stimulation.