N-Doped Carbon Dot-Based Nanoconjugates with Simultaneous Generation of Nitric Oxide and Singlet Oxygen for Phototherapeutic Applications

Nitric oxide (NO) and singlet oxygen (1O2) represent two of the most intriguing agents for unconventional phototherapeutic applications in cancer. In this contribution, N-doped carbon dots (NCDs) with strong absorption in the biocompatible green region have been synthesized and covalently decorated with an otherwise blue-light-activatable NO photodonor (NOPD), leading to a nanoconjugate ca. 3.5 nm in diameter. The NCD core of the nanoconstruct acts as a green light antenna, permitting the release of NO from the NOPD by an intramolecular photoinduced electron transfer, with an improvement of more than 100 nm in the excitation wavelength. Simultaneously, green light excitation generates 1O2 by collisional energy transfer with molecular oxygen. Due to its emissive properties, the nanoconjugate can be visualized in 9L/LacZ brain cancer cells, where it localizes mainly in the cytoplasm. Amplified mortality of cancer cells is observed upon green light irradiation due to the mutual photodynamic action of NO and 1O2