CC BY 4.0Settele, SimonSimonSetteleSchrage, AlexanderAlexanderSchrageJung, SebastianSebastianJungMichel, ElenaElenaMichelLi, HanHanLiFlavel, Benjamin S.Benjamin S.FlavelHashmi, A. Stephen K.A. Stephen K.HashmiKruss, SebastianSebastianKrussZaumseil, JanaJanaZaumseil2024-01-302024-01-302024-01-24https://publica.fraunhofer.de/handle/publica/459479https://doi.org/10.24406/publica-252010.1038/s41467-024-45052-110.24406/publica-2520Inorganic pyrophosphate is a key molecule in many biological processes from DNA synthesis to cell metabolism. Here we introduce sp3-functionalized (6,5) single-walled carbon nanotubes (SWNTs) with red-shifted defect emission as near-infrared luminescent probes for the optical detection and quantification of inorganic pyrophosphate. The sensing scheme is based on the immobilization of Cu2+ ions on the SWNT surface promoted by coordination to covalently attached aryl alkyne groups and a triazole complex. The presence of Cu2+ ions on the SWNT surface causes fluorescence quenching via photoinduced electron transfer, which is reversed by copper-complexing analytes such as pyrophosphate. The differences in the fluorescence response of sp3-defect to pristine nanotube emission enables reproducible ratiometric measurements in a wide concentration window. Biocompatible, phospholipid-polyethylene glycol-coated SWNTs with such sp3 defects are employed for the detection of pyrophosphate in cell lysate and for monitoring the progress of DNA synthesis in a polymerase chain reaction. This robust ratiometric and near-infrared luminescent probe for pyrophosphate may serve as a starting point for the rational design of nanotube-based biosensors.encarbon nanotubes and fullerenesfluorescence spectroscopyfluorescent probesjournal article