Single-molecule sensors based on the selective quenching of the fluorescence of single-walled carbon nanotubes (SWCNTs) have previously been demonstrated for a range of analytes, including NO, H2O2, and other molecules of biological relevance. The strong fluorescence signal of the SWCNTs make these sensors easy to observe and their reversible quenching process makes them stable, reusable, and not sensitive to the photo-bleaching problems of existing small-molecule fluorophores.
In this work, we demonstrate the first use of these sensors to measure intracellular nitric oxide concentrations in A375 melanoma cells, with superior spatio-temporal resolution to previous sensors. The ability of the sensors to measure intracellular NO is confirmed using JS-K, an NO-producing drug developed as a cancer therapeutic.