Self-assembled supramolecular nanoprobes for ratiometric fluorescence measurement of intracellular pH values.

Self-assembly of small building blocks into functional supramolecular nanostructure has opened prospects for the design of novel materials. With this molecular engineering strategy, we have developed self-assembled supramolecular nanoprobes (SSNPs) for ratiometric fluorescence measurement of pH values in cells. The nanoprobes with a diameter of ∼30 nm could be formulated just by mixing pH-sensitive adamantane-fluorescein (Ad-F) and pH-insensitive adamantane-Rhodamine B (Ad-R) with ß-cyclodextrin polymer (poly-ß-CD) at one time. The nanoprobes with good biocompatibility have been successfully applied to measure intracellular pH in the pH range of 4-8 and estimate pH fluctuations associated with different stimuli in cells. Moreover, we expect that this self-assembled approach is applicable to the construction of nanoprobes for other targets in cells just by replacing the respective indicator dyes with relevant indicators.