Ditopic boronic acid and imine-based naphthalimide fluorescence sensor for copper(ii)

Copper ions are essential for many biological processes. However, high concentrations of copper can be detrimental to the cell or organism. A novel naphthalimide derivative bearing a monoboronic acid group (BNP) was investigated as a Cu² selective fluorescent sensor in living cells. This derivative is one of the rare examples of reversible fluorescent chemosensors for Cu²  which uses a boronic acid group for a binding site. Moreover, the adduct BNP-Cu² displays a fluorescence enhancement with fructose. The uptake of this novel compound in HeLa cancer cells was imaged using confocal fluorescence microscopy techniques including two-photon fluorescence lifetime imaging microscopy.