Organelle-selective di-(2-picolyl)amine-appended water-soluble fluorescent sensors for Cu(II): Synthesis, photophysical and in vitro studies

A novel water-soluble fluorescent naphthalimide derivative as a sensor for Cu(II) has been synthesized. The sensor, conjugated with DPA (as the Cu(II)-binding moiety) and TPP (as the mitochondrial-targeting moiety) was further decorated with a galactose unit at the fluorophore's terminal using the click reaction. Although confocal fluorescence imaging revealed that probe 1 was not localized in mitochondria, and was neither quenched under Cu-overloading conditions, probe 1 did exhibit a high selectivity for Cu(II) ions over various metal ions in HEPESbuffered solutions. Furthermore the fluorescence was dramatically quenched upon the addition 1 equivalent of Cu(II), and the response was stable in the range of pH 6-10.