A pH-resistant Zn(II) sensor derived from 4-aminonaphthalimide: Design, synthesis and intracellular applications

The development and intracellular applications of a water-soluble Zn(II) sensor (WZS) are described. 4-Aminonaphthalimide is used as the fluorophore of WZS for its high photostability, long excitation and emission wavelength, large Stokes' shift and inert response to pH. N,N-Bis(2-pyridylmethyl)ethylenediamine (BPEN), used as a receptor for Zn(II), is attached to the fluorophore through a rigid benzene framework on the imide moiety. Spectroscopic studies indicate that this fluorophore-receptor linking strategy could be used for the development of effective photoinduced electron transfer (PET) sensors. WZS is pH-insensitive and shows high selectivity for Zn(II) against other biologically relevant metal ions. Cellular applications revealed that WZS could be used for the imaging of intracellular Zn(II).