Zn2+-enhanced Ru (II) photoluminescence directed by double-clamp structural ligand for selective Zn2+ sensing and live-cell imaging

Abstract

A novel water-soluble, visible-light-excitable, fluorescence enhancement sensor (λex = 450 nm), [Ru (PYPZA-tBuDO3A) (bipy)2]2+, has been synthesized and characterized, which efficiently recognize Zn2+ ions without interference from other biologically relevant metal ions, anions, amino acids, small biomolecules or pharmaceutical molecules in phosphate buffered saline (PBS, pH = 7.0). The detection has high sensitivity (detection limit = 5.3533 × 10-9 mol/L) for Zn2+ ions owning to the formation of 1:1 binding with a large binding constant (K = 2.1586 × 105 M-1). Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were performed to determine the mechanism for changes of photophysical properties illustrating fluorescence increase response to Zn2+ ions. The [Ru (PYPZA-tBuDO3A) (bipy)2]2+ also exhibits excellent membrane permeability and negligible cytotoxicity, and can be applied to sense intracellular Zn2+ in live human cells.