Time-gated luminescence indicators for lysosome and endoplasmic reticulum in living cells based on β-diketonate-europium(III) complexes

Abstract

Lysosome and endoplasmic reticulum (ER) play essential roles for the digestion, synthesis and transportation of biological macromolecules in living cells. For the better visualization and tracking of them, effective luminescence indicators that can specifically locate into them are necessary. In this work, using a visible light-excitable ternary β-diketonate-europium(III) complex, 4,4,5,5,5-pentafluoro-1-(thiophen-2-yl)pentane-1,3-dionate-Eu3+-2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine, as the luminophore, and morpholine and p-toluenesulfonamide moieties that covalently bound to the β-diketonate ligands as organelle-anchoring motifs, two time-gated luminescence (TGL) indicators for lysosome and ER, Lyso-TGL-indicator and ER-TGL-indicator, were designed and synthesized. Two TGL indicators exhibited strong and long-lived emissions at 608 nm, with wide excitation wavelength ranges from UV to visible light (∼320–450 nm, maximum at 396 nm). In addition, two indicators showed low cytotoxicity and excellent lysosome/ER-location performances (Pearson's coefficients >0.97 after being co-localized with commercial lysosome and ER staining agents in cells). These features enabled them to be successfully used for the background-free TGL tracking of lysosomes and ERs in living cells, respectively.