A Highly Selective and Efficient Copper(II) - %26quot;Turn-On%26quot; Fluorescence Imaging Probe for L-Cysteine

作者：Maheshwaran Duraiyarasu; Nagendraraj Thavasilingam; Manimaran Paramasivam; Ashokkumar Balasubramaniem; Kumar Mukesh; Mayilmurugan Ramasamy

来源：European Journal of Inorganic Chemistry, 2017, 2017(6): 1007-1016.

DOI：10.1002/ejic.201601229

• Copper
• Amino acids
• Cell imaging
• Fluorescent probes
• N ligands

A simple copper(II) complex of the anthracenylappended terpyridine ligand 4'-(anthracen-9-yl)-2,2': 6', 2''-terpyridine (L), [Cu(L)Cl-2] (1, ESI-MS, m/z = 507.08), is reported as a highly selective " turn-on" optical imaging probe for L-cysteine. Probe 1 shows a Cu-II/Cu-I redox potential [E-1/2 = -0.194 V versus normal hydrogen electrode (NHE)] within a biologically viable range. The copper center in 1 adopts a square-pyramidal geometry (tau = 0.0851), and the Cu-N-py bond (1.970 angstrom) of the middle pyridine (py) ring is shorter than the other two Cu-N-py bonds (2.069 and 2.040 angstrom). The Cu-Cl bonds (2.444 and 2.027 angstrom) are labile enough to be replaced by solvent molecules. The squarebased geometry is further supported by the A(II) value of 156.8 x 10(-4) cm(-1) determined by electron paramagnetic resonance (EPR) spectroscopy at 70 K. The d-d transition of 1 in acetonitrile/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (acetonitrile/HEPES) buffer at pH 7.34 appears at lambda = 760 nm (epsilon = 198 M-1 cm(-1)), and the ligand-based transitions are observed at lambda = 327-384 nm. The ligand shows strong fluorescence at lambda = 430 nm with a quantum yield of 11 %, but its emission intensity is completely quenched on coordination with Cu2+ ions, as in 1. Probe 1 detects L-cysteine selectively through turn-on fluorescence intensity at lambda(em) = 431 nm with a limit of detection of 1.9 x 10(-8) M at pH 7.34. Interestingly, probe 1 is able to visualize exogenously added L-cysteine in Henrietta Lack cervical cancer (HeLa) cells, human liver hepatocellular carcinoma (HepG2) cells, and human embryonic kidney 293 (HEK293) cells under identical conditions at pH 7.4 in confocal microscopy imaging.

• 出版日期2017-2-10