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A Polyoxyethylene‐Substituted Bimetallic Europium Helicate for Luminescent Staining of Living Cells
Author(s) -
Chauvin AnneSophie,
Comby Steve,
Song Bo,
Vandevyver Caroline D. B.,
Thomas Frédéric,
Bünzli JeanClaude G.
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200700883
Subject(s) - hela , luminescence , europium , ligand (biochemistry) , chemistry , bimetallic strip , crystallography , stereochemistry , photochemistry , nuclear chemistry , metal , materials science , in vitro , organic chemistry , biochemistry , receptor , optoelectronics
The homoditopic ligand H 2 L C3 has been designed to form neutral triple‐stranded bimetallic helicates of overall composition [Ln 2 (L C3 ) 3 ]. The grafting of the polyoxyethylene fragments ensures water solubility and also favors cell penetration while being amenable to further derivatization. The ligand p K a values have been determined by spectrophotometric titration and range from 3.5 (sum of the first two) to 10.3. The thermodynamic stability of the helicates is large at physiological pH (logβ 23 in the range 22–23). The ligand triplet state has an adequate energy (0–phonon transition at ≈20 800 cm −1 ) for sensitizing the luminescence of Eu III ( Q =11 %). Analysis of the Eu III emission spectrum points to an overall pseudo D 3 symmetry for the metal environment. No significant effect of [Eu 2 (L C3 ) 3 ] is observed on the viability of several cancerous cell lines (MCF‐7, HeLa, Jurkat, and 5D10). The cell imaging properties of the Eu III helicate are demonstrated for the HeLa cell line by luminescence microscopy. Bright Eu III emission is seen for helicate concentration >50 μ M and after 20–30 min loading time. The helicate stains the cytoplasm and the permeation mechanism is likely to be endocytosis.