title: Combined two-photon excitation and d→f energy transfer in a water-soluble Ir(III)/Eu(III) dyad: two luminescence components from one molecule for cellular imaging.
abstract: The first example of cell imaging using two independent emission components from a dinuclear d/f complex is reported. A water-stable, cell-permeable Ir(III) /Eu(III) dyad undergoes partial Ir→Eu energy transfer following two-photon excitation of the Ir unit at 780 nm. Excitation in the near-IR region generated simultaneously green Ir-based emission and red Eu-based emission from the same probe. The orders-of-magnitude difference in their timescales (Ir ca. μs; Eu ca. 0.5 ms) allowed them to be identified by time-gated detection. Phosphorescence lifetime imaging microscopy (PLIM) allowed the lifetime of the Ir-based emission to be measured in different parts of the cell. At the same time, the cells are simultaneously imaged by using the Eu-based emission component at longer timescales. This new approach to cellular imaging by using dual d/f emitters should therefore enable autofluorescence-free sensing of two different analytes, independently, simultaneously and in the same regions of a cell.
authors.affiliation: Department of Chemistry, University of Sheffield, Sheffield S3 7HF (UK).
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Baggaley
authors.forename: Deng-Ke
authors.initials: DK
authors.lastname: Cao
authors.forename: Daniel
authors.initials: D
authors.lastname: Sykes
authors.forename: Stanley W
authors.initials: SW
authors.lastname: Botchway
authors.forename: Julia A
authors.initials: JA
authors.lastname: Weinstein
authors.forename: Michael D
authors.initials: MD
authors.lastname: Ward
mesh_terms: D002460:Cell Line; D004735:Energy Transfer; D005063:Europium / Q000032:analysis*; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D007495:Iridium / Q000032:analysis*; D049449:Luminescence; D049408:Luminescent Agents / Q000032:analysis*; D008853:Microscopy / Q000379:methods; D061848:Optical Imaging / Q000379:methods; D017785:Photons; D012995:Solubility; D014867:Water / Q000737:chemistry
chemical_list: D049408:Luminescent Agents; D014867:Water; D007495:Iridium; D005063:Europium
keywords: energy transfer; europium; imaging agents; iridium; luminescence