Time-resolved and two-photon emission imaging microscopy of live cells with inert platinum complexes

Abstract

This work explores time-resolved emission imaging microscopy (TREM) for noninvasive imaging and mapping of live cells on a hitherto uncharted microsecond time scale. Simple robust molecules for this purpose have long been sought. We have developed highly emissive, synthetically versatile, and photostable platinum(II) complexes that make TREM a practicable reality. fluorescence microscopy ͉ time-resolved luminescence spectroscopy ͉ transition metal complexes ͉ cyclometalation

A Phosphorescent Iridium(III) Complex‐Modified Nanoprobe for Hypoxia Bioimaging Via Time‐Resolved Luminescence Microscopy

“…Time‐resolved luminescence imaging technology (TRLI) can effectively eliminate the interferences of short‐lived autofluorescence from long‐lived phosphorescence 13, 14, 15, 16, 17, 18, 19, 20. It includes phosphorescence lifetime imaging microscopy (PLIM) and time‐gated luminescence imaging technology (TGLI).…”

Neutral N^C^N terdentate luminescent Pt(ii) complexes: their synthesis, photophysical properties, and bio-imaging applications

“…The investigation of platinum complexes for biological applications concerns mostly monomeric compounds, but aggregates show some important features as well: 19,20 (i) the emitter is shielded from the environment and in particular from dioxygen that could induce quenching; (ii) the rigidity, due to the packing of molecules in determined structures, decreases nonradiative processes; (iii) the reactivity or toxicity of the complexes is diminished by the difficult accessibility of the metal centre; (iv) changes in the excited state nature and properties lead to a bathochromic shift of excitation and emission towards more biologically interesting spectral windows and sometimes to an enhancement of the photophysical properties. In this respect, amongst all luminescent platinum derivatives, those bearing either an N^C^N 22,23 20,28,29 For this purpose, we decided to undertake a systematic study of the bio-imaging and cytotoxicity features of a series of platinum complexes bearing a N^C^N cyclometallated 1,3-di(2-pyridyl)-benzene by varying the molecular hydrophobic/hydrophilic ratio (through the introduction of ethyleneglycol moieties of different lengths) and the ancillary ligand, the incubating medium and the staining concentration. The choice of oligoethyleneglycol chains on the phosphorescent probe was based on their known ability to increase the aqueous solubility and bio-compatibility of luminescent iridium bio-labels.…”

“…[15][16][17][18] Another fast emerging field regarding luminescent Pt(II) complexes is their application as luminescent labels for bioimaging. [19][20][21][22][23] Although fluorescent organic labels are still the leading choice for such applications, [24][25][26] phosphorescent Pt(II) complexes are slowly gaining attention and could outclass organic molecules. In fact, Pt complexes display many advantages such as: (i) a wide emission colour tunability by an adequate choice of the ligands; (ii) a better stability towards photo-and chemical degradation; (iii) a very large Stokes shift that allows the detection of their emission at a much lower energy than the excitation energy; (iv) long-lived luminescent excited states owing to their triplet-manifold nature; (v) emission lifetimes typically two to three orders of magnitude longer than those of classic organic fluorophores.…”

“…For these reasons, molecules displaying a relatively high two-photon absorption cross-section in the NIR are good candidates, and in this respect platinum complexes could be key players. 20,22 † Electronic supplementary information (ESI) available: Additional photophysical data, spectra and bio-imaging studies. See DOI: 10.1039/c4dt03165b ‡ All these authors have contributed equally to this work.…”

Time-resolved luminescence resonance energy transfer imaging of protein–protein interactions in living cells

“…Recently, lanthanide complexes have been developed as probes for live cell imaging applications using time-resolved microscopy with pulsed, near-UV single photon or two photon excitation (25)(26)(27)(28). Time-resolved microscopy in the microsecond domain has also been demonstrated using platinum or palladium complexes (29)(30)(31). However, to date, lanthanide complexes have not been used as LRET donors for intracellular experiments because: (i) suitably bright and photostable complexes were not available; (ii) methods to deliver membraneimpermeant lanthanide complexes from culture medium to the cytoplasm were lacking; and (iii) novel approaches were needed to specifically attach probes to proteins or subcellular structures.…”