Probing intracellular oxygen by quenched phosphorescence lifetimes of nanoparticles containing polyacrylamide-embedded [Ru(dpp(SO3Na)2)3]Cl2

Abstract

Methods for measuring O(2) within living cells that rely on luminescent probes are hampered by several factors: local conditions of hydrophobicity, pH, ionic composition, dielectric constant, and photobleaching by free radical species. Use of a polymer-embedded luminophore should minimize these problems. Here we use a Ru(II) coordination complex embedded within 45 nm hydrodynamic diameter nanoparticles, and demonstrate that both phosphorescence intensity and lifetimes are O(2)-sensitive, both in aqueous suspensions and intracellularly (e.g. 4.06 versus 1.55 microseconds under anaerobic or aerobic conditions, respectively). Electroporation is necessary for incorporation of the nanoparticles into yeasts: it is more effective with the fission yeast, Schizosaccharomyces pombe, than for the budding yeast, Saccharomyces cerevisiae. However, electroporation was not required for particle uptake into a cultured human cell-line (mammary adenosarcoma MCF-7), although the intracellular distribution of the probe is more general to intracellular compartments when electroporation is employed. These procedures did not compromise vitality of cells over periods of 6 h, as judged by retention of structural characteristics evident in Nomarski interference or confocal microscopy images. Spatial resolution of intracellular structures defined by nanoparticle phosphorescence intensity imaging indicates potential usefulness of the application of lifetime imaging techniques for mapping of intracellular O(2) distributions.

Structure–Photoluminescence Quenching Relationships of Iridium(III)–Tris(phenylpyridine) Complexes

“…[18] This strategy was not successful in the case of the open complexes; they were synthesized in two steps. [21] First the dichlorido-bridged dimer was obtained by reaction of the desired ligand (7,10) All the intermediates and the target complexes were characterized by IR and NMR ( 1 H and 13 C) spectroscopy and mass spectrometry, and the characteristic data are reported in the Experimental Section and in the Supporting Information. Complexes 1-4 show only one set of NMR spectroscopic signals for the three phenylpyridine ligands, which proves that the threefold symmetry expected for fac complexes is maintained.…”

“…[5][6][7][8] Moreover, the interaction of the excited states of transition-metal complexes with dioxygen (which results in the quenching of luminescence and the generation of highly reactive species like singlet oxygen and superoxide radical anion) has received increasing interest due to the possible realization of diagnostic and therapeutic agents. [9][10][11][12][13][14] Despite the studies directed towards understanding the theoretical relationship between structure and optical properties, [15,16] little is known about the structure-photoluminescence quenching relationship (SPQR) of these complexes. Transition-metal complexes with a cagelike ligand structure show a remarkable decrease in oxygen quenching.…”

Oxygen‐Sensing Methods in Biomedicine from the Macroscale to the Microscale

“…[193,194] Cell-uptake studies with oxygen-sensor-loaded nanoparticles formed by different polymeric materials indicated that although the nanoparticle interior can provide sufficient shielding from excessive oxygen quenching, the lack of as urface cell-targeting layer can result in inefficient cell internalization or increased toxicity. [195,196] To enhance cellular uptake,Koo Lee et al recenly co-embedded Oxyphor G2 and an oxygen-insensitive dye (Alexa 647 dextran or HiLyte 680 SE) into polyacrylamide hydrogel nanoparticles bearing different targeting peptides. [197] Ther esulting nanoparticles were non-toxic,m embrane-permeable,a nd tumor-specific ratiometric nanosensors.…”

“…[207] Coupling poly(lactic acid) (PLA) polymers of different chain lengths to the boron complex resulted in polymers whose fluorescence/ phosphorescence ratio was modulated by changes in the molecular weight. The nanoparticles that were made from the polymer exhibited balanced fluorescence and phosphorescence intensities, and served as ratiometric imaging agents that enabled the in vivo quantification of improved uptake by electroporation [195] Oxyphor R2/polysaccharide embryo chorioallantoic membranes of chicks toxicity decreases embryo viability [196] Oxyphor R2, Alexa647, or HiLyte 680 SE/ polyacrylamide hydrogel A549, C6 glioma, and MCF-7 cells ratiometric, coated with targeting peptides [197] PtTFPP/Eudragit RL-100 (NanO2) mammalian and murine cells [a,b] cationic, non-specific endocytosis [ 198] PtTFPP/PFO, Eudragit RL-100 (MM2) MEF cells, embryonicr at neurosphere cultures two-photon-excited, FRET-activated, multiple detection modalities [199] PtTFPP/PFO, PMMA-MA( PA2) MEF, PC12 cells, 3D rat brain slices anionic, ratiometric, two-photon excited [200] PtOEP/PFO,P DHF J774 A1 murine cells FRET-activated, brightly emissive [205] [Ru(dpp) 3 . .…”

Intracellular oxygen: Similar results from two methods of measurement using phosphorescent nanoparticles

“…Exceptionally longlived°uorescent states such as this have been employed for O 2 -mapping in living cells, e.g., in cultured cells of mouse liver by the use of quantitative°uorescence microscopy, 24 and in Amoeba proteus. 25 The even longer lifetimes provided by O 2 -quenchable phosphorescent luminophores, [26][27][28][29] together with their other desirable photophysical properties, [30][31][32][33][34][35] make them substances of choice for a burgeoning body of applications.…”