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Molecules 2016, 21(10), 1382;

Towards Water Soluble Mitochondria-Targeting Theranostic Osmium(II) Triazole-Based Complexes

Department of Chemistry, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, UK
Department of Chemistry, Dainton Building, University of Sheffield, Sheffield S3 7HF, UK
Academic Unit of Molecular Oncology, Sheffield Institute for Nucleic Acids (SInFoNiA), Department of Oncology and Metabolism, University of Sheffield, Beech Hill Road, Sheffield S10 2RX, UK
Author to whom correspondence should be addressed.
Academic Editor: James Crowley
Received: 29 September 2016 / Revised: 11 October 2016 / Accepted: 12 October 2016 / Published: 18 October 2016
(This article belongs to the Special Issue Recent Advances in CuAAC Click Chemistry)
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The complex [Os(btzpy)2][PF6]2 (1, btzpy = 2,6-bis(1-phenyl-1,2,3-triazol-4-yl)pyridine) has been prepared and characterised. Complex 1 exhibits phosphorescence (λem = 595 nm, τ = 937 ns, φem = 9.3% in degassed acetonitrile) in contrast to its known ruthenium(II) analogue, which is non-emissive at room temperature. The complex undergoes significant oxygen-dependent quenching of emission with a 43-fold reduction in luminescence intensity between degassed and aerated acetonitrile solutions, indicating its potential to act as a singlet oxygen sensitiser. Complex 1 underwent counterion metathesis to yield [Os(btzpy)2]Cl2 (1Cl), which shows near identical optical absorption and emission spectra to those of 1. Direct measurement of the yield of singlet oxygen sensitised by 1Cl was carried out (φ (1O2) = 57%) for air equilibrated acetonitrile solutions. On the basis of these photophysical properties, preliminary cellular uptake and luminescence microscopy imaging studies were conducted. Complex 1Cl readily entered the cancer cell lines HeLa and U2OS with mitochondrial staining seen and intense emission allowing for imaging at concentrations as low as 1 μM. Long-term toxicity results indicate low toxicity in HeLa cells with LD50 >100 μM. Osmium(II) complexes based on 1 therefore present an excellent platform for the development of novel theranostic agents for anticancer activity. View Full-Text
Keywords: triazole; osmium; photophysics; complexes; ligands; anticancer; oxygen sensitizer triazole; osmium; photophysics; complexes; ligands; anticancer; oxygen sensitizer

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Omar, S.A.E.; Scattergood, P.A.; McKenzie, L.K.; Bryant, H.E.; Weinstein, J.A.; Elliott, P.I.P. Towards Water Soluble Mitochondria-Targeting Theranostic Osmium(II) Triazole-Based Complexes. Molecules 2016, 21, 1382.

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