The dinuclear photo-oxidizing RuII complex [{Ru­(TAP2)}2(tpphz)]4+ (TAP = 1,4,5,8- tetraaza­phenanthrene, tpphz = tetrapyrido­[3,2-a:2′,3′-c:3″,2′′-h:2‴,3′′′-j]­phenazine), 1 4+, is readily taken up by live cells localizing in mitochondria and nuclei. In this study, the two-photon absorption cross section of 1 4+ is quantified and its use as a two-photon absorbing phototherapeutic is reported. It was confirmed that the complex is readily photoexcited using near-infrared, NIR, and light through two-photon absorption, TPA. In 2-D cell cultures, irradiation with NIR light at low power results in precisely focused phototoxicity effects in which human melanoma cells were killed after 5 min of light exposure. Similar experiments were then carried out in human cancer spheroids that provide a realistic tumor model for the development of therapeutics and phototherapeutics. Using the characteristic emission of the complex as a probe, its uptake into 280 μm spheroids was investigated and confirmed that the spheroid takes up the complex. Notably TPA excitation results in more intense luminescence being observed throughout the depth of the spheroids, although emission intensity still drops off toward the necrotic core. As 1 4+ can directly photo-oxidize DNA without the mediation of singlet oxygen or other reactive oxygen species, phototoxicity within the deeper, hypoxic layers of the spheroids was also investigated. To quantify the penetration of these phototoxic effects, 1 4+ was photoexcited through TPA at a power of 60 mW, which was progressively focused in 10 μm steps throughout the entire z-axis of individual spheroids. These experiments revealed that, in irradiated spheroids treated with 1 4+, acute and rapid photoinduced cell death was observed throughout their depth, including the hypoxic region.

A detailed study on the uptake and antimicrobial activity of a RuII theranostic complex with wild-type S. aureus, MRSA, and other mutants has identified the specific resistance mechanisms that Gram-positive bacteria display against this lead.

The synthesis of a new dinuclear complexes containing linked Ru II (dppz) and Re I (dppz) moieties is reported. The photophysical and biological properties of the new complex, which incorporates a N,N'-bis(4-pyridylmethyl)-1,6-hexanediamine tether ligand, are compared to a previously reported Ru II /Re I complex linked by a simple dipyridyl alkane ligand. Although both complexes bind to DNA with similar affinities, steady state and time resolved photophysical studies reveal that the nature of the linker affects the excited state dynamics of the complexes and their DNA photocleavage properties. Quantum based DFT calculations on these systems offers insights into these effects. Whilst both complexes are live cells permeant, their intracellular localization are significantly affected by the nature of the linker. Notably, one of the complexes displayed concentration dependent localization and possesses photophysical properties that are compatible with SIM and STED nanoscopy. This allowed the dynamics of its intracellular localization to be tracked at super resolutions.

Drug resistance to platinum chemotherapeutics targeting DNA often involves abrogation of apoptosis, and has emerged as a significant challenge in modern, non-targeted chemotherapy. Consequently, there is great interest in the anti-cancer properties of metal complexes-particularly those that interact with DNA-and mechanisms of consequent cell death. Herein we compare a parent cytotoxic complex [Ru(phen)2(tpphz)] 2+ [phen = 1,10-phenanthroline, tpphz = tetrapyridyl [3,2-a:2',3'-c:3'',2''-h:2''',3'''-j] phenazine], with a mononuclear analogue with modified intercalating ligand, [Ru(phen)2(taptp)] 2+ ,[taptp = 4,5,9,18-tetraazaphenanthreno[9,10-b] triphenylene], and two structurally related di-nuclear, tpphz-bridged, heterometallic complexes, RuRe and RuPt. These changes result in a switch from intercalation to groove binding DNA interaction, concomitant reduction in cytotoxic potency, but no significant change in relative cytotoxicity toward platinum-resistant A2780CIS cancer cells, indicating that DNA interaction mode is not critical for the mechanism of platinum resistance. All variants exhibited a light-switch effect, which for the first time, was exploited to investigate timing of cell death by live cell microscopy. Surprisingly, cell death occurred rapidly as a consequence of oncosis, characterized by loss of cytoplasmic volume control, absence of significant mitochondrial membrane potential loss, and lack of activation of apoptotic cell death markers. Importantly, a novel, quantitative proteomic analysis of the A2780 cell genome following exposure to either mononuclear complex reveals changes in protein expression associated with global cell responses to oxidative stress, and DNA replication/repair cellular pathways. This combination of a multiple targeting modality and induction of a non-apoptotic death mechanism makes these complexes highly promising chemotherapeutic cytotoxicity leads.

Herein we report the separation of the three stereoisomers of the DNA light-switch compound [{Ru-(bpy) 2 } 2 (tpphz)] 4+ (tpphz = tetrapyrido[3,2-a:2′,3′-c:3″,2″h:2‴,3‴-j]phenazine) by column chromatography and the characterization of each stereoisomer by X-ray crystallography. The interaction of these compounds with a DNA octanucleotide d(GCATATCG).d(CGATATGC) has been studied using NMR techniques. Selective deuteration of the bipyridyl rings was needed to provide sufficient spectral resolution to characterize structures. NMR-derived structures for these complexes show a threading intercalation binding mode with slow and chirality-dependent rates. This represents the first solution structure of an intercalated bis-ruthenium ligand. Intriguingly, we find that the binding site selectivity is dependent on the nature of the stereoisomer employed, with Λ Ru II centers showing a better intercalation fit.