From Chemotherapy to Phototherapy - Changing the Therapeutic Action of a Metallo-Intercalating RuII -ReI Luminescent System by Switching its Sub-Cellular Location

The synthesis of a new heterodinuclear ReI RuII metallointercalator containing RuII (dppz) and ReI (dppn) moieties is reported. Cell-free studies reveal that the complex has similar photophysical properties to its homoleptic M(dppz) analogue and it also binds to DNA with a similar affinity. However, the newly reported complex has very different in-cell properties to its parent. In complete contrast to the homoleptic system, the RuII (dppz)/ReI (dppn) complex is not intrinsically cytotoxic but displays appreciable phototoxic, despite both complexes displaying very similar quantum yields for singlet oxygen sensitization. Optical microscopy suggests that the reason for these contrasting biological effects is that whereas the homoleptic complex localises in the nuclei of cells, the RuII (dppz)/ReI (dppn) complex preferentially accumulates in mitochondria. These observations illustrate how even small structural changes in metal based therapeutic leads can modulate their mechanism of action.

A Ruthenium(II) Polypyridyl Complex Disrupts Actin Cytoskeleton Assembly and Blocks Cytokinesis

The dinuclear Ru^II complex [(Ru(phen)₂)₂(tpphz)]⁴⁺ (phen=1,10‐phenanthroline, tpphz=tetrapyridophenazine) “RuRuPhen” blocks the transformation of G‐actin monomers to F‐actin filaments with no disassembly of pre‐formed F‐actin. Molecular docking studies indicate multiple RuRuPhen molecules bind to the surface of G‐actin but not the binding pockets of established actin polymerisation inhibitors. In cells, addition of RuRuPhen causes rapid disruption to actin stress fibre organisation, compromising actomyosin contractility and cell motility; due to this effect RuRuPhen interferes with late‐stage cytokinesis. Immunofluorescent microscopy reveals that RuRuPhen causes cytokinetic abscission failure by interfering with endosomal sorting complexes required for transport (ESCRT) complex recruitment.

A Ruthenium(II) Polypyridyl Complex Disrupts Actin Cytoskeleton Assembly and Blocks Cytokinesis

The dinuclear RuII complex [(Ru(phen)2)2(tpphz)]4+ (phen=1,10-phenanthroline, tpphz=tetrapyridophenazine) "RuRuPhen" blocks the transformation of G-actin monomers to F-actin filaments with no disassembly of pre-formed F-actin. Molecular docking studies indicate multiple RuRuPhen molecules bind to the surface of G-actin but not the binding pockets of established actin polymerisation inhibitors. In cells, addition of RuRuPhen causes rapid disruption to actin stress fibre organisation, compromising actomyosin contractility and cell motility; due to this effect RuRuPhen interferes with late-stage cytokinesis. Immunofluorescent microscopy reveals that RuRuPhen causes cytokinetic abscission failure by interfering with endosomal sorting complexes required for transport (ESCRT) complex recruitment.

Making the Right Link to Theranostics: The Photophysical and Biological Properties of Dinuclear RuII-ReI dppz Complexes Depend on Their Tether

The synthesis of 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 offer insights into these effects. While both complexes are live cells permeant, their intracellular localizations 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.

Using Nanoscopy To Probe the Biological Activity of Antimicrobial Leads That Display Potent Activity against Pathogenic, Multidrug Resistant, Gram-Negative Bacteria

Medicinal leads that are also compatible with imaging technologies are attractive, as they facilitate the development of therapeutics through direct mechanistic observations at the molecular level. In this context, the uptake and antimicrobial activities of several luminescent dinuclear Ru^II complexes against E. coli were assessed and compared to results obtained for another ESKAPE pathogen, the Gram-positive major opportunistic pathogen Enterococcus faecalis, V583. The most promising lead displays potent activity, particularly against the Gram-negative bacteria, and potency is retained in the uropathogenic multidrug resistant EC958 ST131 strain. Exploiting the inherent luminescent properties of this complex, super-resolution STED nanoscopy was used to image its initial localization at/in cellular membranes and its subsequent transfer to the cell poles. Membrane damage assays confirm that the complex disrupts the bacterial membrane structure before internalization. Mammalian cell culture and animal model studies indicate that the complex is not toxic to eukaryotes, even at concentrations that are several orders of magnitude higher than its minimum inhibitory concentration (MIC). Taken together, these results have identified a lead molecular architecture for hard-to-treat, multiresistant, Gram-negative bacteria, which displays activities that are already comparable to optimized natural product-based leads.

111In-labelled polymeric nanoparticles incorporating a ruthenium-based radiosensitizer for EGFR-targeted combination therapy in oesophageal cancer cells

Radiolabelled, drug-loaded nanoparticles may combine the theranostic properties of radionuclides, the controlled release of chemotherapy and cancer cell targeting. Here, we report the preparation of poly(lactic-co-glycolic acid) (PLGA) nanoparticles surface conjugated to DTPA-hEGF (DTPA = diethylenetriaminepentaacetic acid, hEGF = human epidermal growth factor) and encapsulating the ruthenium-based DNA replication inhibitor and radiosensitizer Ru(phen)2(tpphz)2+ (phen = 1,10-phenanthroline, tpphz = tetrapyridophenazine) Ru1. The functionalized PLGA surface incorporates the metal ion chelator DTPA for radiolabelling and the targeting ligand for EGF receptor (EGFR). Nanoparticles radiolabelled with 111In are taken up preferentially by EGFR-overexpressing oesophageal cancer cells, where they exhibit radiotoxicity through the generation of cellular DNA damage. Moreover, nanoparticle co-delivery of Ru1 alongside 111In results in decreased cell survival compared to single-agent formulations; an effect that occurs through DNA damage enhancement and an additive relationship between 111In and Ru1. Substantially decreased uptake and radiotoxicity of nanoparticles towards normal human fibroblasts and oesophageal cancer cells with normal EGFR levels is observed. This work demonstrates nanoparticle co-delivery of a therapeutic radionuclide plus a ruthenium-based radiosensitizer can achieve combinational and targeted therapeutic effects in cancer cells that overexpress EGFR.

A three-in-one-bullet for oesophageal cancer: replication fork collapse, spindle attachment failure and enhanced radiosensitivity generated by a ruthenium(ii) metallo-intercalator

Substitutionally inert ruthenium(ii) polypyridyl complexes have been developed as DNA intercalating agents yet cellular DNA damage responses to this binding modality are largely unexplored. Here, we show the nuclear-targeting complex [Ru(phen)2(tpphz)]2+ (phen = 1,10-phenanthroline, tpphz = tetrapyridophenazine) generates rapid and pronounced stalling of replication fork progression in p53-deficient human oesophageal cancer cells. In response, replication stress and double-strand break (DSB) DNA damage response (DDR) pathways are activated and cell proliferation is inhibited by growth arrest. Moreover, mitotic progression is compromised by [Ru(phen)2(tpphz)]2+, where the generation of metaphase chromosome spindle attachment failure results in spindle assembly checkpoint (SAC) activation. This dual mechanism of action results in preferential growth inhibition of rapidly-proliferating oesophageal cancer cells with elevated mitotic indices. In addition to these single-agent effects, [Ru(phen)2(tpphz)]2+ functions as a radiosensitizer with efficiency comparable to cisplatin, which occurs through a synergistic enhancement of DNA damage. These results establish that DNA replication is the target for [Ru(phen)2(tpphz)]2+ and provide the first experimental evidence that ruthenium-based intercalation targets multiple genome integrity pathways in cancer cells, thereby achieving enhanced selectivity compared to existing DNA-damaging agents such as cisplatin.

Body size, age and paternity in common brushtail possums (Trichosurus vulpecula)

Sexual selection should produce sexual size dimorphism in species where larger members of one sex obtain disproportionately more matings. Recent theory suggests that the degree of sexual size dimorphism depends on physical and temporal constraints involving the operational sex ratio, the potential reproductive rate and the trade-off between current reproductive effort and residual reproductive value. As part of a large-scale experiment on dispersal, we investigated the mating system of common brushtail possums inhabiting old-growth Eucalyptus forest in Australia. Paternity was assigned to 20 of 28 pouch-young (maternity known) genotyped at six microsatellite loci. Male mating success was strongly related to body size and age; male body weight and age being highly correlated. Despite disproportionate mating success favouring larger males, sexual size dimorphism was only apparent among older animals. Trapping and telemetry indicated that the operational sex ratio was effectively 1 : 1 and the potential reproductive rate of males was at most four times that of females. Being larger appeared to entail significant survival costs because males 'died-off' at the age at which sexual size dimorphism became apparent (8-9 years). Male and female home ranges were the same size and males appeared to be as sedentary as females. Moreover, longevity appears to be only slightly less important to male reproductive success than it is to females. It is suggested that a sedentary lifestyle and longevity are the key elements constraining selection for greater sexual size dimorphism in this 'model' medium-sized Australian marsupial herbivore.

Adjustment of offspring sex ratios in relation to the availability of resources for philopatric offspring in the common brushtail possum

The local-resource-competition hypothesis predicts that where philopatric offspring compete for resources with their mothers, offspring sex ratios will be biased in favour of the dispersing sex. This should produce variation in sex ratios between populations in relation to differences in the availability of resources for philopatric offspring. However, previous tests of local resource competition in mammals have used indirect measures of resource availability and have focused on sex-ratio variation between species or individuals rather than between local populations. Here, we show that the availability of den sites predicts the offspring sex ratio in populations of the common brushtail possum. Female possums defend access to dens, and daughters, but not sons, occupy dens within their mother's range. However, the abundances of possums in our study areas were determined principally by food availability. Consequently, in food-rich areas with a high population density, the per-capita availability of dens was low, and the cost of having a daughter should have been high. This cost was positively correlated with male bias in the sex ratio at birth. Low per capita availability of dens was correlated with male bias in the sex ratio at birth.

Diurnal and Nocturnal Grouping and Foraging Behaviors of Free-Ranging Eastern Grey Kangaroos

Group size, methods of surveillance and foraging rates of free-ranging eastern grey kangaroos, Macropus giganteus, were compared between night and day, from data on 24-h followings of 24 individuals. Kangaroos occurred in smaller groups in the dark but the reduction in group size took place before or around dusk, and could not be attributed to animals drifting apart after dark. Instead, changes in group size coincided with much movement by animals around dusk. Both males and females tended to spend less time surveying after dark, but females surveyed in fewer bouts at night than in the day. Females used the upright posture more at night than in the day; this is a conspicuous posture but one that probably enhanced their view of the surroundings. Foraging rates of kangaroos were lower after dark than before dusk because of an increased search time per bite. There was no evidence that other foraging parameters, such as rare of movement whilst feeding, were affected by darkness. Eastern grey kangaroos are one of the most social and diurnally active species of macropod and their highly flexible social system of open-membership groups appears to allow individuals to join and leave groups according to their foraging and safety requirements.

Ecology of the rufous hare-wallaby, Lagorchestes hirsutus Gould (Marsupialia : Macropodidae) in the Tanami Desert, Northern Territory.II Diet and feeding strategy

The diet preferences and selectivity of the rufous hare-wallaby in the Tanami Desert were examined at a number of sites and over a number of seasons by microscopic analysis of faecal pellets and direct observations. Perennial grasses were the most consistent plant items in the diet. Grass seeds were seasonally important as were the seeds and bulbs of sedges. Species of dicots were also used but most represented only minor components in the diet. Several species of plant common to the area were noticeably absent from the diet. Differences in the diets between four sites of varying floristic composition and fire history were consistent with differences in vegetation cover at each site. Overall, the absolute proportions and ratios of monocots and dicots and of leaf and seed portions were strongly similar for all sites, as were seasonal changes in the proportions of the four main plant categories (monocots, dicots, seeds and fruits). These changes correlated with local rainfall. Comparisons of plants eaten and plants available indicate the hare-wallabies' preference for monocots, particularly seed and fruit components. In contrast consumption of dicots was influericed by the declining quality of other preferred plants. Insects were seasonally important in the diet and appear to be a potentially important nitrogen supplement during drier times. The feeding strategy of the rufous hare-wallaby is flexible and enables it to exploit fully food resources whose availability is often limited in both time and space. During droughts it seems likely that the species is food stressed and this could lead to localised declines.

Macropod studies at Wallaby Creek. IX Exposure and responses of eastern grey kangaroos to dingoes

Kangaroos at Wallaby Creek lived with the persistent presence of dingoes in the valley, there being no place, time of year or of day when kangaroos could be free of risk. An adult kangaroo might encounter dingoes a few hundred times in its life. Dingoes appeared not to be selective for the sizes of groups of kangaroos that they contacted. Large adult males and females with medium pouch young were overrepresented in the samples of kangaroos contacted by dingoes. No kangaroos ignored the detected presence of dingoes; all became alert, and most fled. The distances at which they became alert to a dingo group depended upon the kangaroo group's size, larger groups never being surprised by dingoes at short range as were some smaller groups. On average larger groups fled when the dingoes were further away. Among classes of kangaroos, large adult males fled least far, and tended to react to dingoes less strongly (in terms of alertness or flight) than other classes. They also exhibited two forms of defence, taking to water when pursued and warding off attack, that other classes did not show.

Diets of Black-stripped wallabies in New South Wales

In both the wet and dry extremes of its remnant range in northern New South Wales, the black-striped wallaby, Macropus dorsalis, eats predominantly monocotyledonous plants, selecting leaves and, in some seasons, seedheads. The wallabies eat a wide range of monocot species, taking these from the habitat in which they shelter in the daytime as well as from that in which they forage at night. This study suggests that reserves for the conservation of the species need to include nocturnal foraging as well as diurnal sheltering habitats.

Macropod Studies at Wallaby Creek .8. Individual Recognition of Kangaroos and Wallabies

Recognition of individual large mammals by natural features is an ancient practice, the usefulness of which has recently become appreciated in field studies. We show that such recognition is possible and repeatable, under particular circumstances, with macropodid marsupials in the field in Australia. In trials, there was a 98% agreement between observers in identification of individuals of both eastern grey kangaroos Macropus giganteus and red-necked wallabies M. rufogriseus. Characters used to identify individuals were first definitive ('oddity') characters, and then specific sets of character-states. However, in time observers came to recognise individuals 'on sight', by unconscious summation of character-states. Recognition skills could be readily learned by observers, allowing almost complete populations of these species to be known and the component members studied individually. The technique should be applicable in studies of other macropodid populations.

Macropod Studies at Wallaby Creek .1. The Area and Animals

This paper introduces a series of papers on the ecology, social organisation and behaviour of populations of sympatric macropods (Macropodoidea : Marsupialia) in north-eastern New South Wales. The study site, in the valley of Wallaby Creek, covers partly tree-cleared cattle-grazed pastures and also wet and dry forest communities; 10 species of macropods live there. The valley has a moderately high rainfall (1023 mm per annum), falling predominately in summer, and an equable climate of cool winters and warm summers. Soils derived from sedimentary and basaltic rocks and alluvium support naturally diverse plant associations further diversified by clearing and establishment of pasture and weed species. Macropods favouring open country occupy the pastures, which can also be used by cover-dependent species where pasture abuts forest or remnant patches of cover. Composition of the macropod community has changed since development of the pasture zone. Dingoes, major predators of some of the macropods, are abundant, and all exotic mammals other than cattle are rare. Populations of two of the macropod species are habituated to approach by observers, and close observation, on foot, of undisturbed animals has become our common study technique. A 1-ha grid has been established over 3.7 km2 of the study site to facilitate exact location of animals and observations. The suitability of the macropod populations for this kind of study results from the attitudes of the landholders.

Ranging of Eastern Grey Kangaroos and Wallaroos on a New England Pastoral Property

Eastern grey kangaroos and wallaroos were caught, collared or radio-collared, and released on part of a developed New England pastoral property, to investigate dispersal from and within the property. A few grey kangaroos, but no wallaroos, were detected dispersing relatively long distances (up to 17 km). Most individuals of both species were sedentary in small, overlapping home ranges.