Ecological habitat partitioning and feeding specialisations of coastal minke whales (Balaenoptera acutorostrata) using a recently designated MPA in northeast Scotland.

In the design of protected areas for cetaceans, spatial maps rarely take account of the life-history and behaviour of protected species relevant to their spatial ambit, which may be important for their management. In this study, we examined the distribution and feeding behaviours of adult versus juvenile minke whales (Balaenoptera acutorostrata) from long-term studies in the Moray Firth in northeast Scotland, where a Marine Protected Area (MPA) has recently been designated. Data were collected during dedicated boat surveys between 2001 and 2022 inclusive, from which 784 encounters with 964 whales of confirmed age-class (471 juveniles and 493 adults) were recorded from 56,263 km of survey effort, resulting in 238 focal follows. Adults and juveniles were occasionally seen together, but their distributions were not statistically correlated, and GIS revealed spatial separation / habitat partitioning by age-class-with juveniles preferring shallower, inshore waters with sandy-gravel sediments, and adults preferring deeper, offshore waters with greater bathymetric slope. GAMs suggested that the partitioning between age-classes was predominantly based on the differing proximity of animals to the shore, with juveniles showing a preference for the gentlest seabed slopes, and both adults and juveniles showing a similar preference for sandy gravel sediment types. However, the GAMs only used sightings data with available survey effort (2008 to 2022) and excluded depth due to collinearity issues. Whilst adult minkes employed a range of "active" prey-entrapment specialisations, showing inter-individual variation and seasonal plasticity in their targeted prey, juveniles almost exclusively used "passive" (low energy) feeding methods targeting low-density patches of inshore prey. These findings corroborate the need to incorporate demographic and behavioural data into spatial models when identifying priority areas for protected cetacean species. Not all areas within an MPA have equal value for a population and a better knowledge of the spatial preferences of these whales within the designated Scottish MPAs, appointed for their protection, is considered vital for their conservation.

Ru(ii)/BODIPY core co-encapsulated ratiometric nanotools for intracellular O2 sensing in live cancer cells.

Oxygen is a crucial reagent in many biochemical processes within living cells and its concentration can be an effective marker in disease, particularly in cancer where tissue hypoxia has been shown to indicate tumour growth. Probes that can reflect the oxygen concentration and distribution using ratiometric signals can be applied to a range of conventional methods without the need for specialised equipment and are particularly useful. The preparation and in cellulo study of luminescent ratiometric core-shell nanoparticles are presented. Here, a new lipophilic and oxygen-responsive Ru(ii) tris-heteroleptic polypyridyl complex is co-encapsulated with a reference BODIPY dye into the core of poly-l-lysine-coated polystyrene particles. The co-core encapsulation ensures oxygen response but reduces the impact of the environment on both probes. Single wavelength excitation of the particles, suspended in aqueous buffer, at 480 nm, triggers well-resolved dual emission from both dyes with peak maxima at 515 nm and 618 nm. A robust ratiometric oxygen response is observed from water, with a linear dynamic range of 3.6-262 µM which matches well with typical biological ranges. The uptake of RuBDP NPs was found to be cell-line dependent, but in cancerous cell lines, the particles were strongly permeable with late endosomal and partial lysosomal co-staining observed within 3 to 4 hours, eventually leading to extensive staining of the cytoplasm. The co-localisation of the ruthenium and BODIPY emission confirms that the particles remain intact in cellulo with no indication of dye leaching. The ratiometric O2 sensing response of the particles in cellulo was demonstrated using a plate-based assay and by confocal xyλ scanning of cells exposed to hypoxic conditions.

Solvent switchable dual emission from a bichromophoric ruthenium-BODIPY complex.

A ruthenium(II) polypyridyl-BODIPY dyad is presented which exhibits a solvent switchable dual emission. Intense oxygen sensitive emission from the ruthenium centre and O2 independent emission from the BODIPY centre, are both observed in organic media. In aqueous media, the BODIPY emission is reversibly switched off leaving only a ruthenium centred emission. The materials are interesting both as self-referenced O2 probes and for cell/tissue imaging.

Osmium(II) polypyridyl polyarginine conjugate as a probe for live cell imaging; a comparison of uptake, localization and cytotoxicity with its ruthenium(II) analogue.

A first investigation into the application of a luminescent osmium(ii) bipyridine complex to live cell imaging is presented. Osmium(ii) (bis-2,2-bipyridyl)-2(4-carboxylphenyl) imidazo[4,5f][1,10]phenanthroline was prepared and conjugated to octaarginine, a cell penetrating peptide. The photophysics, cell uptake and cytotoxicity of this osmium complex conjugate were performed and compared with its ruthenium analogue. Cell uptake and distribution of both ruthenium and osmium conjugates were very similar with rapid transmembrane transport of the osmium probe (complete within approx. 20 min) and dispersion throughout the cytoplasm and organelles. The near-infrared (NIR) emission of the osmium complex (λmax 726 nm) coincides well with the biological optical window and this facilitated luminescent and luminescence lifetime imaging of the cell which was well resolved from cell autofluorescence. The large Stokes shift of the emission also permitted resonance Raman mapping of the dye within CHO cells. Rather surprisingly, the osmium conjugate exhibited very low cytotoxicity when incubated both in the dark and under visible irradiation. This was attributed to the remarkable stability of this complex which was reflected by the complete absence of photo-bleaching of the complex even under extended continuous irradiation. In addition, when compared to its ruthenium analogue its luminescence was short-lived in water therefore rendering it insensitive to O2.

Electrodeposited gold-copper core-shell nanowires for high sensitivity DNA detection.

Gold-Copper core shell nanowires have been electrodeposited and their electrochemical and Raman properties probed. First, hollow copper nanotubes, 3.2 ± 0.1 µm long, with a uniform diameter of 70 ± 22 nm, were electrodeposited within the pores of a track etched polycarbonate membrane filter. Second, gold was then electrodeposited within these copper cylinders to yield the gold-copper core-shell nanowires. Nanowires, functionalised with probe strand DNA, that is complementary to that of the pathogen Staph. Aureus, only on their ends, can be immobilised onto an electrode surface in a DNA sandwich assay. Significantly, the charge associated with the selective oxidation of the copper shell depends linearly on the target DNA concentration from 1 nM to 100 µM.

RGD labeled Ru(II) polypyridyl conjugates for platelet integrin αIIbß3 recognition and as reporters of integrin conformation.

The ability of two novel ruthenium(II) polypyridyl-Arg-Gly-Asp (RGD) peptide conjugates to act as molecular probes for reporting on the presence and conformation of integrin αIIbß3 in solution and in live cells was described. The compounds are [Ru(bpy)2PIC-RGD](2+), bpy-RGD, and [Ru(dpp)2PIC-RGD](2+), dpp-RGD, where dpp is 4,7-diphenyl-1,10-phenanthroline, bpy is 2,2'-bipyridine, and PIC is 2-(4-carboxyphenyl)imidazo[4,5-f][1,10]phenanthroline. Bpy-RGD is hydrophilic, whereas dpp-RGD is comparatively hydrophobic. Both probes exhibited good affinity and high specificity for purified αIIbß3 in solution. Binding of either complex to the resting integrin resulted in an approximately 8-fold increase of emission intensity from the metal center with dissociation constants (Kd) in the micromolar range for each complex. The Kd for each conjugate/αIIbß3 assembly were compared following treatment of the integrin with the activating agents, Mn(2+) and dithiothreitol (DTT), which are commonly used to induce active-like conformational changes in the integrin. For bpy-RGD/αIIbß3 Kd showed relatively little variation with integrin activation, presenting the following trend: denatured αIIbß3 > resting αIIbß3 = pretreated DTT = pretreated Mn(2+). Kd for dpp-RGD/ αIIbß3 showed greater variation with integrin activation and the following trend was followed: denatured αIIbß3 > resting αIIbß3 > pretreated Mn(2+) = pretreated DTT. Time resolved luminescence anisotropy was carried out to obtain the rotational correlation time of bpy-RGD and dpp-RGD bound to resting or nominally activated integrin. The rotational correlation times of bpy-RGD and dpp-RGD, too fast to measure unbound, decreased to 1.50 ± 0.03 µs and 2.58 ± 0.04 µs, respectively, when the complexes were bound to resting integrin. Addition of Mn(2+) to bpy-RGD/αIIbß3 or dpp-RGD/αIIbß3 reduced the rotational correlation time of the ruthenium center to 1.29 ± 0.03 µs and to 1.72 ± 0.03 µs, respectively. Following treatment, the rotational correlation time decreased to 1.04 ± 0.01 µs and 1.29 ± 0.03 µs for bpy-RGD/αIIbß3, and dpp-RGD/αIIbß3, respectively. The large relative changes in rotational correlation times observed for Mn(2+) or DTT activated integrin indicates significant change in protein conformation compared with the resting integrin. The results also indicated that the metal complex itself affects the final conformational and/or aggregation status of the protein obtained. Furthermore, the extent of conformational change was influenced by whether the probe was bound to the integrin before or after activator treatment. Finally, in vitro studies indicated that both probes selectively bind to CHO cells expressing the resting form of αIIbß3. In each case the probe colocalized with αIIb specific SZ22 antibody. Overall, this work indicates that bpy-RGD and dpp-RGD may be useful peptide-probes for rapid assessment of integrin structural status and localization in solution and cells.

Peptide directed transmembrane transport and nuclear localization of Ru(II) polypyridyl complexes in mammalian cells.

The targeted delivery of luminescent Ru(II) polypyridyl complexes to the nucleus of live mammalian cells by a Nuclear Localisation Signal (NLS) peptide; NF-κB is demonstrated.

Cell uptake and cytotoxicity of a novel cyclometalated iridium(III) complex and its octaarginine peptide conjugate.

The synthesis and characterisation of iridium(III) bis(2-(2,4-difluorophenyl)pyridinato-N, C2')-2(4-carboxylphenyl)imidazo[4,5-f][1,10]phenanthroline perchlorate, [Ir(dfpp)(2)(picCOOH)](+) and its octaarginine conjugate [Ir(dfpp)(2)(picCONH-Arg(8))](9+) are reported. Both complex and conjugate exhibit intense and long-lived luminescence, which is O(2) and pH sensitive. Conjugation to the polyarginine peptide renders the complex very water soluble. The uptake of the parent iridium(III) complex and conjugate are compared in two mammalian cell lines; SP2 myeloma and Chinese hamster ovary (CHO). Both complexes internalise into the cytoplasm, however dye uptake rate and distribution vary with peptide conjugation and with cell identity. Whereas transmembrane transport is thought to have been facilitated by the dimethyl sulfoxide (DMSO) used as co-solvent (0.05% v/v) for the parent complex, the octaarginine, the dye-conjugate (iridium-R(8)) is membrane permeable in water only. Both complexes exhibit high cytotoxicity, evident through blebbing and vacuole formation within living cells, indicative of apoptosis, within 30min of exposure to the probe. The IC(50) recorded for the cells in the dark was independent, in the case of the parent complex, of the identity of the cell, with IC(50) of 84.8µM and 88µM respectively for SP2 and CHO cells. The IC(50) approximately doubled for the polyarginine conjugate and displayed a significant dependence on cell type with IC(50) of 35µM and 54.1µM respectively for SP2 and CHO cells. These IC(50) values were recorded in the dark. However under irradiation cell death is considerably faster. Evidence from imaging suggests that the conjugate penetrates the nucleus whereas the parent does not, indicating that nuclear penetration may play a role in cytotoxicity.