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  • Journal article
    Zhang G, Lin S, Leow CH, Pang KT, Hernandez Gil J, Long N, Eckersley R, Matsunaga T, Tang Met al., 2019,

    Quantification of vaporized targeted nanodroplets using high-frame-rate ultrasound and optics

    , Ultrasound in Medicine and Biology, Vol: 45, Pages: 1131-1142, ISSN: 0301-5629

    Owing to their ability to efficiently deliver biological cargo and sense the intracellular milieu, vertical arrays of high aspect ratio nanostructures, known as nanoneedles,are being developed as minimally invasive tools for cell manipulation. However, little is known of the mechanisms of cargo transfer across the cell membrane-nanoneedle interface. Particularly,the contributions of membrane piercing, modulation of membrane permeability and endocytosis to cargo transfer remain largelyunexplored. Here, combining state-of-the-art electron and scanning ion conductance microscopy with molecular biology techniques, we show that porous silicon nanoneedle arrays concurrently stimulate independent endocytic pathways which contribute to enhanced biomolecule delivery into human mesenchymal stem cells. Electron microscopy of the cell membrane at nanoneedle sites shows an intact lipid bilayer, accompanied by an accumulation of clathrin-coated pits and caveolae. Nanoneedles enhance the internalisation of biomolecular markers of endocytosis, highlighting the concurrent activation of caveolae-and clathrin-mediated endocytosis, alongside macropinocytosis. These events contribute to the nanoneedle-mediated delivery (nanoinjection) of nucleic acids into human stem cells, which distribute across the cytosol and the endolysosomal system. This data extends the understanding of how nanoneedles modulate biological processes to mediate interaction with the intracellular space, providing indications for the rational design of improved cell-manipulation technologies.

  • Conference paper
    Cooper S, Yue T, Miller P, Ma M, Long Net al., 2019,

    Tripodal N-centred phosphine ligands: Towards a novel donor set for <SUP>99m</SUP>Tc and <SUP>186/188</SUP>Re radiopharmaceutical formulation

    , Publisher: WILEY, Pages: S295-S296, ISSN: 0362-4803
  • Journal article
    Pensa E, Karpowicz R, Jabaoński A, Trzybiński D, Woźniak K, Šakić D, Vrček V, Long NJ, Albrecht T, Kowalski Ket al., 2019,

    Gold-Induced Desulfurization in a Bis(ferrocenyl) Alkane Dithiol

    , Organometallics, ISSN: 0276-7333

    © 2019 American Chemical Society. Thiol-modified ferrocenes on gold have been archetypical model systems for many fundamental charge transfer and other studies, since both thiol-gold and ferrocene redox chemistry are considered to be well-understood. Thus unexpectedly, we found that for a representative of a new class of flexibly linked bis-ferrocenyl compounds, namely, 1-10-bis(1-ferrocenyl)decane dithiol, surface immobilization on gold failed. Instead, in the presence of gold, molecular decomposition took place, resulting in sulfur-based adlayers and well-defined molecular elimination products, for which we provide spectroscopic evidence. Careful control experiments and comparison with related ferrocene compounds provide insight into the mechanism of the observed elimination reactions, as a combined effect of the molecular structure and the nature of the gold/sulfur bond. These findings, thus, have a broader impact on the design of molecular adlayers, for example, in the context of surface functionalization in sensing or the synthesis of gold nanoparticles.

  • Conference paper
    Leber R, Wilson L, Robaschik P, Inkpen M, Payne D, Long N, Albrecht T, Hirjibehedin C, Heutz Set al., 2019,

    Vacuum deposition of biferrocene thin films: growth strategies for stability and tuneable magnetism

    , 257th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
  • Journal article
    Clough TJ, Jiang L, Wong K-L, Long NJet al., 2019,

    Ligand design strategies to increase stability of gadolinium-based magnetic resonance imaging contrast agents

    , NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723
  • Conference paper
    Leow CH, Braga M, Bush NL, Stanziola A, Shah A, Hernández-Gil J, Long NJ, Aboagye EO, Bamber JC, Tang MXet al., 2019,

    Contrast vs non-contrast enhanced microvascular imaging using acoustic sub-aperture processing (ASAP): in vivo demonstration

    , IEEE International Ultrasonics Symposium, IUS. 2018, Publisher: IEEE, ISSN: 1948-5719

    Angiogenesis plays a vital role in the progression of cancer. Non-invasive imaging techniques capable of assessing the microenvironment are therefore of clinical interest. Although highly sensitive vascular mapping has been demonstrated using ultrafast Power Doppler (PD), the detectability of microvasculature from the background noise may be hindered by the low signal-to-noise ratio (SNR) in deeper region and without the use of contrast agents. We recently developed acoustic sub-aperture processing (ASAP) processing for super-contrast vasculature imaging. This technique relies on the spatial coherence of the backscattered echoes over different acquisitions to substantially reduce the noise floor compared to the power Doppler (PD) technique. In this study, we demonstrate the feasibility of applying ASAP processing for non-contrast enhanced microvascular imaging in preclinical condition, and compare it with contrast enhanced ASAP as well as ultrafast PD. Comparing to PD, ASAP exhibit SNR improvement up to 12 dB. Higher SNR and extra visibility of smaller vessel are also demonstrated in contrast enhanced images in comparison to the non-contrast images. In conclusion, we have demonstrated the feasibility of using ASAP in vivo for non-contrast microvascular imaging, and the added benefit of using contrast agents in microvascular imaging.

  • Conference paper
    Hau Leow C, Bush NL, Stanziola A, Braga M, Shah A, Hemández-Gil J, Long NJ, Aboagye EO, Bamber JC, Tang MXet al., 2019,

    High-contrast 3D in vivo microvascular imaging using scanning 2D ultrasound and acoutic sub-aperture processing (ASAP)

    , IEEE International Ultrasonics Symposium, IUS. 2018, Publisher: IEEE, ISSN: 1948-5719

    Non-invasive techniques for microvascular environment assessment are invaluable for clinical diagnosis and treatment monitoring. We recently developed a super contrast processing to suppress noise background in ultrafast Power Doppler, known an acoustic sub-aperture processing (ASAP), and demonstrate using 2D contrast enhance ultrasound. However, 2D imaging is insufficient to represent the 3D complex vascular environment. We therefore extend our study to demonstrate the feasibility of our technique for volumetric imaging. A pseudo-3D imaging technique was developed and demonstrated using a research system and preclinical transducer. A mouse liver was scanned using 2D ultrafast ultrasound and a mechanical translation stage. Initial results not only demonstrated a substantial noise reduction in 2D vascular images using ASAP, but also a high contrast volumetric rendering of a mouse liver. Our technique is ready for clinical use to provide better evaluation of angiogenesis.

  • Journal article
    Jantan KA, McArdle J, Mognon L, Fiorini V, Wilkinson LA, White AJP, Stagni S, Long NJ, Wilton-Ely Jet al., 2019,

    Heteromultimetallic compounds based on polyfunctional carboxylate linkers

    , New Journal of Chemistry, Vol: 43, Pages: 3199-3207, ISSN: 1144-0546

    A series of homo- and hetero-nuclear, bi- and trimetallic compounds are accessible using polyfunctional linkers with carboxylic acid and alkynyl or pyridyl donor combinations. This versatile approach affords reaction at a specific donor site in each case, to accommodate both ruthenium(II) or osmium(II) units and also rhenium and gold centres. Due to the orientation of the nitrogen donors of the bipyridyl moiety in 2,2′-bipyridine-4,4′-dicarboxylic acid, the metal addition must be performed in a certain sequence due to steric considerations. One example was investigated crystallographically to add to the spectroscopic and analytical characterisation performed for all complexes. Photophysical investigations reveal the effect of incorporating second or third row transition metal centres. This approach was expanded through the use of a linker bearing both carboxylic acid and alkynyl functionalities, 1,1′-ethynylferrocene carboxylic acid. This allows initial coordination of the carboxylate donors to be followed by the formation of either an acetylide or a vinyl bridge to another metal, providing access to heterotrimetallic (FeRuOs and FeRuAu) compounds as well as a heteroheptametallic Fe3Ru2Au2 example. Preliminary electrochemical studies were performed on the latter compound.

  • Journal article
    Mann PB, McGregor IJ, Bourke S, Burkitt-Gray M, Fairclough S, Ma MT, Hogarth G, Thanou M, Long N, Green Met al., 2019,

    An atom efficient, single-source precursor route to plasmonic CuS nanocrystals

    , NANOSCALE ADVANCES, Vol: 1, Pages: 522-526, ISSN: 2516-0230
  • Journal article
    Rains JGD, ODonnelly K, Oliver T, Woscholski R, Long NJ, Barter LMCet al., 2019,

    Bicarbonate inhibition of carbonic anhydrase mimics hinders catalytic efficiency: Elucidating the mechanism and gaining insight toward improving speed and efficiency

    , ACS Catalysis, Vol: 9, Pages: 1353-1365, ISSN: 2155-5435

    Carbonic anhydrase (CA) mimics are often studied with a focus on the hydration of CO2 for atmospheric carbon capture. Consequently, the reverse reaction (dehydration of HCO3–) has received minimal attention, so much so that the rate-limiting step of the dehydration reaction in CA mimics is currently unknown. The rate-limiting step of the hydration reaction is reported to be the bicarbonate-bound intermediate step, and thus is susceptible to product inhibition. It is not, however, clear if this inhibition is a consequence of an increase in the rate of the competing dehydration reaction or resulting from the strong affinity of bicarbonate to the mimic. To address this, insight into the dehydration reaction kinetics is needed. We therefore report the most comprehensive study of a CA mimic to date. The dehydration profile of the fastest small-molecule CA mimic, ZnL1S, was characterized, and consequently evidence for the rate-limiting step for the dehydration reaction was seen to be the bicarbonate-bound intermediate step, much like the hydration reaction. This experimental validation of the rate-limiting step was achieved through a variety of methods including NMR experiments and the effect of inhibitors, substrate concentration, and metal center on activity. With this understanding, an improvement in the favorability of the rate-limiting step was achieved, resulting in decreased bicarbonate inhibition. Thus, an increase in the mimic’s kcat for both reactions was observed, resulting in the largest rate constants of any small-molecule CA mimic reported to date (28 093 and 579 M–1 s–1 for hydration and dehydration, respectively). Enzyme-like kcat/km values were obtained for ZnL1S (5.9 × 105 M–1 s–1 for CO2 hydration), and notably there is only a difference of 2.5 orders of magnitude from the enzyme, the closest of any CA mimic reported in the literature. The results from this work can be applied to the development and improvement

  • Journal article
    Wilkinson L, Massey E, Yue T, White A, Long Net al., 2019,

    Cyanoferrocenes as redox-active metalloligands for coordination-driven self-assembly

    , Dalton Transactions, Vol: 48, Pages: 72-78, ISSN: 1477-9234

    Ferrocene-based Lewis bases have found utility as metalloligands in a wide variety of applications. The coordination chemistry of cyanoferrocenes however, is underexplored. Herein, we describe a new synthetic protocol for the generation of cyanoferrocenes. The coordination chemistry of these metalloligands to [Cu(NCMe)4][PF6], [(PPh3)2Cu(NCMe)2][PF6] and [(dppf)Cu(NCMe)2][PF6] salts has been explored, providing crystallographic evidence of cluster and polymeric forms of 1,1′- and 1,2-dicyanoferrocene complexes. The stability of the complexes and ligand dissociation were found to be strongly solvent-dependent.

  • Conference paper
    Zhang G, Harput S, Shah A, Hernandez-Gil J, Zhu J, Christensen-Jeffries K, Brown J, Long NJ, Eckersley RJ, Dunsby C, Bamber J, Tang M-Xet al., 2019,

    Photoacoustic Super-Resolution Imaging using Laser Activation of Low-Boiling-Point Dye-Coated Nanodroplets in vitro and in vivo

    , IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 944-947, ISSN: 1948-5719
  • Conference paper
    Lahri R, Rahman M, Hernandez-Gil J, Long N, Kosmas P, Thanou Met al., 2019,

    Examination of zinc ferrites vs. iron oxides as contrast agents for microwave systems

    , 13th European Conference on Antennas and Propagation (EuCAP), Publisher: IEEE, ISSN: 2164-3342
  • Journal article
    Smith A, Blower P, Southworth R, Ma M, Long Net al., 2018,

    Synthesis, gallium-68 radiolabelling and biological evaluation of a series of triarylphosphonium-functionalized DO3A chelators

    , Dalton Transactions, Vol: 47, Pages: 15448-15457, ISSN: 1477-9234

    Radiolabelled lipophilic cations that accumulate in mitochondria according to the magnitude of the mitochondrial membrane potential can be used to report non-invasively on mitochondrial dysfunction in cardiovascular disease, cardiotoxicity, and cancer. While several such cations are already commercially available for SPECT imaging, PET offers greater promise in terms of sensitivity, resolution, and capacity for dynamic imaging and pharmacokinetic modelling. We have therefore synthesised a series of three triarylphosphonium-functionalised DO3A chelators for positron emitter gallium-68, with differing alkyl-functionalisation motifs to provide opportunities for tunable lipophilicity as a means of optimising their pharmacokinetics. To assess their capacity to report on mitochondrial membrane potential, we assessed their pharmacokinetic profiles in isolated tumour cells and isolated perfused rat hearts before and after mitochondrial depolarisation with the ionophore CCCP. All three compounds radiolabelled with over 97% RCY and exhibited log D values of between −3.12 and −1.81. In vitro assessment of the uptake of the radiotracers in cultured tumour cells showed a three-fold increase in uptake compared to unchelated [68Ga]Ga(III). However, each complex exhibited less than 1% retention in healthy hearts, which was not significantly diminished by mitochondrial depolarisation with CCCP. This preliminary work suggests that while this approach is promising, the lipophilicity of this class of tracers must be increased in order for them to be useful as cardiac or cancer imaging agents.

  • Journal article
    Li B, Famili M, Pensa E, Grace I, Long NJ, Lambert C, Albrecht T, Cohen LFet al., 2018,

    Cross-plane conductance through a graphene/molecular monolayer/Au sandwich

    , Nanoscale, Vol: 10, Pages: 19791-19798, ISSN: 2040-3364

    The functionalities offered by single-molecule electrical junctions are yet to be translated into monolayer or few-layer molecular films, where making effective and reproducible electrical contact is one of the challenging bottlenecks. Here we take a significant step in this direction by demonstrating that excellent electrical contact can be made with a monolayer biphenyl-4,4′-dithiol (BPDT) molecular film, sandwiched between gold and graphene electrodes. This sandwich device structure is advantageous, because the current flows through the molecules to the gold substrate in a ‘cross-plane’ manner, perpendicular to the plane of graphene, yielding high-conductance devices. We elucidate the nature of the cross-plane graphene/molecule/Au transport using quantum transport calculations and introduce a simple analytical model, which captures generic features of the current–voltage characteristic. Asymmetry in junction properties results from the disparity in electrode electrical properties, the alignment of the BPDT HOMO–LUMO energy levels and the specific characteristics of the graphene electrode. The experimental observation of scalability of junction properties within the junction area, in combination with a theoretical description of the transmission probability of the thiol–graphene contact, demonstrates that between 10% and 100% of the molecules make contact with the electrodes, which is several orders of magnitude greater than that achieved to date in the literature.

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