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  • Journal article
    Baker CA, Romain C, Long NJ, 2021,

    Cation-π interactions enabling hard/soft Ti/Ag heterobimetallic cooperativity in lactide ring-opening polymerisation

    , CHEMICAL COMMUNICATIONS, Vol: 57, Pages: 12524-12527, ISSN: 1359-7345
  • Journal article
    Braga M, Leow CH, Gil JH, Teh JH, Carroll L, Long NJ, Tang M-X, Aboagye EOet al., 2021,

    Investigating CXCR4 expression of tumor cells and the vascular compartment: A multimodal approach

    , PLoS One, Vol: 16, Pages: 1-21, ISSN: 1932-6203

    The C-X-C chemokine receptor 4 (CXCR4) is G protein-coupled receptor that upon binding to its cognate ligand, can lead to tumor progression. Several CXCR4-targeted therapies are currently under investigation, and with it comes the need for imaging agents capable of accurate depiction of CXCR4 for therapeutic stratification and monitoring. PET agents enjoy the most success, but more cost-effective and radiation-free approaches such as ultrasound (US) imaging could represent an attractive alternative. In this work, we developed a targeted microbubble (MB) for imaging of vascular CXCR4 expression in cancer. A CXCR4-targeted MB was developed through incorporation of the T140 peptide into the MB shell. Binding properties of the T140-MB and control, non-targeted MB (NT-MB) were evaluated in MDA-MB-231 cells where CXCR4 expression was knocked-down (via shRNA) through optical imaging, and in the lymphoma tumor models U2932 and SuDHL8 (high and low CXCR4 expression, respectively) by US imaging. PET imaging of [18F]MCFB, a tumor-penetrating CXCR4-targeted small molecule, was used to provide whole-tumor CXCR4 readouts. CXCR4 expression and microvessel density were performed by immunohistochemistry analysis and western blot. T140-MB were formed with similar properties to NT-MB and accumulated sensitively and specifically in cells according to their CXCR4 expression. In NOD SCID mice, T140-MB persisted longer in tumors than NT-MB, indicative of target interaction, but showed no difference between U2932 and SuDHL8. In contrast, PET imaging with [18F]MCFB showed a marked difference in tumor uptake at 40–60 min post-injection between the two tumor models (p<0.05). Ex vivo analysis revealed that the large differences in CXCR4 expression between the two models are not reflected in the vascular compartment, where the MB are restricted; in fact, microvessel density and CXCR4 expression in the vasculature was comparable between U2932 and SuDHL8 tumors. In conclusion, we success
  • Journal article
    Osborne BE, Yue TTC, Waters ECT, Baark F, Southworth R, Long NJet al., 2021,

    Synthesis and <i>ex vivo</i> biological evaluation of gallium-68 labelled NODAGA chelates assessing cardiac uptake and retention

    , DALTON TRANSACTIONS, Vol: 50, Pages: 14695-14705, ISSN: 1477-9226
  • Journal article
    Teh JH, Braga M, Allott L, Barnes C, Hernandez-Gil J, Tang M-X, Aboagye EO, Long NJet al., 2021,

    A kit-based aluminium-[F-18]fluoride approach to radiolabelled microbubbles

    , Chemical Communications, Vol: 57, Pages: 11677-11680, ISSN: 1359-7345

    The production of 18F-labelled microbubbles (MBs) via the aluminium-[18F]fluoride ([18F]AlF) radiolabelling method and facile inverse-electron-demand Diels–Alder (IEDDA) ‘click’ chemistry is reported. An [18F]AlF-NODA-labelled tetrazine was synthesised in excellent radiochemical yield (>95% RCY) and efficiently conjugated to a trans-cyclooctene (TCO) functionalised phospholipid (40–50% RCY), which was incorporated into MBs (40–50% RCY). To demonstrate the potential of producing 18F-labelled MBs for clinical studies, we also describe a kit-based approach which is amenable for use in a hospital radiopharmacy setting.
  • Journal article
    Walter ERH, Cooper SM, Boyle JJ, Long NJet al., 2021,

    Enzyme-activated probes in optical imaging: a focus on atherosclerosis

    , DALTON TRANSACTIONS, Vol: 50, Pages: 14486-14497, ISSN: 1477-9226
  • Journal article
    Wu Y, Chau H, Thor W, Chan KHY, Ma X, Chan W, Long NJ, Wong Ket al., 2021,

    Solid‐Phase Peptide Macrocyclization and Multifunctionalization via Dipyrrin Construction

    , Angewandte Chemie, Vol: 133, Pages: 20463-20469, ISSN: 0044-8249

    <jats:title>Abstract</jats:title><jats:p>We introduce a new and highly efficient synthetic protocol towards multifunctional fluorescent cyclopeptides by solid‐phase peptide macrocyclization via dipyrrin construction, with full scope of proteinogenic amino acids and different ring sizes. Various bicyclic peptides can be created by dipyrrin‐based crosslinking and double dipyrrin‐ring formation. The embedded dipyrrin can be either transformed to fluorescent BODIPY and then utilized as cancer‐selective targeted protein imaging probe in vitro, or directly employed as a selective metal sensor in aqueous media. This work provides a valuable addition to the peptide macrocyclization toolbox, and a blueprint for the development of multifunctional dipyrrin linkers in cyclopeptides for a wide range of potential bioapplications.</jats:p>
  • Journal article
    Wu Y, Chau H-F, Thor W, Chan KHY, Ma X, Chan W-L, Long NJ, Wong K-Let al., 2021,

    Solid-Phase Peptide Macrocyclization and Multifunctionalization via Dipyrrin Construction

    , ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 60, Pages: 20301-20307, ISSN: 1433-7851
  • Journal article
    Jiang L, Mak H-N, Walter ERH, Wong W-T, Wong K-L, Long NJet al., 2021,

    A fluorescent probe for the discrimination of oxidation states of palladium

    , CHEMICAL SCIENCE, Vol: 12, Pages: 9977-9982, ISSN: 2041-6520
  • Journal article
    Chau H-F, Wu Y, Fok W-Y, Thor W, Cho WC-S, Ma P, Lin J, Mak N-K, Bunzli J-CG, Jiang L, Long NJ, Lung HL, Wong K-Let al., 2021,

    Lanthanide-Based Peptide-Directed Visible/Near-Infrared Imaging and Inhibition of LMP1

    , JACS AU, Vol: 1, Pages: 1034-1043
  • Journal article
    Farleigh M, Pham TT, Yu Z, Kim J, Sunassee K, Firth G, Forte N, Chudasama V, Baker JR, Long NJ, Rivas C, Ma MTet al., 2021,

    New Bifunctional Chelators Incorporating Dibromomaleimide Groups for Radiolabeling of Antibodies with Positron Emission Tomography Imaging Radioisotopes

    , BIOCONJUGATE CHEMISTRY, Vol: 32, Pages: 1214-1222, ISSN: 1043-1802
  • Journal article
    Boltersdorf T, Gavins FNE, Long NJ, 2021,

    Long-lived lanthanide emission <i>via</i> a pH-sensitive and switchable LRET complex

    , CHEMICAL SCIENCE, ISSN: 2041-6520
  • Journal article
    Walter E, Ge Y, Mason J, Boyle J, Long Net al., 2021,

    A coumarin-porphyrin FRET break-apart probe for heme oxygenase-1

    , Journal of the American Chemical Society, Vol: 143, Pages: 6460-6469, ISSN: 0002-7863

    Heme oxygenase-1 (HO-1) is a vital enzyme in humans that primarily regulates free heme concentrations. The overexpression of HO-1 is commonly associated with cardiovascular and neurodegenerative diseases including atherosclerosis and ischemic stroke. Currently, there are no known chemical probes to detect HO-1 activity, limiting its potential as an early diagnostic/prognostic marker in these serious diseases. Reported here are the design, synthesis, and photophysical and biological characterization of a coumarin–porphyrin FRET break-apart probe to detect HO-1 activity, Fe–L1. We designed Fe–L1 to “break-apart” upon HO-1-catalyzed porphyrin degradation, perturbing the efficient FRET mechanism from a coumarin donor to a porphyrin acceptor fluorophore. Analysis of HO-1 activity using Escherichia coli lysates overexpressing hHO-1 found that a 6-fold increase in emission intensity at 383 nm was observed following incubation with NADPH. The identities of the degradation products following catabolism were confirmed by MALDI-MS and LC–MS, showing that porphyrin catabolism was regioselective at the α-position. Finally, through the analysis of Fe–L2, we have shown that close structural analogues of heme are required to maintain HO-1 activity. It is anticipated that this work will act as a foundation to design and develop new probes for HO-1 activity in the future, moving toward applications of live fluorescent imaging.
  • Journal article
    Bennett TLR, Wilkinson L, Lok JMA, O'Toole R, Long Net al., 2021,

    Synthesis, electrochemistry and optical properties of highly conjugated alkynyl-ferrocenes and -biferrocenes

    , Organometallics, Vol: 40, Pages: 1156-1162, ISSN: 0276-7333

    Sonogashira reactions are utilized herein to react iodo-ferrocenes and -biferrocenes with terminal alkyne ligands, functionalized with both pyridine and thioanisole groups. High-yielding reactions generate both monoalkynyl and dialkynyl derivatives, the ratio of which can be altered through changes in the reaction stoichiometry. This methodology allowed us to synthesize a large family of derivatives, comprising four symmetrical derivatives (3xx, where x represents a phenyl-substituted terminal alkyne) and six less-studied asymmetrical derivatives (3xy, where x and y represent two different phenyl-substituted terminal alkynes), as well as a number of their biferrocenyl analogues (6x, 7xx, and 7xy), including the first known examples of asymmetrically disubstituted biferrocenes. We examined the electrochemical behavior of all the systems in solution through the use of cyclic voltammetry and demonstrate that these highly conjugated alkynyl ligands exert delicate redox control over the central ferrocene motif. We also note that these substituents display some control over the mixed-valence character present in biferrocene monocations, with thioanisole substituents imparting almost an order of magnitude higher Kc than their pyridyl analogues, and asymmetric systems displaying rare characteristic properties of mixed-valence isomers. The electronic structure of these systems was further elucidated through a combination of UV/vis spectroscopy and density functional theory calculations. Our methodology provides a facile and adaptable route toward the isolation of a number of novel ferrocene and biferrocene derivatives. From our perspective, the asymmetric nature of these systems, along with the delicate and predictable redox control that these ligands exert on the central ferrocene unit(s), could lead to applications in molecular electronics, where these properties have previously shown promise in the fabrication of diodes and rectifiers, as well as in the synthesis of donor
  • Journal article
    Wang X, Ismael A, Almutlg A, Alshammari M, Al-Jobory A, Alshehab A, Bennett TLR, Wilkinson LA, Cohen LF, Long NJ, Robinson BJ, Lambert Cet al., 2021,

    Optimised power harvesting by controlling the pressure applied to molecular junctions

    , Chemical Science, Vol: 12, Pages: 5230-5235, ISSN: 2041-6520

    A major potential advantage of creating thermoelectric devices using self-assembled molecular layers is their mechanical flexibility. Previous reports have discussed the advantage of this flexibility from the perspective of facile skin attachment and the ability to avoid mechanical deformation. In this work, we demonstrate that the thermoelectric properties of such molecular devices can be controlled by taking advantage of their mechanical flexibility. The thermoelectric properties of self-assembled monolayers (SAMs) fabricated from thiol terminated molecules were measured with a modified AFM system, and the conformation of the SAMs was controlled by regulating the loading force between the organic thin film and the probe, which changes the tilt angle at the metal-molecule interface. We tracked the thermopower shift vs. the tilt angle of the SAM and showed that changes in both the electrical conductivity and Seebeck coefficient combine to optimize the power factor at a specific angle. This optimization of thermoelectric performance via applied pressure is confirmed through the use of theoretical calculations and is expected to be a general method for optimising the power factor of SAMs.
  • Journal article
    Omoruyi U, Page SJ, Apps S, White AJP, Long NJ, Miller PWet al., 2021,

    Synthesis and characterisation of a range of Fe, Co, Ru and Rh triphos complexes and investigations into the catalytic hydrogenation of levulinic acid

    , Journal of Organometallic Chemistry, Vol: 935, Pages: 1-12, ISSN: 0022-328X

    The coordination chemistry of the N-triphos ligand (NP3Ph, 1b) has been investigated with range of Fe, Co and Rh precursors and found to form either tridentate or bidentate complexes. Reaction of NP3Ph with [Rh(COD)(CH3CN)2]BF4 resulted in the formation of the tridentate complex [Rh(COD)(κ3 NP3Ph)]BF4 (3) in the solid state, however, in solution a bidentate complex predominates in more polar solvents. Reaction of NP3Ph with Fe carbonyl precursors revealed the formation of the bidentate complexes [Fe(CO)3(κ2-NP3Ph)Fe(CO)4] (4) and [Fe(CO)3(κ2-NP3Ph)] (5), while reaction with FeBr2 resulted in the paramagnetic bidentate complex [Fe(Br)2(κ2-NP3Ph)] (6). Reaction of NP3Ph with CoCl2 gave a dimeric Co species [(κ2-NP3Ph)CoCl(κ1,κ2-NP3Ph)CoCl3] (7), while Zn powder reduction of NP3Ph Co halides resulted in the formation of the tridentate complexes of the type: [Co(X)(k3-NP3Ph)]. The related triphos Ru complex, [Ru(CO3)(CO)(κ3-CP3Ph)] (2), has also been isolated and characterised. Preliminary catalytic hydrogenation of levulinic acid (LA) was conducted with 2 and 3. The Ru complex was found to be catalytically active, giving high conversions of LA to form gamma valerolactone (GVL) and 1,4-pentandiol (1,4-PDO), while 3 was found to be catalytically inactive. In situ catalytic testing with 1b and Fe(BF4)2.6H2O resulted in low conversions of LA while a combination of 1b and Co(BF4)2.6H2O gave higher conversions 75% yields of GVL.

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