Imperial College London

PROFESSOR NICHOLAS LONG

Faculty of Natural SciencesDepartment of Chemistry

Sir Edward Frankland BP Chair -Inorganic Chemistry
 
 
 
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Contact

 

+44 (0)20 7594 5781n.long Website CV

 
 
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Location

 

501jMolecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Publication Type
Year
to

280 results found

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, ISSN: 0044-8249

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, ISSN: 1433-7851

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

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

Boltersdorf T, Gavins FNE, Long NJ, 2021, Long-lived lanthanide emission via 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.

Journal article

Wang C, Sun W, Zhang J, Zhang J, Guo Q, Zhou X, Fan D, Liu H, Qi M, Gao X, Xu H, Gao Z, Tian M, Zhang H, Wang J, Wei Z, Long NJ, Mao Y, Li Cet al., 2021, An electric-field-responsive paramagnetic contrast agent enhances the visualization of epileptic foci in mouse models of drug-resistant epilepsy, NATURE BIOMEDICAL ENGINEERING, Vol: 5, Pages: 278-289, ISSN: 2157-846X

Journal article

Ismael A, Al-Jobory A, Wang X, Alshehab A, Almutlg A, Alshammari M, Grace I, Bennett TLR, Wilkinson LA, Robinson BJ, Long NJ, Lambert Cet al., 2021, Molecular-scale thermoelectricity: as simple as 'ABC' (vol 2, pg 5329, 2020), NANOSCALE ADVANCES, Vol: 3, Pages: 619-619, ISSN: 2516-0230

Journal article

Boyle J, Long NJ, Walter ERH, Ge Y, Mason JCet al., 2020, COMPOUNDS FOR THE DETECTION OF HEME OXYGENASE 1 (HO-1), AND METHODS AND USES INVOLVING THE SAME, 2017871.1

The present invention relates to compounds for the detection of heme oxygenase 1 (HO-1), in particular porphyrin, chlorin, bacteriochlorin or isobacteriochlorin compounds having a tetrapyrrole or reduced tetrapyrrole backbone and a fluorophore. Such compounds can be used in the detection of HO-1 in vivo, ex vivo and in vitro, and can also be used in methods of diagnosis and as research reagents.

Patent

Ismael A, Al-Jobory A, Wang X, Alshehab A, Almutlg A, Alshammari M, Grace I, Benett TLR, Wilkinson LA, Robinson BJ, Long NJ, Lambert Cet al., 2020, Molecular-scale thermoelectricity: as simple as 'ABC', NANOSCALE ADVANCES, Vol: 2, Pages: 5329-5334, ISSN: 2516-0230

Journal article

Morse SV, Boltersdorf T, Chan TG, Gavins FNE, Choi JJ, Long NJet al., 2020, In vivo delivery of a fluorescent FPR2/ALX-targeted probe using focused ultrasound and microbubbles to image activated microglia, RSC Chemical Biology, Vol: 1, Pages: 385-389, ISSN: 2633-0679

To image activated microglia, a small-molecule FPR2/ALX-targeted fluorescent probe was locally delivered into the brain using focused ultrasound and microbubbles. The probe did not co-localise with neurons or astrocytes but accumulated in activated microglia, making this a potential imaging tool for future drug discovery programs focused on neurological disorders.

Journal article

Seneviratne A, Han Y, Wong E, Walter E, Jiang L, Cave L, Long NJ, Carling D, Mason JC, Haskard DO, Boyle Jet al., 2020, Hematoma resolution in vivo is directed by Activating Transcription Factor 1, Circulation Research, Vol: 127, Pages: 928-944, ISSN: 0009-7330

Rationale: The efficient resolution of tissue hemorrhage is an important homeostatic function. In human macrophages in vitro, heme activates an adenosine monophosphate activated protein kinase / activating transcription factor 1 (AMPK/ATF1) pathway that directs Mhem macrophages through coregulation of heme oxygenase 1 (HMOX1, HO-1) and lipid homeostasis genes.Objective: We asked whether this pathway had an in vivo role in mice.Methods and Results: Perifemoral hematomas were used as a model of hematoma resolution. In mouse bone marrow derived macrophages (mBMM), heme induced HO-1, lipid regulatory genes including LXR, the growth factor IGF1, and the splenic red pulp macrophage gene Spic. This response was lost in mBMM from mice deficient in AMPK (Prkab1-/-) or ATF1 (Atf1-/-). In vivo, femoral hematomas resolved completely between day 8 and day 9 in littermate control mice (n=12), but were still present at day 9 in mice deficient in either AMPK (Prkab1-/-) or ATF1 (Atf1-/-) (n=6 each). Residual hematomas were accompanied by increased macrophage infiltration, inflammatory activation and oxidative stress. We also found that fluorescent lipids and a fluorescent iron-analog were trafficked to lipid-laden and iron-laden macrophages respectively. Moreover erythrocyte iron and lipid abnormally colocalized in the same macrophages in Atf1-/- mice. Therefore, iron-lipid separation was Atf1-dependent.Conclusions: Taken together, these data demonstrate that both AMPK and ATF1 are required for normal hematoma resolution.

Journal article

Evans RJ, Lavin B, Phinikaridou A, Chooi KY, Mohri Z, Wong E, Boyle JJ, Krams R, Botnar R, Long NJet al., 2020, Targeted molecular iron oxide contrast agents for imaging atherosclerotic plaque, Nanotheranostics, Vol: 4, Pages: 184-194, ISSN: 2206-7418

Overview: Cardiovascular disease remains a leading cause of death worldwide, with vulnerable plaque rupture the underlying cause of many heart attacks and strokes. Much research is focused on identifying an imaging biomarker to differentiate stable and vulnerable plaque. Magnetic Resonance Imaging (MRI) is a non-ionising and non-invasive imaging modality with excellent soft tissue contrast. However, MRI has relatively low sensitivity (micromolar) for contrast agent detection compared to nuclear imaging techniques. There is also an increasing emphasis on developing MRI probes that are not based on gadolinium chelates because of increasing concerns over associated systemic toxicity and deposits1. To address the sensitivity and safety concerns of gadolinium this project focused on the development of a high relaxivity probe based on superparamagnetic iron oxide nanoparticles for the imaging of atherosclerotic plaque with MRI. With development, this may facilitate differentiating stable and vulnerable plaque in vivo.Aim: To develop a range of MRI contrast agents based on superparamagnetic iron oxide nanoparticles (SPIONs), and test them in a murine model of advanced atherosclerosis.Methods: Nanoparticles of four core sizes were synthesised by thermal decomposition and coated with poly(maleicanhydride-alt-1-octadecene) (PMAO), poly(ethyleneimine) (PEI) or alendronate, then characterised for core size, hydrodynamic size, surface potential and relaxivity. On the basis of these results, one candidate was selected for further studies. In vivo studies using 10 nm PMAO-coated SPIONs were performed in ApoE-/- mice fed a western diet and instrumented with a perivascular cuff on the left carotid artery. Control ApoE-/- mice were fed a normal chow diet and were not instrumented. Mice were scanned on a 3T MR scanner (Philips Achieva) with the novel SPION contrast agent, and an elastin-targeted gadolinium agent that was shown previously to enable visualisation of plaque burden. Histo

Journal article

Cohen L, 2020, Tuning the thermoelectrical properties of anthracene-based self-assembled monolayers, Chemical Science, Vol: 11, Pages: 6836-6841, ISSN: 2041-6520

It is known that the electrical conductance of single molecules can be controlled in a deterministic manner by chemically varying their anchor groups to external electrodes. Here, by employing synthetic methodologies to vary the terminal anchor groups around aromatic anthracene cores, and by forming self-assembled monolayers (SAMs) of the resulting molecules, we demonstrate that this method of control can be translated into cross-plane SAM-on-gold molecular films. The cross-plane conductance of SAMs formed from anthracene-based molecules with four different combinations of anchors are measured to differ by a factor of approximately 3 in agreement with theoretical predictions. We also demonstrate that the Seebeck coefficient of such films can be boosted by more than an order of magnitude by an appropriate choice of anchor groups and that both positive and negative Seebeck coefficients can be realised. This demonstration that the thermoelectric properties of SAMs are controlled by their anchor groups represents a critical step towards functional ultra-thin-film devices for future molecular-scale electronics.

Journal article

Long NJ, 2020, Inorganic chemistry for PET radiolabelling: Ga-68- and F-18-based probes for mitochondria imaging, Publisher: WILEY, Pages: 359-359, ISSN: 0362-4803

Conference paper

Boltersdorf T, Ansari J, Senchenkova EY, Groeper J, Pajonczyk D, Vital SA, Kaur G, Alexander JS, Vogl T, Rescher U, Long NJ, Gavins FNEet al., 2020, Targeting of formyl peptide receptor 2 for in vivo imaging of acute vascular inflammation, Theranostics, Vol: 10, Pages: 6599-6614, ISSN: 1838-7640

Inflammatory conditions are associated with a variety of diseases and can significantly contribute to their pathophysiology. Neutrophils are recognised as key players in driving vascular inflammation and promoting inflammation resolution. As a result, neutrophils, and specifically their surface formyl peptide receptors (FPRs), are attractive targets for non-invasive visualization of inflammatory disease states and studying mechanistic details of the process.Methods: A small-molecule Formyl Peptide Receptor 2 (FPR2/ALX)-targeted compound was combined with two rhodamine-derived fluorescent tags to form firstly, a targeted probe (Rho-pip-C1) and secondly a targeted, pH-responsive probe (Rho-NH-C1) for in vivo applications. We tested internalization, toxicity and functional interactions with neutrophils in vitro for both compounds, as well as the fluorescence switching response of Rho-NH-C1 to neutrophil activation. Finally, in vivo imaging (fluorescent intravital microscopy [IVM]) and therapeutic efficacy studies were performed in an inflammatory mouse model.Results: In vitro studies showed that the compounds bound to human neutrophils via FPR2/ALX without causing internalization at relevant concentrations. Additionally, the compounds did not cause toxicity or affect neutrophil functional responses (e.g. chemotaxis or transmigration). In vivo studies using IVM showed Rho-pip-C1 bound to activated neutrophils in a model of vascular inflammation. The pH-sensitive (“switchable”) version termed Rho-NH-C1 validated these findings, showing fluorescent activity only in inflammatory conditions.Conclusions: These results indicate a viable design of fluorescent probes that have the ability to detect inflammatory events by targeting activated neutrophils.

Journal article

Wang X, Bennett TLR, Ismael A, Wilkinson LA, Hamill J, White AJP, Grace IM, Kolosov OV, Albrecht T, Robinson BJ, Long NJ, Cohen LF, Lambert CJet al., 2020, Scale-up of room-temperature constructive quantum interference from single molecules to self-assembled molecular-electronic films, Journal of the American Chemical Society, Vol: 142, Pages: 8555-8560, ISSN: 0002-7863

The realization of self-assembled molecular-electronic films, whose room-temperature transport properties are controlled by quantum interference (QI), is an essential step in the scale-up of QI effects from single molecules to parallel arrays of molecules. Recently, the effect of destructive QI (DQI) on the electrical conductance of self-assembled monolayers (SAMs) has been investigated. Here, through a combined experimental and theoretical investigation, we demonstrate chemical control of different forms of constructive QI (CQI) in cross-plane transport through SAMs and assess its influence on cross-plane thermoelectricity in SAMs. It is known that the electrical conductance of single molecules can be controlled in a deterministic manner, by chemically varying their connectivity to external electrodes. Here, by employing synthetic methodologies to vary the connectivity of terminal anchor groups around aromatic anthracene cores, and by forming SAMs of the resulting molecules, we clearly demonstrate that this signature of CQI can be translated into SAM-on-gold molecular films. We show that the conductance of vertical molecular junctions formed from anthracene-based molecules with two different connectivities differ by a factor of approximately 16, in agreement with theoretical predictions for their conductance ratio based on CQI effects within the core. We also demonstrate that for molecules with thioether anchor groups, the Seebeck coefficient of such films is connectivity dependent and with an appropriate choice of connectivity can be boosted by ∼50%. This demonstration of QI and its influence on thermoelectricity in SAMs represents a critical step toward functional ultra-thin-film devices for future thermoelectric and molecular-scale electronics applications.

Journal article

Clough TJ, Baxan N, Coakley EJ, Rivas C, Zhao L, Leclerc I, Martinez-Sanchez A, Rutter GA, Long NJet al., 2020, Synthesis and in vivo behaviour of an exendin-4-based MRI probe capable of beta-cell-dependent contrast enhancement in the pancreas, Dalton Transactions: an international journal of inorganic chemistry, Vol: 49, Pages: 4732-4740, ISSN: 1477-9226

Global rates of diabetes mellitus are increasing, and treatment of the disease consumes a growing proportion of healthcare spending across the world. Pancreatic β-cells, responsible for insulin production, decline in mass in type 1 and, to a more limited degree, in type 2 diabetes. However, the extent and rate of loss in both diseases differs between patients resulting in the need for the development of novel diagnostic tools, which could quantitatively assess changes in mass of β-cells over time and potentially lead to earlier diagnosis and improved treatments. Exendin-4, a potent analogue of glucagon-like-peptide 1 (GLP-1), binds to the receptor GLP-1R, whose expression is enriched in β-cells. GLP-1R has thus been used in the past as a means of targeting probes for a wide variety of imaging modalities to the endocrine pancreas. However, exendin-4 conjugates designed specifically for MRI contrast agents are an under-explored area. In the present work, the synthesis and characterization of an exendin-4-dota(ga)-Gd(III) complex, GdEx, is reported, along with its in vivo behaviour in healthy and in β-cell-depleted C57BL/6J mice. Compared to the ubiquitous probe, [Gd(dota)]−, GdEx shows selective uptake by the pancreas with a marked decrease in accumulation observed after the loss of β-cells elicited by deleting the microRNA processing enzyme, DICER. These results open up pathways towards the development of other targeted MRI contrast agents based on similar chemistry methodology.

Journal article

Gawne PJ, Clarke F, Turjeman K, Cope AP, Long NJ, Barenholz Y, Terry SYA, de Rosales RTMet al., 2020, PET imaging of liposomal glucocorticoids using Zr-89-oxine: theranostic applications in inflammatory arthritis, Theranostics, Vol: 10, Pages: 3867-3879, ISSN: 1838-7640

The encapsulation of Glucocorticoids (GCs) into long-circulating liposomes (LCLs) is a proven strategy to reduce the side effects of glucocorticoids and improve the treatment of inflammatory diseases, such as rheumatoid arthritis (RA). With the aim of supporting the development of GC-loaded LCLs, and potentially predict patient response to therapy clinically, we evaluated a direct PET imaging radiolabelling approach for preformed GC-LCLs in an animal model of human inflammatory arthritis.Methods: A preformed PEGylated liposomal methylprednisolone hemisuccinate (NSSL-MPS) nanomedicine was radiolabelled using [89Zr]Zr(oxinate)4 (89Zr-oxine), characterised and tracked in vivo using PET imaging in a K/BxN serum-transfer arthritis (STA) mouse model of inflammatory arthritis and non-inflamed controls. Histology and joint size measurements were used to confirm inflammation. The biodistribution of 89Zr-NSSL-MPS was compared to that of free 89Zr in the same model. A therapeutic study using NSSL-MPS using the same time points as the PET/CT imaging was carried out.Results: The radiolabelling efficiency of NSSL-MPS with [89Zr]Zr(oxinate)4 was 69 ± 8 %. PET/CT imaging of 89Zr-NSSL-MPS showed high uptake (3.6 ± 1.5 % ID; 17.4 ± 9.3 % ID/mL) at inflamed joints, with low activity present in non-inflamed joints (0.5 ± 0.1 % ID; 2.7 ± 1.1 % ID/mL). Importantly, a clear correlation between joint swelling and high 89Zr-NSSL-MPS uptake was observed, which was not observed with free 89Zr. STA mice receiving a therapeutic dose of NSSL-MPS showed a reduction in inflammation at the time points used for the PET/CT imaging compared with the control group.Conclusions: PET imaging was used for the first time to track a liposomal glucocorticoid, showing high uptake at visible and occult inflamed sites and a good correlation with the degree of inflammation. A subsequent therapeutic response matching imaging time points in the same model demonstrated the potentia

Journal article

Morse SV, Boltersdorf T, Harriss BI, Chan TG, Baxan N, Hee Seok J, Pouliopoulos AN, Choi J, Long NJet al., 2020, Neuron labeling with rhodamine-conjugated Gd-based MRI contrast agents delivered to the brain via focused ultrasound, Theranostics, Vol: 10, Pages: 2659-2674, ISSN: 1838-7640

Gadolinium-based magnetic resonance imaging contrast agents can provide information regarding neuronal function, provided that these agents can cross the neuronal cell membrane. Such contrast agents are normally restricted to extracellular domains, however, by attaching cationic fluorescent dyes, they can be made cell-permeable and allow for both optical and magnetic resonance detection. To reach neurons, these agents also need to cross the blood-brain barrier. Focused ultrasound combined with microbubbles has been shown to enhance the permeability of this barrier, allowing molecules into the brain non-invasively, locally and transiently. The goal of this study was to investigate whether combining fluorescent rhodamine with a gadolinium complex would form a dual-modal contrast agent that could label neurons in vivo when delivered to the mouse brain with focused ultrasound and microbubbles.Methods: Gadolinium complexes were combined with a fluorescent, cationic rhodamine unit to form probes with fluorescence and relaxivity properties suitable for in vivo applications. The left hemisphere of female C57bl/6 mice (8-10 weeks old; 19.07 ± 1.56 g; n = 16) was treated with ultrasound (centre frequency: 1 MHz, peak-negative pressure: 0.35 MPa, pulse length: 10 ms, repetition frequency: 0.5 Hz) while intravenously injecting SonoVue microbubbles and either the 1 kDa Gd(rhodamine-pip-DO3A) complex or a conventionally-used lysine-fixable Texas Red® 3 kDa dextran. The opposite right hemisphere was used as a non-treated control region. Brains were then extracted and either sectioned and imaged via fluorescence or confocal microscopy or imaged using a 9.4 T magnetic resonance imaging scanner. Brain slices were stained for neurons (NeuN), microglia (Iba1) and astrocytes (GFAP) to investigate the cellular localization of the probes.Results: Rhodamine fluorescence was detected in the left hemisphere of all ultrasound treated mice, while none was detected in the right contr

Journal article

Smith AJ, Osborne BE, Keeling GP, Blower PJ, Southworth R, Long NJet al., 2020, DO2A-based ligands for gallium-68 chelation: synthesis, radiochemistry and ex vivo cardiac uptake, DALTON TRANSACTIONS, Vol: 49, Pages: 1097-1106, ISSN: 1477-9226

Journal article

Jiang L, Lung HL, Huang T, Lan R, Zha S, Chan LS, Thor W, Tsoi T, Chau H, Boreström C, Cobb S, Tsao SW, Bian Z, Law G, Wong W, Tai WC, Chau YW, Du Y, Tang LHX, Chiang AKS, Middeldorp JM, Lo K, Mak N, Long N, Wong Ket al., 2019, Reactivation of Epstein Barr virus by a dual-responsive fluorescent EBNA1-targeting agent with Zn2+-chelating function., Proceedings of the National Academy of Sciences of USA, Vol: 116, Pages: 26614-26624, ISSN: 0027-8424

Epstein-Barr nuclear antigen 1 (EBNA1) plays a vital role in the maintenance of the viral genome, and is the only viral protein expressed in nearly all forms of EBV latency and EBV-associated diseases including numerous cancer types. To our knowledge, no specific agent against Epstein Barr virus (EBV) genes or proteins has been established to target EBV lytic reactivation. Here we report an EBNA1- and Zn2+- responsive probe (ZRL5P4), which alone could reactivate EBV lytic cycle through specific disruption of EBNA1. We have utilized the Zn2+ chelator to further interfere with the higher order of EBNA1 self-association. The new bioprobe ZRL5P4 can respond independently to its interactions with Zn2+ and EBNA1 with different fluorescence changes. It can selectively enter the nuclei of EBV-positive cells and disrupt the oligomerization and oriP-enhanced transactivation of EBNA1. ZRL5P4 can also specifically enhance Dicer1 and PML expression, molecular events which had been reported to occur after the depletion of EBNA1 expression. Importantly, we found that the treatment with ZRL5P4-alone could reactivate the EBV lytic induction by expressing the early and late EBV lytic genes/proteins. The lytic induction is likely mediated by disruption of EBNA1 oligomerization and the subsequent change of Dicer1 expression. Our new probe ZRL5P4 represents the first EBV protein-specific agent to potently reactivate EBV from latency, leading to the shrinkage of EBV-positive tumours, and our study also suggests the association of EBNA1 oligomerization with the maintenance of EBV latency.

Journal article

McCluskey S, Haslop A, Coello C, Gunn R, Tate E, Southworth R, Plisson C, Long NJ, Wells Let al., 2019, Imaging chemotherapy induced acute cardiotoxicity with 18F-labelled lipophilic cations, Journal of Nuclear Medicine, Vol: 60, Pages: 1750-1756, ISSN: 1535-5667

Many chemotherapy agents are toxic to the heart, such that increasing numbers of cancer survivors are now living with the potentially lethal cardiovascular consequences of their treatment. Earlier and more sensitive detection of chemotherapy-induced cardiotoxicity may allow improved treatment strategies and increase long-term survival. Lipophilic cation positron emission tomography (PET) tracers may be suitable for early detection of cardiotoxicity. This study aims to evaluate an 18F-labelled lipophilic phosphonium cation e.g. 18F-Mitophos, as a cardiac imaging agent, comparing it to leading PET and SPECT lipophilic cationic tracers before further assessing its potential for imaging cardiotoxicity in an acute doxorubicin (DOX) model.

Journal article

Boltersdorf T, Ansari J, Senchenkova EY, Jiang L, White AJP, Coogan M, Gavins FNE, Long NJet al., 2019, Development, characterisation and in vitro evaluation of lanthanide-based FPR2/ALX-targeted imaging probes., Dalton Trans, Vol: 48, Pages: 16764-16775

We report the design, preparation and characterisation of three small-molecule, Formyl Peptide Receptor (FPR)-targeted lanthanide complexes (Tb·14, Eu·14 and Gd·14). Long-lived, metal-based emission was observed from the terbium complex (τH2O = 1.9 ms), whereas only negligible lanthanide signals were detected in the europium analogue. Ligand-centred emission was investigated using Gd·14 at room temperature and 77 K, leading to the postulation that metal emission may be sensitised via a ligand-based charge transfer state of the targeting Quin C1 unit. Comparatively high longitudinal relaxivity values (r1) for octadentate metal complexes of Gd·14 were determined (6.9 mM-1 s-1 at 400 MHz and 294 K), which could be a result of a relative increase in twisted square antiprism (TSAP) isomer prevalence compared to typical DOTA constructs (as evidenced by NMR spectroscopy). In vitro validation of concentration responses of Tb·14via three key neutrophil functional assays demonstrated that the inflammatory responses of neutrophils (i.e. chemotaxis, transmigration and granular release) remained unchanged in the presence of specific concentrations of the compound. Using a time-resolved microscopy set-up we were able to observe binding of the Tb·14 probe to stimulated human neutrophils around the cell periphery, while in the same experiment with un-activated neutrophils, no metal-based signals were detected. Our results demonstrate the utility of Tb·14 for time-resolved microscopy with lifetimes several orders of magnitude longer than autofluorescent signals and a preferential uptake in stimulated neutrophils.

Journal article

Xie C, Chau H-F, Zhang J-X, Tong S, Jiang L, Fok W-Y, Lung H-L, Zha S, Zou R, Jiao J, Ng C-F, Ma P, Zhang J, Lin J, Shiu KK, Bunzli J-CG, Wong W-K, Long NJ, Law G-L, Wong K-Let al., 2019, Bladder Cancer Photodynamic Therapeutic Agent with Off-On Magnetic Resonance Imaging Enhancement, ADVANCED THERAPEUTICS, Vol: 2

Journal article

Mundil R, Wilson LE, Schaarschmidt D, Císařová I, Merna J, Long NJet al., 2019, Redox-switchable α-diimine palladium catalysts for control of polyethylene topology, Polymer, Vol: 179, ISSN: 0032-3861

A series of palladium complexes bearing ferrocene substituted α-diimine ligands was synthesized and investigated for ethene polymerization at different conditions to modulate the extent of “chain-walking” mechanism and regulate branching and topology of resulting polyethylenes. All ferrocene substituted complexes catalyzed living/controlled ethene polymerization. The ability of ferrocene substituted palladium complexes to provide polyethylenes with dendritic topology was proved by measuring their Mark-Houwink plots. In-situ chemical oxidation of ferrocene moieties via silver triflate was used to affect the catalyst electronic structure and support the “chain-walking” mechanism. Oxidation of palladium catalyst led to its destabilization while the catalytic activity of newly formed sites was substantially increased. It was demonstrated that catalyst oxidation is a powerful tool to regulate the topology of resulting polyethylenes.

Journal article

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