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Baark F, Waters ECT, Eykyn TR, Southworth R. Characterization and Validation of Radiotracer Kinetics Using the Langendorff Isolated Perfused Heart. Methods Mol Biol 2024; 2729:251-267. [PMID: 38006501 DOI: 10.1007/978-1-0716-3499-8_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2023]
Abstract
The Langendorff isolated perfused heart is a physiologically relevant and controllable ex vivo model well suited to characterizing and validating novel radiotracers for a wide range of molecular imaging applications. It allows the monitoring of first pass tracer uptake kinetics either as a bolus injection or as a continuous infusion in beating myocardial tissue with a high degree of experimental control in terms of cardiac workload, perfusion, energy substrate delivery and composition, and drug co-administration. The radiotracer pharmacokinetic data that it provides is not contaminated by confounding factors such as off-target tracer metabolism, and as a non-imaging technique, time activity curves can be acquired with very high temporal resolution. In this chapter, we describe the basic principles and practice for setting up and using Langendorff isolated perfused hearts for the assessment of novel radiotracers and outline their potential for modeling pathophysiological conditions relevant to cardiovascular disease.
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Affiliation(s)
- Friedrich Baark
- School of Biomedical Engineering and Imaging Sciences, King's College London, St Thomas' Hospital, London, UK
| | - Edward C T Waters
- School of Biomedical Engineering and Imaging Sciences, King's College London, St Thomas' Hospital, London, UK
| | - Thomas R Eykyn
- School of Biomedical Engineering and Imaging Sciences, King's College London, St Thomas' Hospital, London, UK
| | - Richard Southworth
- School of Biomedical Engineering and Imaging Sciences, King's College London, St Thomas' Hospital, London, UK.
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Ong HC, Coimbra JTS, Ramos MJ, Xing B, Fernandes PA, García F. Beyond the TPP + "gold standard": a new generation mitochondrial delivery vector based on extended PN frameworks. Chem Sci 2023; 14:4126-4133. [PMID: 37063789 PMCID: PMC10094279 DOI: 10.1039/d2sc06508h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 02/13/2023] [Indexed: 02/17/2023] Open
Abstract
Mitochondrial targeting represents an attractive strategy for treating metabolic, degenerative and hyperproliferative diseases, since this organelle plays key roles in essential cellular functions. Triphenylphosphonium (TPP+) moieties - the current "gold standard" - have been widely used as mitochondrial targeting vectors for a wide range of molecular cargo. Recently, further optimisation of the TPP+ platform drew considerable interest as a way to enhance mitochondrial therapies. However, although the modification of this system appears promising, the core structure of the TPP+ moiety remains largely unchanged. Thus, this study explored the use of aminophosphonium (PN+) and phosphazenylphosphonium (PPN+) main group frameworks as novel mitochondrial delivery vectors. The PPN+ moiety was found to be a highly promising platform for this purpose, owing to its unique electronic properties and high lipophilicity. This has been demonstrated by the high mitochondrial accumulation of a PPN+-conjugated fluorophore relative to its TPP+-conjugated counterpart, and has been further supported by density functional theory and molecular dynamics calculations, highlighting the PPN+ moiety's unusual electronic properties. These results demonstrate the potential of novel phosphorus-nitrogen based frameworks as highly effective mitochondrial delivery vectors over traditional TPP+ vectors.
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Affiliation(s)
- How Chee Ong
- School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University 21 Nanyang Link 637371 Singapore
| | - João T S Coimbra
- LAQV/REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto Rua do Campo Alegre 687, s/n 4169-007 Porto Portugal
| | - Maria J Ramos
- LAQV/REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto Rua do Campo Alegre 687, s/n 4169-007 Porto Portugal
| | - Bengang Xing
- School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University 21 Nanyang Link 637371 Singapore
| | - Pedro A Fernandes
- LAQV/REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto Rua do Campo Alegre 687, s/n 4169-007 Porto Portugal
| | - Felipe García
- Departamento de Química Orgánica e Inorgánica, Facultad de Química, Universidad de Oviedo Avda Julian Claveria 8 33006 Asturias Spain
- School of Chemistry, Monash University Clayton Victoria 3800 Australia
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Radiochemistry with {Al18F}2+: Current status and optimization perspectives for efficient radiofluorination by complexation. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2023.215028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Ong HC, Coimbra JTS, Kwek G, Ramos MJ, Xing B, Fernandes PA, García F. Alkyl vs. aryl modifications: a comparative study on modular modifications of triphenylphosphonium mitochondrial vectors. RSC Chem Biol 2021; 2:1643-1650. [PMID: 34977579 PMCID: PMC8637833 DOI: 10.1039/d1cb00099c] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 08/21/2021] [Indexed: 11/21/2022] Open
Abstract
Triphenylphosphonium (TPP+) moieties are commonly conjugated to drug molecules to confer mitochondrial selectivity due to their positive charge and high lipophilicity. Although optimisation of lipophilicity can be achieved by modifying the length of the alkyl linkers between the TPP+ moiety and the drug molecule, it is not always possible. While methylation of the TPP+ moiety is a viable alternative to increase lipophilicity and mitochondrial accumulation, there are no studies comparing these two separate modular approaches. Thus, we have systematically designed, synthesised and tested a range of TPP+ molecules with varying alkyl chain lengths and degree of aryl methylation to compare the two modular methodologies for modulating lipophilicity. The ability of aryl/alkyl modified TPP+ to deliver cargo to the mitochondria was also evaluated by confocal imaging with a TPP+-conjugated fluorescein-based fluorophore. Furthermore, we have employed molecular dynamics simulations to understand the translocation of these molecules through biological membrane model systems. These results provide further insights into the thermodynamics of this process and the effect of alkyl and aryl modular modifications. Alkyl chain extension and aryl methylation can be employed to enhance mitochondrial uptake in triphenylphosphonium vectors. Here we compare these complementary strategies and their mitochondrial-targeting effects using a modular synthetic approach.![]()
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Affiliation(s)
- How Chee Ong
- School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University 21 Nanyang Link 637371 Singapore
| | - João T S Coimbra
- LAQV, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto Rua do Campo Alegre s/n 4169-007 Portugal
| | - Germain Kwek
- School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University 21 Nanyang Link 637371 Singapore
| | - Maria J Ramos
- LAQV, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto Rua do Campo Alegre s/n 4169-007 Portugal
| | - Bengang Xing
- School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University 21 Nanyang Link 637371 Singapore
| | - Pedro A Fernandes
- LAQV, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto Rua do Campo Alegre s/n 4169-007 Portugal
| | - Felipe García
- School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University 21 Nanyang Link 637371 Singapore
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5
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Osborne BE, Yue TTC, Waters ECT, Baark F, Southworth R, Long NJ. Synthesis and ex vivo biological evaluation of gallium-68 labelled NODAGA chelates assessing cardiac uptake and retention. Dalton Trans 2021; 50:14695-14705. [PMID: 34585706 DOI: 10.1039/d1dt02224e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Radiolabelled lipophilic cations can be used to non-invasively report on mitochondrial dysfunction in diseases such as cardiovascular disease, cardiotoxicity and cancer. Several such lipophilic cations are currently used clinically to map myocardial perfusion using SPECT imaging. Since PET offers significant advantages over SPECT in terms of sensitivity, resolution and the capacity for dynamic imaging to allow pharmacokinetic modelling, we have synthesised and radiolabelled a series of NODAGA-based radiotracers, with triarylphosphonium-functionalisation, with gallium-68 to develop PET-compatible cationic complexes. To evaluate their capacity to report upon mitochondrial membrane potential, we assessed their pharmacokinetic profiles in isolated perfused rat hearts before and after mitochondrial depolarisation with the ionophore CCCP. All three tracers radiolabel with over 96% RCY, with log D7.4 values above -0.4 observed for the most lipophilic example of this family of radiotracers. The candidate tracer [68Ga]Ga4c exhibited non-preferential uptake in healthy cardiac tissue over CCCP-infused cardiac tissue. While this approach does show promise, the lipophilicity of this family of probes needs improving in order for them to be effective cardiac imaging agents.
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Affiliation(s)
- Bradley E Osborne
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London, W12 0BZ, UK.
- School of Biomedical Engineering and Imaging Sciences, King's College London, 4th Floor Lambeth Wing, St Thomas' Hospital, London, SE1 7EH, UK.
| | - Thomas T C Yue
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London, W12 0BZ, UK.
| | - Edward C T Waters
- School of Biomedical Engineering and Imaging Sciences, King's College London, 4th Floor Lambeth Wing, St Thomas' Hospital, London, SE1 7EH, UK.
| | - Friedrich Baark
- School of Biomedical Engineering and Imaging Sciences, King's College London, 4th Floor Lambeth Wing, St Thomas' Hospital, London, SE1 7EH, UK.
| | - Richard Southworth
- School of Biomedical Engineering and Imaging Sciences, King's College London, 4th Floor Lambeth Wing, St Thomas' Hospital, London, SE1 7EH, UK.
| | - Nicholas J Long
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London, W12 0BZ, UK.
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Walter ERH, Cooper SM, Boyle JJ, Long NJ. Enzyme-activated probes in optical imaging: a focus on atherosclerosis. Dalton Trans 2021; 50:14486-14497. [PMID: 34605500 PMCID: PMC8546924 DOI: 10.1039/d1dt02198b] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 09/27/2021] [Indexed: 12/16/2022]
Abstract
Enzyme-activated probes enable complex biological processes to be studied in real-time. A wide range of enzymes are modulated in diseases, including cancer, inflammatory diseases and cardiovascular disease, and have the potential to act as vital diagnostic and prognostic biomarkers to monitor and report on disease progression. In this perspective article, we discuss suitable design characteristics of enzyme-activated fluorescent probes for ex vivo and in vivo optical imaging applications. With a particular focus on atherosclerosis imaging, we highlight recent approaches to report on the activity of cathepsins (K and B), matrix metalloproteinases (MMP-2 and MMP-9), thrombin, heme oxygenase-1 (HO-1) and myeloperoxidase (MPO).
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Affiliation(s)
- Edward R H Walter
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 0BZ, UK.
- National Heart and Lung Institute, Imperial College London, London, W12 0NN, UK
| | - Saul M Cooper
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 0BZ, UK.
- National Heart and Lung Institute, Imperial College London, London, W12 0NN, UK
| | - Joseph J Boyle
- National Heart and Lung Institute, Imperial College London, London, W12 0NN, UK
| | - Nicholas J Long
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 0BZ, UK.
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Sneddon D, Cornelissen B. Emerging chelators for nuclear imaging. Curr Opin Chem Biol 2021; 63:152-162. [PMID: 34051509 DOI: 10.1016/j.cbpa.2021.03.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 02/28/2021] [Accepted: 03/09/2021] [Indexed: 11/25/2022]
Abstract
Chelators are necessary in nuclear medicine imaging to direct an inorganic radionuclide, a radiometal, to a desired target; unfortunately, there is no 'one-size-fits-all' chelator. As the toolbox of radiometals is expanding, new chelators are required to prevent off-target side effects. 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) is the current gold standard chelator for several radiometals, but typically, chelation requires harsh conditions, making it unsuitable to label biological vectors. The ideal chelator would allow labelling under mild conditions (near-neutral pH and low temperatures [∼37 °C]) and be both thermodynamically and kinetically stable. Over the past 2-3 years, several exciting chelators have been developed that have superior properties to make them worth investigating for future clinical applications.
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Affiliation(s)
- Deborah Sneddon
- MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, OX3 7LE, United Kingdom.
| | - Bart Cornelissen
- MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, OX3 7LE, United Kingdom
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