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Biller JR, McPeak JE. EPR Everywhere. APPLIED MAGNETIC RESONANCE 2021; 52:1113-1139. [PMID: 33519097 PMCID: PMC7826499 DOI: 10.1007/s00723-020-01304-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 10/16/2020] [Accepted: 12/06/2020] [Indexed: 06/12/2023]
Abstract
This review is inspired by the contributions from the University of Denver group to low-field EPR, in honor of Professor Gareth Eaton's 80th birthday. The goal is to capture the spirit of innovation behind the body of work, especially as it pertains to development of new EPR techniques. The spirit of the DU EPR laboratory is one that never sought to limit what an EPR experiment could be, or how it could be applied. The most well-known example of this is the development and recent commercialization of rapid-scan EPR. Both of the Eatons have made it a point to remain knowledgeable on the newest developments in electronics and instrument design. To that end, our review touches on the use of miniaturized electronics and applications of single-board spectrometers based on software-defined radio (SDR) implementations and single-chip voltage-controlled oscillator (VCO) arrays. We also highlight several non-traditional approaches to the EPR experiment such as an EPR spectrometer with a "wand" form factor for analysis of the OxyChip, the EPR-MOUSE which enables non-destructive in situ analysis of many non-conforming samples, and interferometric EPR and frequency swept EPR as alternatives to classical high Q resonant structures.
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Affiliation(s)
| | - Joseph E. McPeak
- University of Denver, Denver, CO 80210 USA
- Berlin Joint EPR Laboratory and EPR4Energy, Department Spins in Energy Conversion and Quantum Information Science (ASPINS), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
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2
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Abstract
Regulation of ATP production by mitochondria, critical to multicellular life, is poorly understood. Here we investigate the molecular controls of this process in heart and provide a framework for its Ca2+-dependent regulation. We find that the entry of Ca2+ into the matrix through the mitochondrial calcium uniporter (MCU) in heart has neither an apparent cytosolic Ca2+ threshold nor gating function and guides ATP production by its influence on the inner mitochondrial membrane (IMM) potential, ΔΨm. This regulation occurs by matrix Ca2+-dependent modulation of pyruvate and glutamate dehydrogenase activity and not through any effect of Ca2+ on ATP Synthase or on Electron Transport Chain Complexes II, III or IV. Examining the ΔΨm dependence of ATP production over the range of -60 mV to -170 mV in detail reveals that cardiac ATP synthase has a voltage dependence that distinguishes it fundamentally from the previous standard, the bacterial ATP synthase. Cardiac ATP synthase operates with a different ΔΨm threshold for ATP production than bacterial ATP synthase and reveals a concave-upwards shape without saturation. Skeletal muscle MCU Ca2+ flux, while also having no apparent cytosolic Ca2+ threshold, is substantially different from the cardiac MCU, yet the ATP synthase voltage dependence in skeletal muscle is identical to that in the heart. These results suggest that while the conduction of cytosolic Ca2+ signals through the MCU appears to be tissue-dependent, as shown by earlier work1, the control of ATP synthase by ΔΨm appears to be broadly consistent among tissues but is clearly different from bacteria.
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Affiliation(s)
- Andrew P Wescott
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Joseph P Y Kao
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - W Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Liron Boyman
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA.
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.
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3
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Russo J, Litz M, Ray W, Bayne S, Rosen GM, Cho H, Yu J, Bigio DI, Thomas C, Alam TR. Demonstration of a Tritiated Nitroxide Nuclear Battery. Appl Radiat Isot 2018; 144:93-103. [PMID: 30572201 DOI: 10.1016/j.apradiso.2018.10.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 10/07/2018] [Accepted: 10/09/2018] [Indexed: 11/26/2022]
Abstract
Unattended, compact, terrestrial and space sensors require sources that have high energy and power densities to continuously operate for 3 to 99 years depending on application. Currently, chemical sources cannot fully satisfy these applications, especially in solid state form. Betavoltaic (βV) nuclear batteries using β--emitting radioisotopes possess energy densities 1000 times greater than conventional chemical sources. Their power density is a function of β- flux saturation point relative to the planar (2D) configuration, β- emission range, and the semiconductor converter, the betavoltaic (βV) cell, properties. The figure of merit is the beta (β-)-flux surface power density ( [Formula: see text] in μWn per cm2 footprint), where an optimal portion of incident beta particles penetrates the surrounding semiconductor depletion region. Tritiated nitroxides are favorable radioisotope sources with the potential to have the highest specific activity (Am in Ci/g) and [Formula: see text] for an organic compound in solid form. The goal of this research is to demonstrate a tritiated nitroxide nuclear battery using the planar (2D) coupling configuration. The reproducible tritiation procedure produced stable product with a Am of approximately 635 Ci/g, which was 70% of the theoretical Am. For the nuclear battery demonstration, the tritiated nitroxide, dissolved in methanol, was deposited on a 4H-SiC βV and InGaP photovoltaic (PV) cell using a dispensing apparatus and micropipette. Both devices' characteristics were measured beforehand using a controlled electron beam source to approximate the surface radioactivity from the deposited radioisotope. The maximum power point (MPP) of the 4H-SiC and InGaP were 7.77 nW/cm2 and 1.63 nW/cm2 with 100 mCi and 67 mCi, respectively. The power and total efficiency were lower than expected due to partial solvent evaporation and droplet thickness. Numerical models using MCNP6 Monte Carlo code were used to simulate an optimal nuclear battery prototype. The models' accuracy was confirmed with the device calibration curves and a previous metal tritide model based on empirical results. Based on optimal model results, the tritiated nitroxide saturation layer thickness (D0.99) and [Formula: see text] (D0.99) were 10 µm and 558 nW/cm2, respectively, using a 4H-SiC.
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Affiliation(s)
- Johnny Russo
- Sensors and Electron Devices Directorate, US Army Research Laboratory, Adelphi, MD 20783; Department of Mechanical Engineering, University of Maryland, College Park, MD 20742.
| | - Marc Litz
- Sensors and Electron Devices Directorate, US Army Research Laboratory, Adelphi, MD 20783.
| | - William Ray
- Sensors and Electron Devices Directorate, US Army Research Laboratory, Adelphi, MD 20783; Oak Ridge Associated Universities (ORAU), Oak Ridge, TN 37831; Department of Electrical Engineering, Texas Tech University, Lubbock, TX 79409.
| | - Stephen Bayne
- Department of Electrical Engineering, Texas Tech University, Lubbock, TX 79409.
| | - Gerald M Rosen
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201.
| | - Hansol Cho
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742.
| | - Joshua Yu
- Department of Electrical Engineering, University of Maryland, College Park, MD 20742.
| | - David I Bigio
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742.
| | | | - Tariq Rizvi Alam
- The Pennsylvania State University, University Park, PA 16802; Defense Threat Reduction Agency (DTRA), Fort Belvoir, VA 22060.
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Cornes SP, Zhou S, Porfyrakis K. Synthesis and EPR studies of the first water-soluble N@C 60 derivative. Chem Commun (Camb) 2017; 53:12742-12745. [PMID: 29115325 DOI: 10.1039/c7cc07106j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The first water-soluble derivative of the paramagnetic endohedral fullerene N@C60 has been prepared through the covalent attachment of a single addend containing two permethylated β-cyclodextrin units to the surface of the carbon cage. The line width of the derivative's EPR signal is highly sensitive to both the nature of the solvent and the presence of Cu(ii) ions in solution.
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Affiliation(s)
- Stuart P Cornes
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK.
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Russo J, Litz M, Ray W, Rosen GM, Bigio DI, Fazio R. Development of tritiated nitroxide for nuclear battery. Appl Radiat Isot 2017; 125:66-73. [DOI: 10.1016/j.apradiso.2017.04.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 03/24/2017] [Accepted: 04/04/2017] [Indexed: 11/15/2022]
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Liu F, Shen YC, Ouyang YH, Yan GP, Chen S, Liu H, Wu YG, Wu JY. Synthesis and Properties of Isoindoline Nitroxide-containing Porphyrins. J Heterocycl Chem 2017. [DOI: 10.1002/jhet.2928] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Fan Liu
- School of Material Science and Engineering; Wuhan Institute of Technology; Wuhan 430074 China
| | - Yan-Chun Shen
- School of Material Science and Engineering; Wuhan Institute of Technology; Wuhan 430074 China
| | - Yao-Hua Ouyang
- School of Material Science and Engineering; Wuhan Institute of Technology; Wuhan 430074 China
| | - Guo-Ping Yan
- School of Material Science and Engineering; Wuhan Institute of Technology; Wuhan 430074 China
| | - Si Chen
- School of Material Science and Engineering; Wuhan Institute of Technology; Wuhan 430074 China
| | - Hui Liu
- School of Material Science and Engineering; Wuhan Institute of Technology; Wuhan 430074 China
| | - Yan-Guang Wu
- School of Material Science and Engineering; Wuhan Institute of Technology; Wuhan 430074 China
| | - Jiang-Yu Wu
- School of Material Science and Engineering; Wuhan Institute of Technology; Wuhan 430074 China
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Abstract
Molecular oxygen (O2) is essential to brain function and mechanisms necessary to regulate variations in delivery or utilization of O2 are crucial to support normal brain homeostasis, physiology and energy metabolism. Any imbalance in cerebral tissue partial pressure of O2 (pO2) levels may lead to pathophysiological complications including increased reactive O2 species generation leading to oxidative stress when tissue O2 level is too high or too low. Accordingly, the need for oximetry methods, which assess cerebral pO2in vivo and in real time, is imperative to understand the role of O2 in various metabolic and disease states, including the effects of treatment and therapy options. In this review, we provide a brief overview of the common in vivo oximetry methodologies for measuring cerebral pO2. We discuss the advantages and limitations of oximetry methodologies to measure cerebral pO2in vivo followed by a more in-depth review of electron paramagnetic resonance oximetry spectroscopy and imaging using several examples of current electron paramagnetic resonance oximetry applications in the brain.
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Affiliation(s)
- John M Weaver
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.,Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, USA
| | - Ke Jian Liu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.,Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.,Department of Neurology, University of New Mexico Health Sciences Center, Albuquerque, NM, USA
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Liu F, Zou TJ, Tan ZL, Chen S, Wu ZH, Yan GP, Zhang Q, Liang SC, Yang J. Isoindoline nitroxide-labeled porphyrins as potential fluorescence-suppressed spin probes. Org Biomol Chem 2017; 15:1245-1253. [PMID: 28098314 DOI: 10.1039/c6ob02748b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A series of isoindoline nitroxide-labeled porphyrins were synthesized by the reaction of 5-phenyldipyrromethane and 5-(4'-carboethoxy-methyleneoxyphenyl)dipyrromethane with 5-formyl-1,1,3,3-tetramethylisoindolin-2-yloxyl (FTMIO) using the Lindsey method. The corresponding water-soluble spin-labeled porphyrins were also prepared. Subsequently, these compounds were characterized and their in vitro properties were evaluated. The electrochemical assay demonstrated that these isoindoline nitroxide-labeled porphyrins had similar electrochemical and redox properties to 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CTMIO). The electron paramagnetic resonance test showed that these porphyrins exhibited hyperfine splittings and characteristic spectra of CTMIO with typical nitroxide g-values and nitrogen isotropic hyperfine coupling constants. The in vitro cytotoxicity assay indicated that these porphyrins possessed low cytotoxicity to human renal tubular epithelial 293T cells (normal cells) and human hepatoma HepG2 cells (tumor cells). Fluorescence spectroscopy revealed that free base isoindoline nitroxide-labeled porphyrins exhibited fluorescence suppression characteristic of nitroxide-fluorophore systems. In vitro fluorescene imaging demonstrated that the reduced isoindoline nitroxide-labeled porphyrins eliminated fluorescence suppression and displayed strong red fluorescence imaging in HepG2 cells. Thus these isoindoline nitroxide-labeled porphyrins may be considered potentially as biological spin probes for fluorescence imaging and EPR spectroscopy.
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Affiliation(s)
- F Liu
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan 430074, China
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Kubota H, Komarov DA, Yasui H, Matsumoto S, Inanami O, Kirilyuk IA, Khramtsov VV, Hirata H. Feasibility of in vivo three-dimensional T 2* mapping using dicarboxy-PROXYL and CW-EPR-based single-point imaging. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2017; 30:291-298. [PMID: 28063096 DOI: 10.1007/s10334-016-0606-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 12/13/2016] [Accepted: 12/22/2016] [Indexed: 12/21/2022]
Abstract
OBJECTIVES The aim of this study was to demonstrate the feasibility of in vivo three-dimensional (3D) relaxation time T 2* mapping of a dicarboxy-PROXYL radical using continuous-wave electron paramagnetic resonance (CW-EPR) imaging. MATERIALS AND METHODS Isotopically substituted dicarboxy-PROXYL radicals, 3,4-dicarboxy-2,2,5,5-tetra(2H3)methylpyrrolidin-(3,4-2H2)-(1-15N)-1-oxyl (2H,15N-DCP) and 3,4-dicarboxy-2,2,5,5-tetra(2H3)methylpyrrolidin-(3,4-2H2)-1-oxyl (2H-DCP), were used in the study. A clonogenic cell survival assay was performed with the 2H-DCP radical using squamous cell carcinoma (SCC VII) cells. The time course of EPR signal intensities of intravenously injected 2H,15N-DCP and 2H-DCP radicals were determined in tumor-bearing hind legs of mice (C3H/HeJ, male, n = 5). CW-EPR-based single-point imaging (SPI) was performed for 3D T 2* mapping. RESULTS 2H-DCP radical did not exhibit cytotoxicity at concentrations below 10 mM. The in vivo half-life of 2H,15N-DCP in tumor tissues was 24.7 ± 2.9 min (mean ± standard deviation [SD], n = 5). The in vivo time course of the EPR signal intensity of the 2H,15N-DCP radical showed a plateau of 10.2 ± 1.2 min (mean ± SD) where the EPR signal intensity remained at more than 90% of the maximum intensity. During the plateau, in vivo 3D T 2* maps with 2H,15N-DCP were obtained from tumor-bearing hind legs, with a total acquisition time of 7.5 min. CONCLUSION EPR signals of 2H,15N-DCP persisted long enough after bolus intravenous injection to conduct in vivo 3D T 2* mapping with CW-EPR-based SPI.
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Affiliation(s)
- Harue Kubota
- Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, North 14, West 9, Kita-ku, Sapporo, 060-0814, Japan
| | - Denis A Komarov
- Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, North 14, West 9, Kita-ku, Sapporo, 060-0814, Japan
| | - Hironobu Yasui
- Central Institute of Isotope Science, Hokkaido University, North 15, West 7, Kita-ku, Sapporo, 060-0815, Japan
| | - Shingo Matsumoto
- Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, North 14, West 9, Kita-ku, Sapporo, 060-0814, Japan
| | - Osamu Inanami
- Laboratory of Radiation Biology, Graduate School of Veterinary Medicine, Hokkaido University, North 18, West 9, Kita-ku, Sapporo, 060-0818, Japan
| | - Igor A Kirilyuk
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, 9, Ac. Lavrentieva Ave., Novosibirsk, 630090, Russia
| | - Valery V Khramtsov
- Department of Biochemistry, West Virginia University, Robert C. Byrd Health Sciences Center, 1 Medical Center Drive, Morgantown, WV, 26506, USA
| | - Hiroshi Hirata
- Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, North 14, West 9, Kita-ku, Sapporo, 060-0814, Japan.
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10
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Legenzov EA, Muralidharan S, Woodcock LB, Eaton GR, Eaton SS, Rosen GM, Kao JPY. Designing Molecular Probes To Prolong Intracellular Retention: Application to Nitroxide Spin Probes. Bioconjug Chem 2016; 27:2923-2930. [PMID: 27998079 DOI: 10.1021/acs.bioconjchem.6b00595] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Targeted delivery of molecular probes into cells enables cellular imaging through optical and magnetic modalities. Probe molecules that are well retained by cells can accumulate to higher intracellular concentrations, and thus increase the signal-to-noise ratio of, and widen the temporal window for, imaging. Here we synthesize a paramagnetic spin probe bearing six ionic functional groups and show that it has long intracellular half-life (>12 h) and exceptional biostability in living cells. We demonstrate that judicious incorporation of ionic substituents on probe molecules systematically increases intracellular retention time, and should therefore be beneficial to imaging experiments.
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Affiliation(s)
- Eric A Legenzov
- Center for Biomedical Engineering & Technology, and Department of Physiology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
| | - Sukumaran Muralidharan
- Center for Biomedical Engineering & Technology, and Department of Physiology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
| | - Lukas B Woodcock
- Department of Chemistry and Biochemistry, University of Denver , Denver, Colorado 80208, United States
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver , Denver, Colorado 80208, United States
| | - Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver , Denver, Colorado 80208, United States
| | - Gerald M Rosen
- Department of Pharmaceutical Sciences, School of Pharmacy, and Center for Biomedical Engineering & Technology, School of Medicine, University of Maryland , Baltimore, Maryland 21201, United States
| | - Joseph P Y Kao
- Center for Biomedical Engineering & Technology, and Department of Physiology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
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11
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Weaver J, Burks SR, Liu KJ, Kao JPY, Rosen GM. In vivo EPR oximetry using an isotopically-substituted nitroxide: Potential for quantitative measurement of tissue oxygen. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 271:68-74. [PMID: 27567323 PMCID: PMC5266518 DOI: 10.1016/j.jmr.2016.08.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 08/12/2016] [Accepted: 08/15/2016] [Indexed: 06/06/2023]
Abstract
Variations in brain oxygen (O2) concentration can have profound effects on brain physiology. Thus, the ability to quantitate local O2 concentrations noninvasively in vivo could significantly enhance understanding of several brain pathologies. However, quantitative O2 mapping in the brain has proven difficult. The electron paramagnetic resonance (EPR) spectra of nitroxides are sensitive to molecular O2 and can be used to estimate O2 concentrations in aqueous media. We recently synthesized labile-ester-containing nitroxides, such as 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 4), which accumulate in cerebral tissue after in situ hydrolysis, and thus enable spatial mapping of O2 concentrations in the mouse brain by EPR imaging. In an effort to improve O2 quantitation, we prepared 3-acetoxymethoxycarbonyl-2,2,5,5-tetra((2)H3)methyl-1-(3,4,4-(2)H3,1-(15)N)pyrrolidinyloxyl (nitroxide 2), which proved to be a more sensitive probe than its normo-isotopic version for quantifying O2 in aqueous solutions of various O2 concentrations. We now demonstrate that this isotopically substituted nitroxide is ∼2-fold more sensitive in vivo than the normo-isotopic nitroxide 4. Moreover, in vitro and in vivo EPR spectral-spatial imaging results with nitroxide 2 demonstrate significant improvement in resolution, reconstruction and spectral response to local O2 concentrations in cerebral tissue. Thus, isotopic-substituted nitroxides, such as 2, are excellent sensors for in vivo O2 quantitation in tissues, such as the brain.
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Affiliation(s)
- John Weaver
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, United States; Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico, Albuquerque, NM 87131, United States.
| | - Scott R Burks
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, MD 21201, United States
| | - Ke Jian Liu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, United States; Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico, Albuquerque, NM 87131, United States
| | - Joseph P Y Kao
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, MD 21201, United States
| | - Gerald M Rosen
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, MD 21201, United States; Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, United States
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12
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Biller JR, Mitchell DG, Tseytlin M, Elajaili H, Rinard GA, Quine RW, Eaton SS, Eaton GR. Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo. J Vis Exp 2016. [PMID: 27768025 DOI: 10.3791/54068] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We demonstrate a superior method of 2D spectral-spatial imaging of stable radical reporter molecules at 250 MHz using rapid-scan electron-paramagnetic-resonance (RS-EPR), which can provide quantitative information under in vivo conditions on oxygen concentration, pH, redox status and concentration of signaling molecules (i.e., OH•, NO•). The RS-EPR technique has a higher sensitivity, improved spatial resolution (1 mm), and shorter acquisition time in comparison to the standard continuous wave (CW) technique. A variety of phantom configurations have been tested, with spatial resolution varying from 1 to 6 mm, and spectral width of the reporter molecules ranging from 16 µT (160 mG) to 5 mT (50 G). A cross-loop bimodal resonator decouples excitation and detection, reducing the noise, while the rapid scan effect allows more power to be input to the spin system before saturation, increasing the EPR signal. This leads to a substantially higher signal-to-noise ratio than in conventional CW EPR experiments.
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Affiliation(s)
- Joshua R Biller
- Department of Chemistry and Biochemistry, University of Denver; Magnetic Imaging Group, Applied Physics Division, Physical Measurements Laboratory, National Institute of Standards and Technology
| | | | - Mark Tseytlin
- Department of Radiology, Geisel School of Medicine, Dartmouth University; Department of Biochemistry, West Virginia University
| | - Hanan Elajaili
- Department of Chemistry and Biochemistry, University of Denver
| | - George A Rinard
- Department of Electrical and Computer Engineering, University of Denver
| | | | - Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver;
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13
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Legenzov EA, Sims SJ, Dirda NDA, Rosen GM, Kao JPY. Disulfide-Linked Dinitroxides for Monitoring Cellular Thiol Redox Status through Electron Paramagnetic Resonance Spectroscopy. Biochemistry 2015; 54:6973-82. [PMID: 26523485 DOI: 10.1021/acs.biochem.5b00531] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Intracellular thiol-disulfide redox balance is crucial to cell health, and may be a key determinant of a cancer's response to chemotherapy and radiation therapy. The ability to assess intracellular thiol-disulfide balance may thus be useful not only in predicting responsiveness of cancers to therapy, but in assessing predisposition to disease. Assays of thiols in biology have relied on colorimetry or fluorimetry, both of which require UV-visible photons, which do not penetrate the body. Low-frequency electron paramagnetic resonance imaging (EPRI) is an emerging magnetic imaging technique that uses radio waves, which penetrate the body well. Therefore, in combination with tailored imaging agents, EPRI affords the opportunity to image physiology within the body. In this study, we have prepared water-soluble and membrane-permeant disulfide-linked dinitroxides, at natural isotopic abundance, and with D,(15)N-substitution. Thiols such as glutathione cleave the disulfides, with simple bimolecular kinetics, to yield the monomeric nitroxide species, with distinctive changes in the EPR spectrum. Using the D,(15)N-substituted disulfide-dinitroxide and EPR spectroscopy, we have obtained quantitative estimates of accessible intracellular thiol in cultured human lymphocytes. Our estimates are in good agreement with published measurements. This suggests that in vivo EPRI of thiol-disulfide balance is feasible. Finally, we discuss the constraints on the design of probe molecules that would be useful for in vivo EPRI of thiol redox status.
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Affiliation(s)
- Eric A Legenzov
- Center for Biomedical Engineering & Technology, and Department of Physiology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
| | - Stephen J Sims
- Center for Biomedical Engineering & Technology, and Department of Physiology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
| | - Nathaniel D A Dirda
- Center for Biomedical Engineering & Technology, and Department of Physiology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
| | - Gerald M Rosen
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy , Baltimore, Maryland 21201, United States
| | - Joseph P Y Kao
- Center for Biomedical Engineering & Technology, and Department of Physiology, University of Maryland School of Medicine , Baltimore, Maryland 21201, United States
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14
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Gorodetsky AA, Kirilyuk IA, Khramtsov VV, Komarov DA. Functional electron paramagnetic resonance imaging of ischemic rat heart: Monitoring of tissue oxygenation and pH. Magn Reson Med 2015; 76:350-8. [PMID: 26301868 DOI: 10.1002/mrm.25867] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 06/29/2015] [Accepted: 07/13/2015] [Indexed: 12/14/2022]
Abstract
PURPOSE Electron paramagnetic resonance (EPR) imaging in the spectral-spatial domain with application of soluble paramagnetic probes provides an opportunity for spatially resolved functional measurements of living objects. The purpose of this study was to develop EPR methods for visualization of oxygenation and acidosis of ischemic myocardium. METHODS EPR oxygen measurements were performed using isotopically substituted (2) H,(15) N-dicarboxyproxyl. The radical has an EPR line width of 320 mG and oxygen-induced line broadening of 0.53 mG/mm Hg, providing oxygen sensitivity down to 5 μM. pH measurements were performed using previously developed pH-sensitive imidazoline nitroxide. The radical has an EPR spectrum with pH-dependable hyperfine splitting, pK = 6.6, providing pH sensitivity of approximately 0.05 U in the physiological range. RESULTS EPR imaging of isolated and perfused rat hearts was performed in the two-dimensional + spectral domain. The spatial resolution of the measurements was about 1.4 mm. Marked tissue hypoxia was observed in the ischemic area of the heart after occlusion of the left anterior descending coronary artery. Tissue oxygenation was partly restored upon reperfusion. EPR mapping of myocardial pH indicated acidosis of the ischemic area down to pH 6.7-6.8. CONCLUSION This study demonstrates the capability of low-field EPR and the nitroxide spin probes for mapping of myocardial oxygenation and pH. The developed approaches might be used for noninvasive investigation of microenvironment on living objects. Magn Reson Med 76:350-358, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Artem A Gorodetsky
- Vorozhtsov Institute of Organic Chemistry, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
| | - Igor A Kirilyuk
- Vorozhtsov Institute of Organic Chemistry, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
| | - Valery V Khramtsov
- Heart & Lung Research Institute, Ohio State University, Columbus, Ohio, USA.,Department of Biochemistry, School of Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Denis A Komarov
- Vorozhtsov Institute of Organic Chemistry, Novosibirsk, Russia.,Meshalkin State Research Institute of Circulation Pathology, Novosibirsk, Russia
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15
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Frank J, Elewa M, Said MM, El Shihawy HA, El-Sadek M, Müller D, Meister A, Hause G, Drescher S, Metz H, Imming P, Mäder K. Synthesis, Characterization, and Nanoencapsulation of Tetrathiatriarylmethyl and Tetrachlorotriarylmethyl (Trityl) Radical Derivatives—A Study To Advance Their Applicability as in Vivo EPR Oxygen Sensors. J Org Chem 2015; 80:6754-66. [PMID: 26020133 DOI: 10.1021/acs.joc.5b00918] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Tissue oxygenation plays an important role in the pathophysiology of various diseases and is often a marker of prognosis and therapeutic response. EPR (ESR) is a suitable noninvasive oximetry technique. However, to reliably deploy soluble EPR probes as oxygen sensors in complex biological systems, there is still a need to investigate and improve their specificity, sensitivity, and stability. We reproducibly synthesized various derivatives of tetrathiatriarylmethyl and tetrachlorotriarylmethyl (trityl) radicals. Hydrophilic radicals were investigated in aqueous solution mimicking physiological conditions by, e.g., variation of viscosity and ionic strength. Their specificity was satisfactory, but the oxygen sensitivity was low. To enhance the capability of trityl radicals as oxygen sensors, encapsulation into oily core nanocapsules was performed. Thus, different lipophilic triesters were prepared and characterized in oily solution employing oils typically used in drug formulations, i.e., middle-chain triglycerides and isopropyl myristate. Our screening identified the deuterated ethyl ester of D-TAM (radical 13) to be suitable. It had an extremely narrow single EPR line under anoxic conditions and excellent oxygen sensitivity. After encapsulation, it retained its oxygen responsiveness and was protected against reduction by ascorbic acid. These biocompatible and highly sensitive nanosensors offer great potential for future EPR oximetry applications in preclinical research.
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Affiliation(s)
- Juliane Frank
- †Institut für Pharmazie, Martin-Luther-Universität (MLU) Halle-Wittenberg, Wolfgang-Langenbeck-Strasse 4, 06120 Halle (Saale), Germany
| | - Marwa Elewa
- †Institut für Pharmazie, Martin-Luther-Universität (MLU) Halle-Wittenberg, Wolfgang-Langenbeck-Strasse 4, 06120 Halle (Saale), Germany.,‡Faculty of Pharmacy, Suez Canal University, P.O. 41522, Ismailia, Egypt
| | - Mohamed M Said
- ‡Faculty of Pharmacy, Suez Canal University, P.O. 41522, Ismailia, Egypt
| | - Hosam A El Shihawy
- ‡Faculty of Pharmacy, Suez Canal University, P.O. 41522, Ismailia, Egypt
| | | | - Diana Müller
- †Institut für Pharmazie, Martin-Luther-Universität (MLU) Halle-Wittenberg, Wolfgang-Langenbeck-Strasse 4, 06120 Halle (Saale), Germany
| | - Annette Meister
- ⊥Center for Structure and Dynamics of Proteins (MZP), Biocenter Martin-Luther-Universität (MLU) Halle-Wittenberg, Weinbergweg 22, 06120 Halle (Saale), Germany
| | - Gerd Hause
- #Biocenter Martin-Luther-Universität (MLU) Halle-Wittenberg, Weinbergweg 22, 06120 Halle (Saale), Germany
| | - Simon Drescher
- †Institut für Pharmazie, Martin-Luther-Universität (MLU) Halle-Wittenberg, Wolfgang-Langenbeck-Strasse 4, 06120 Halle (Saale), Germany
| | - Hendrik Metz
- †Institut für Pharmazie, Martin-Luther-Universität (MLU) Halle-Wittenberg, Wolfgang-Langenbeck-Strasse 4, 06120 Halle (Saale), Germany
| | - Peter Imming
- †Institut für Pharmazie, Martin-Luther-Universität (MLU) Halle-Wittenberg, Wolfgang-Langenbeck-Strasse 4, 06120 Halle (Saale), Germany
| | - Karsten Mäder
- †Institut für Pharmazie, Martin-Luther-Universität (MLU) Halle-Wittenberg, Wolfgang-Langenbeck-Strasse 4, 06120 Halle (Saale), Germany
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16
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Shundrin LA, Kirilyuk IA, Grigor’ev IA. 3-Carboxy-2,2,5,5-tetra(2H3)methyl-[4-2H(1H)]-3-pyrroline-(1-15N)-1-oxyl as a spin probe for in vivo L-band electron paramagnetic resonance imaging. MENDELEEV COMMUNICATIONS 2014. [DOI: 10.1016/j.mencom.2014.09.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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17
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Tseitlin M, Biller JR, Elajaili H, Khramtsov VV, Dhimitruka I, Eaton GR, Eaton SS. New spectral-spatial imaging algorithm for full EPR spectra of multiline nitroxides and pH sensitive trityl radicals. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 245:150-5. [PMID: 25058914 PMCID: PMC4134677 DOI: 10.1016/j.jmr.2014.05.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 05/28/2014] [Accepted: 05/30/2014] [Indexed: 05/13/2023]
Abstract
An algorithm is derived and demonstrated that reconstructs an EPR spectral-spatial image from projections with arbitrarily selected gradients. This approach permits imaging wide spectra without the use of the very large sweep widths and gradients that would be required for spectral-spatial imaging with filtered back projection reconstruction. Each projection is defined as the sum of contributions at the set of locations in the object. At each location gradients shift the spectra in the magnetic field domain, which is equivalent to a phase change in the Fourier-conjugate frequency domain. This permits solution of the problem in the frequency domain. The method was demonstrated for 2D images of phantoms consisting of (i) two tubes containing (14)N and (15)N nitroxide and (ii) two tubes containing a pH sensitive trityl radical at pH 7.0 and 7.2. In each case spectral slices through the image agree well with the full spectra obtained in the absence of gradient.
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Affiliation(s)
- Mark Tseitlin
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80210, USA
| | - Joshua R Biller
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80210, USA
| | - Hanan Elajaili
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80210, USA
| | - Valery V Khramtsov
- Dorothy M. Davis Heart & Lung Research Institute and Division of Pulmonary, Allergy, Critical Care & Sleep Medicine, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Ilirian Dhimitruka
- Dorothy M. Davis Heart & Lung Research Institute and Division of Pulmonary, Allergy, Critical Care & Sleep Medicine, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80210, USA.
| | - Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80210, USA
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18
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Biller JR, Tseitlin M, Quine RW, Rinard GA, Weismiller HA, Elajaili H, Rosen GM, Kao JPY, Eaton SS, Eaton GR. Imaging of nitroxides at 250MHz using rapid-scan electron paramagnetic resonance. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 242:162-8. [PMID: 24650729 PMCID: PMC4081024 DOI: 10.1016/j.jmr.2014.02.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 02/15/2014] [Accepted: 02/18/2014] [Indexed: 05/12/2023]
Abstract
Projections for 2D spectral-spatial images were obtained by continuous wave and rapid-scan electron paramagnetic resonance using a bimodal cross-loop resonator at 251MHz. The phantom consisted of three 4mm tubes containing different (15)N,(2)H-substituted nitroxides. Rapid-scan and continuous wave images were obtained with 5min total acquisition times. For comparison, images also were obtained with 29s acquisition time for rapid scan and 15min for continuous wave. Relative to continuous wave projections obtained for the same data acquisition time, rapid-scan projections had significantly less low-frequency noise and substantially higher signal-to-noise at higher gradients. Because of the improved image quality for the same data acquisition time, linewidths could be determined more accurately from the rapid-scan images than from the continuous wave images.
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Affiliation(s)
- Joshua R Biller
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States; Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208, United States
| | - Mark Tseitlin
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States; Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208, United States
| | - Richard W Quine
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208, United States; School of Engineering and Computer Science, University of Denver, Denver, CO 80208, United States
| | - George A Rinard
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208, United States; School of Engineering and Computer Science, University of Denver, Denver, CO 80208, United States
| | - Hilary A Weismiller
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States; Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208, United States
| | - Hanan Elajaili
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States; Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208, United States
| | - Gerald M Rosen
- Center for Biomedical Engineering and Technology, University of Maryland, School of Medicine, Baltimore, MD 21201, United States; Department of Pharmaceutical Sciences, University of Maryland, Baltimore, MD 21201, United States
| | - Joseph P Y Kao
- Center for Biomedical Engineering and Technology, University of Maryland, School of Medicine, Baltimore, MD 21201, United States; Department of Physiology, University of Maryland, School of Medicine, Baltimore, MD 21201, United States
| | - Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States; Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208, United States
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States; Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208, United States.
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Biller JR, Elajaili H, Meyer V, Rosen GM, Eaton SS, Eaton GR. Electron spin-lattice relaxation mechanisms of rapidly-tumbling nitroxide radicals. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 236:47-56. [PMID: 24056272 PMCID: PMC3952064 DOI: 10.1016/j.jmr.2013.08.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2012] [Revised: 08/13/2013] [Accepted: 08/14/2013] [Indexed: 05/12/2023]
Abstract
Electron spin relaxation times at 295 K were measured at frequencies between 250 MHz and 34 GHz for perdeuterated 2,2,6,6-tetramethyl-4-piperidone-1-oxyl (PDT) in five solvents with viscosities that result in tumbling correlation times, τR, between 4 and 50 ps and for three (14)N/(15)N pairs of nitroxides in water with τR between 9 and 19 ps. To test the impact of structure on relaxation three additional nitroxides with τR between 10 and 26 ps were studied. In this fast tumbling regime T2(-1)~T1(-1) at frequencies up to about 9 GHz. At 34 GHz T2(-1)>T1(-1) due to increased contributions to T2(-1) from incomplete motional averaging of g-anisotropy, and T2(-1)-T1(-1) is proportional to τR. The contribution to T1(-1) from spin rotation is independent of frequency and decreases as τR increases. Spin rotation dominates T1(-1) at 34 GHz for all τR studied, and at all frequencies studied for τR=4 ps. The contribution to T1(-1) from modulation of nitrogen hyperfine anisotropy increases as frequency decreases and as τR increases; it dominates at low frequencies for τR>~15 ps. The contribution from modulation of g anisotropy is significant only at 34 GHz. Inclusion of a thermally-activated process was required to account for the observation that for most of the radicals, T1(-1) was smaller at 250 MHz than at 1-2 GHz. The significant (15)N/(14)N isotope effect, the small H/D isotope effect, and the viscosity dependence of the magnitude of the contribution from the thermally-activated process suggest that it arises from intramolecular motions of the nitroxide ring that modulate the isotropic A values.
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Affiliation(s)
- Joshua R. Biller
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80208
| | - Hanan Elajaili
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80208
| | - Virginia Meyer
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80208
| | - Gerald M. Rosen
- Department of Pharmaceutical Sciences, Center for EPR Imaging in Vivo Physiology, and Center for Biomedical Engineering and Technology, University of Maryland, Baltimore, MD 21201
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80208
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry and Center for EPR Imaging In Vivo Physiology, University of Denver, Denver, CO 80208
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20
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Decroos C, Balland V, Boucher JL, Bertho G, Xu-Li Y, Mansuy D. Toward stable electron paramagnetic resonance oximetry probes: synthesis, characterization, and metabolic evaluation of new ester derivatives of a tris-(para-carboxyltetrathiaaryl)methyl (TAM) radical. Chem Res Toxicol 2013; 26:1561-9. [PMID: 24010758 DOI: 10.1021/tx400250a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Tris(p-carboxyltetrathiaaryl)methyl (TAM) radicals, such as 1a ("Finland" radical), are useful EPR probes for oximetry. However, they are rapidly metabolized by liver microsomes in the presence of NADPH, with the formation of diamagnetic quinone-methide metabolites resulting from an oxidative decarboxylation of one of their carboxylate substituents. In an effort to obtain TAM derivatives potentially more metabolically stable in vivo, we have synthesized four new TAM radicals in which the carboxylate substituents of 1a have been replaced with esters groups bearing various alkyl chains designed to render them water-soluble. The new compounds were completely characterized by UV-vis and EPR spectroscopies, high resolution mass spectrometry (HRMS), and electrochemistry. Two of them were water-soluble enough to undergo detailed microsomal metabolic studies in comparison with 1a. They were found to be stable in the presence of the esterases present in rat liver microsomes and cytosol, and, contrary to 1a, stable to oxidation in the presence of NADPH-supplemented microsomes. A careful study of their possible microsomal reduction under anaerobic or aerobic conditions showed that they were more easily reduced than 1a, in agreement with their higher reduction potentials. They were reduced into the corresponding anions not only under anaerobic conditions but also in the presence of dioxygen. These anions were much more stable than that of 1a and could be characterized by UV-vis spectroscopy, MS, and at the level of their protonated product. However, they were oxidized by O₂, giving back to the starting ester radicals and catalyzing a futile cycle of O₂ reduction. Such reactions should be considered in the design of future stable EPR probes for oximetry in vivo.
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Affiliation(s)
- Christophe Decroos
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris Descartes, Sorbonne Paris Cité, 45 rue des Saints-Pères, 75270 Paris, France
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21
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Redler G, Barth ED, Bauer KS, Kao JPY, Rosen GM, Halpern HJ. In vivo electron paramagnetic resonance imaging of differential tumor targeting using cis-3,4-di(acetoxymethoxycarbonyl)-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl. Magn Reson Med 2013; 71:1650-6. [PMID: 23776127 DOI: 10.1002/mrm.24813] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 03/27/2013] [Accepted: 04/26/2013] [Indexed: 12/21/2022]
Abstract
PURPOSE Electron paramagnetic resonance spectroscopy promises quantitative images of important physiologic markers of animal tumors and normal tissues, such as pO(2), pH, and thiol redox status. These parameters of tissue function are conveniently reported by tailored nitroxides. For defining tumor physiology, it is vital that nitroxides are selectively localized in tumors relative to normal tissue. Furthermore, these paramagnetic species should be specifically taken up by cells of the tumor, thereby reporting on both the site of tumor formation and the physiological status of the tissue. This study investigates the tumor localization of the novel nitroxide, cis-3,4-di(acetoxymethoxycarbonyl)-2,2,5,5-tetramethyl-1-pyrrolidin-yloxyl 3 relative to the corresponding di-acid 4. METHODS We obtained images of nitroxide 3 infused intravenously into C3H mice bearing 0.5-cm(3) FSa fibrosarcoma on the leg, and compared these with images of similar tumors infused with nitroxide 4. RESULTS The ratio of spectral intensity from within the tumor-bearing region to that of normal tissue was higher in the mice injected with 3 relative to 4. CONCLUSION This establishes the possibility of tumor imaging with a nitroxide with intracellular distribution and provides the basis for EPR images of animal models to investigate the relationship between crucial aspects of tumor microenvironment and malignancy and its response to therapy.
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Affiliation(s)
- Gage Redler
- Department of Radiation and Cellular Oncology, University of Chicago, Chicago, Illinois, USA; Center for EPR Imaging In Vivo Physiology, University of Chicago, Chicago, Illinois, USA
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22
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Epel, B, Halpern H. Electron paramagnetic resonance oxygen imaging in vivo. ELECTRON PARAMAGNETIC RESONANCE 2012. [DOI: 10.1039/9781849734837-00180] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
This review covers the last 15 years of the development of EPR in vivo oxygen imaging. During this time, a number of major technological and methodological advances have taken place. Narrow line width, long relaxation time, and non-toxic triaryl methyl radicals were introduced in the late 1990s. These not only improved continuous wave (CW) imaging, but also enabled the application of pulse EPR imaging to animals. Recent developments in pulse technology have brought an order of magnitude increase in image acquisition speed, enhancement of sensitivity, and considerable improvement in the precision and accuracy of oxygen measurements. Consequently, pulse methods take up a significant part of this review.
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Affiliation(s)
- Boris Epel,
- Center for EPR Imaging in vivo Physiology the University of Chicago, Department of Radiation and Cellular Oncology (MC 1105), Chicago Illinois 60637
| | - Howard Halpern
- Center for EPR Imaging in vivo Physiology the University of Chicago, Department of Radiation and Cellular Oncology (MC 1105), Chicago Illinois 60637
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Yan GP, Liu F, Ai CW, Zou TJ, Li L, Guo QZ, Yu XH, Li Q. Polyaspartamide spin probes containing isoindoline nitroxide and porphyrin groups. J BIOACT COMPAT POL 2012. [DOI: 10.1177/0883911512445606] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Water-soluble polyaspartamide isoindoline nitroxides 5-(4′-aminophenyl)-10,15,20-tris (4′-sulfonatophenyl) porphyrin, trisodium salt–poly[α,β- N-(2-hydroxyethyl)-l-aspartamide]–5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl were synthesized by the incorporation of 5-(4′-aminophenyl)-10,15,20-tris(4′-sulfonatophenyl) porphyrin, trisodium salt, as a tumor-targeting group, and 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl into poly[α,β- N-(2-hydroxyethyl)-l-aspartamide]. These compounds were characterized, and the in vitro properties were evaluated. The polyaspartamide isoindoline nitroxides had higher relaxation effectiveness and had greater toxicity to HeLa cells than that of 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl. The polyaspartamide isoindoline nitroxides retained similar electrochemical properties and redox reaction mechanisms as the parent nitroxides. The electron paramagnetic resonance spectra of polyaspartamide isoindoline nitroxides exhibited characteristic hyperfine electron paramagnetic resonance spectra of tetramethyl isoindoline nitroxides, with typical nitroxide g-values and nitrogen isotropic hyperfine coupling constants. Therefore, the water-soluble 5-(4′-aminophenyl)-10,15,20-tris(4′-sulfonatophenyl) porphyrin, trisodium salt–poly[α,β- N-(2-hydroxyethyl)-l-aspartamide]–5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl is considered to be a novel potential spin probe for electron paramagnetic resonance.
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Affiliation(s)
- Guo-Ping Yan
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, China
| | - Fan Liu
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, China
| | - Chao-Wu Ai
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, China
| | - Tou-Jun Zou
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, China
| | - Liang Li
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, China
| | - Qing-Zhong Guo
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, China
| | - Xiang-Hua Yu
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, China
| | - Qian Li
- School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, China
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Biller JR, Meyer V, Elajaili H, Rosen GM, Kao JP, Eaton SS, Eatona GR. Relaxation times and line widths of isotopically-substituted nitroxides in aqueous solution at X-band. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 212:370-7. [PMID: 21843961 PMCID: PMC3196672 DOI: 10.1016/j.jmr.2011.07.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 07/21/2011] [Accepted: 07/22/2011] [Indexed: 05/16/2023]
Abstract
Optimization of nitroxides as probes for EPR imaging requires detailed understanding of spectral properties. Spin lattice relaxation times, spin packet line widths, nuclear hyperfine splitting, and overall lineshapes were characterized for six low molecular weight nitroxides in dilute deoxygenated aqueous solution at X-band. The nitroxides included 6-member, unsaturated 5-member, or saturated 5-member rings, most of which were isotopically labeled. The spectra are near the fast tumbling limit with T(1)∼T(2) in the range of 0.50-1.1 μs at ambient temperature. Both spin-lattice relaxation T(1) and spin-spin relaxation T(2) are longer for (15)N- than for (14)N-nitroxides. The dominant contributions to T(1) are modulation of nitrogen hyperfine anisotropy and spin rotation. Dependence of T(1) on nitrogen nuclear spin state m(I) was observed for both (14)N and (15)N. Unresolved hydrogen/deuterium hyperfine couplings dominate overall line widths. Lineshapes were simulated by including all nuclear hyperfine couplings and spin packet line widths that agreed with values obtained by electron spin echo. Line widths and relaxation times are predicted to be about the same at 250 MHz as at X-band.
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Affiliation(s)
- Joshua R. Biller
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208 and University of Maryland, Baltimore, Baltimore, MD, 21201
| | - Virginia Meyer
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208 and University of Maryland, Baltimore, Baltimore, MD, 21201
| | - Hanan Elajaili
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208 and University of Maryland, Baltimore, Baltimore, MD, 21201
| | - Gerald M. Rosen
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208 and University of Maryland, Baltimore, Baltimore, MD, 21201
- Center for Biomedical Engineering and Technology, University of Maryland, Baltimore, Baltimore, MD, 21201
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Baltimore, MD, 21201
| | - Joseph P.Y. Kao
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208 and University of Maryland, Baltimore, Baltimore, MD, 21201
- Center for Biomedical Engineering and Technology, University of Maryland, Baltimore, Baltimore, MD, 21201
- Department of Physiology, University of Maryland, Baltimore, Baltimore, MD, 21201
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208 and University of Maryland, Baltimore, Baltimore, MD, 21201
| | - Gareth R. Eatona
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
- Center for EPR Imaging in Vivo Physiology, University of Denver, Denver, CO 80208 and University of Maryland, Baltimore, Baltimore, MD, 21201
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Rajca A, Shiraishi K, Boratyński PJ, Pink M, Miyasaka M, Rajca S. Oxidation of Annelated Diarylamines: Analysis of Reaction Pathways to Nitroxide Diradical and Spirocyclic Products. J Org Chem 2011; 76:8447-57. [DOI: 10.1021/jo2017923] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Kouichi Shiraishi
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | | | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, United States
| | - Makoto Miyasaka
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
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Burks SR, Legenzov EA, Rosen GM, Kao JPY. Clearance and biodistribution of liposomally encapsulated nitroxides: a model for targeted delivery of electron paramagnetic resonance imaging probes to tumors. Drug Metab Dispos 2011; 39:1961-6. [PMID: 21737567 DOI: 10.1124/dmd.111.039636] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Electron paramagnetic resonance (EPR) imaging using nitroxides as molecular probes is potentially a powerful tool for the detection and physiological characterization of micrometastatic lesions. Encapsulating nitroxides in anti-HER2 immunoliposomes at high concentrations to take advantage of the "self-quenching" phenomenon of nitroxides allows generation of robust EPR signals in HER2-overexpressing breast tumor cells with minimal background from indifferent tissues or circulating liposomes. We investigated the in vivo pharmacological properties of nitroxides encapsulated in sterically stabilized liposomes designed for long circulation times. We show that circulation times of nitroxides can be extended from hours to days; this increases the proportion of liposomes in circulation to enhance tumor targeting. Furthermore, nitroxides encapsulated in sterically stabilized anti-HER2 immunoliposomes can be delivered to HER2-overexpressing tumors at micromolar concentrations, which should be imageable by EPR. Lastly, after in vivo administration, liposomally encapsulated nitroxide signal also appears in the liver, spleen, and kidneys. Although these organs are spatially distinct and would not hinder tumor imaging in our model, understanding nitroxide signal retention in these organs is essential for further improvements in EPR imaging contrast between tumors and other tissues. These results lay the foundation to use liposomally delivered nitroxides and EPR imaging to visualize tumor cells in vivo.
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Affiliation(s)
- Scott R Burks
- Center for Biomedical Engineering and Technology and Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, Maryland 21201, USA
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Quast H, Philipp G, Ross KH, Doht UM. Stable 3-Imino-2,3-dihydroindazol-1-yl Radicals. European J Org Chem 2011. [DOI: 10.1002/ejoc.201001659] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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