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D'Alonzo RA, Gill S, Rowshanfarzad P, Keam S, MacKinnon KM, Cook AM, Ebert MA. In vivo noninvasive preclinical tumor hypoxia imaging methods: a review. Int J Radiat Biol 2021; 97:593-631. [PMID: 33703994 DOI: 10.1080/09553002.2021.1900943] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Tumors exhibit areas of decreased oxygenation due to malformed blood vessels. This low oxygen concentration decreases the effectiveness of radiation therapy, and the resulting poor perfusion can prevent drugs from reaching areas of the tumor. Tumor hypoxia is associated with poorer prognosis and disease progression, and is therefore of interest to preclinical researchers. Although there are multiple different ways to measure tumor hypoxia and related factors, there is no standard for quantifying spatial and temporal tumor hypoxia distributions in preclinical research or in the clinic. This review compares imaging methods utilized for the purpose of assessing spatio-temporal patterns of hypoxia in the preclinical setting. Imaging methods provide varying levels of spatial and temporal resolution regarding different aspects of hypoxia, and with varying advantages and disadvantages. The choice of modality requires consideration of the specific experimental model, the nature of the required characterization and the availability of complementary modalities as well as immunohistochemistry.
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Affiliation(s)
- Rebecca A D'Alonzo
- School of Physics, Mathematics and Computing, The University of Western Australia, Crawley, Australia
| | - Suki Gill
- School of Physics, Mathematics and Computing, The University of Western Australia, Crawley, Australia.,Department of Radiation Oncology, Sir Charles Gairdner Hospital, Nedlands, Australia
| | - Pejman Rowshanfarzad
- School of Physics, Mathematics and Computing, The University of Western Australia, Crawley, Australia
| | - Synat Keam
- School of Medicine, The University of Western Australia, Crawley, Australia
| | - Kelly M MacKinnon
- School of Physics, Mathematics and Computing, The University of Western Australia, Crawley, Australia
| | - Alistair M Cook
- School of Medicine, The University of Western Australia, Crawley, Australia
| | - Martin A Ebert
- School of Physics, Mathematics and Computing, The University of Western Australia, Crawley, Australia.,Department of Radiation Oncology, Sir Charles Gairdner Hospital, Nedlands, Australia.,5D Clinics, Claremont, Australia
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2
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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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3
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Huang L, Yan C, Cui D, Yan Y, Liu X, Lu X, Tan X, Lu X, Xu J, Xu Y, Liu R. Organic Radical Contrast Agents Based on Polyacetylenes Containing 2,2,6,6-Tetramethylpiperidine 1-Oxyl (TEMPO): Targeted Magnetic Resonance (MR)/Optical Bimodal Imaging of Folate Receptor Expressing HeLa Tumors in Vitro and in Vivoa. Macromol Biosci 2015; 15:788-98. [PMID: 25677802 DOI: 10.1002/mabi.201400403] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 01/23/2015] [Indexed: 12/25/2022]
Affiliation(s)
- Lixia Huang
- Department of Medical Imaging Center, Nanfang Hospital; Southern Medical University; Guangzhou 510515 China
- Department of Radiology; Guangdong Provincial Traditional Chinese Medical Hospital; Guangzhou 510120 China
| | - Chenggong Yan
- Department of Medical Imaging Center, Nanfang Hospital; Southern Medical University; Guangzhou 510515 China
| | - Danting Cui
- Department of Medical Imaging Center, Nanfang Hospital; Southern Medical University; Guangzhou 510515 China
| | - Yichen Yan
- School of Pharmaceutical Sciences; Southern Medical University; Guangzhou 510515 China
| | - Xiang Liu
- Department of Medical Imaging Center, Nanfang Hospital; Southern Medical University; Guangzhou 510515 China
| | - Xinwei Lu
- School of Pharmaceutical Sciences; Southern Medical University; Guangzhou 510515 China
| | - Xiangliang Tan
- Department of Medical Imaging Center, Nanfang Hospital; Southern Medical University; Guangzhou 510515 China
| | - Xiaodan Lu
- Department of Medical Imaging Center, Nanfang Hospital; Southern Medical University; Guangzhou 510515 China
| | - Jun Xu
- Department of Hematology, Nanfang Hospital; Southern Medical University; Guangzhou 510515 China
| | - Yikai Xu
- Department of Medical Imaging Center, Nanfang Hospital; Southern Medical University; Guangzhou 510515 China
| | - Ruiyuan Liu
- School of Pharmaceutical Sciences; Southern Medical University; Guangzhou 510515 China
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4
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Danhier P, Gallez B. Electron paramagnetic resonance: a powerful tool to support magnetic resonance imaging research. CONTRAST MEDIA & MOLECULAR IMAGING 2014; 10:266-81. [PMID: 25362845 DOI: 10.1002/cmmi.1630] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 09/18/2014] [Indexed: 12/31/2022]
Abstract
The purpose of this paper is to describe some of the areas where electron paramagnetic resonance (EPR) has provided unique information to MRI developments. The field of application mainly encompasses the EPR characterization of MRI paramagnetic contrast agents (gadolinium and manganese chelates, nitroxides) and superparamagnetic agents (iron oxide particles). The combined use of MRI and EPR has also been used to qualify or disqualify sources of contrast in MRI. Illustrative examples are presented with attempts to qualify oxygen sensitive contrast (i.e. T1 - and T2 *-based methods), redox status or melanin content in tissues. Other areas are likely to benefit from the combined EPR/MRI approach, namely cell tracking studies. Finally, the combination of EPR and MRI studies on the same models provides invaluable data regarding tissue oxygenation, hemodynamics and energetics. Our description will be illustrative rather than exhaustive to give to the readers a flavour of 'what EPR can do for MRI'.
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Affiliation(s)
- Pierre Danhier
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium
| | - Bernard Gallez
- Biomedical Magnetic Resonance Research Group, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium
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Wang X, Emoto M, Sugimoto A, Miyake Y, Itto K, Amasaka M, Xu S, Hirata H, Fujii H, Arimoto H. Synthesis of 15N-labeled 4-oxo-2,2,6,6-tetraethylpiperidine nitroxide for EPR brain imaging. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2014.02.063] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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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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7
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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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8
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Kleschyov AL, Sen' V, Golubev V, Münnemann K, Hinderberger D, Lackner KJ, Weber S, Terekhov M, Schreiber LM, Münzel T. Heparin-polynitroxides: synthesis and preliminary evaluation as cardiovascular EPR/MR imaging probes and extracellular space-targeted antioxidants. Eur J Med Chem 2012; 58:265-71. [PMID: 23127990 DOI: 10.1016/j.ejmech.2012.09.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Revised: 07/11/2012] [Accepted: 09/24/2012] [Indexed: 10/27/2022]
Abstract
We report here the synthesis of heparin-polynitroxide derivatives (HPNs) in which nitroxide moieties are linked either to uronic acid or glycosamine residues of the heparin macromolecule. HPNs have low anticoagulant activity, possess superoxide scavenging properties, bind to the vascular endothelium/extra-cellular matrix and can be detected by EPR and MRI techniques. As the vascular wall-targeted redox-active paramagnetic compounds, HPNs may have both diagnostic (molecular MRI) and therapeutic (ecSOD mimics) applications.
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Affiliation(s)
- Andrei L Kleschyov
- Second Medical Department, University Medical Center, Johannes Gutenberg University, Mainz 55131, Germany.
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9
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Tomizawa A, Hadjidekov G, Ishii I, Bakalova R, Zhelev Z, Aoki I, Saga T, Kitada M. Nitroxide derivatives for imaging of hypercholesterolemia-induced kidney dysfunction and assessing the effectiveness of antilipidemic drugs. Mol Pharm 2011; 8:1962-9. [PMID: 21744874 DOI: 10.1021/mp200087v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The present study was designed to clarify the possibility for application of nitroxide derivatives in magnetic resonance imaging (MRI) of hypercholesterolemia-mediated renal dysfunction in mice, as well as to assess the effectiveness of antilipidemic drugs (cholestyramine and ezetimibe). The mice were separated in four groups: (i) on a normal diet (ND) without medication (control); (ii) on a high cholesterol diet (CD) without medication; (iii) CD mice receiving cholestyramine; and (iv) CD mice receiving ezetimibe. In CD mice without medication, a hypercholesterolemia was developed, detected by the increasing of total plasma cholesterol and non-HDL cholesterol, and decreasing of HDL cholesterol. The hypercholesterolemia compromised renal function: blood urea nitrogen, creatine and uric acid increased significantly, accompanied with development of glomerulosclerosis, enhancement of the amount of neutrophils and overexpression of metalloproteinase-9. The mice were subjected to anesthesia and MR imaging was performed on 7 T magnet (T1-weighted incoherent gradient-echo sequence; fast low-angle shot). The region-of-interest was selected within the kidney. The images were obtained before and after injection of contrast probe [carbamoyl-PROXYL (CMP) or Gd-DTPA]. In the kidney of ND mice, the MRI signal intensity increased after injection of CMP, reached a maximum (very well-defined renal filtration peak) and decreased to the baseline level within 14 min. In kidney of CD mice, the CMP-mediated enhancement of MRI signal was not detected. Antilipidemic drugs patially abolished the effect of hypercholesterolemia on CMP-enhanced MRI in the kidney. The kinetic curves of Gd-enhanced MRI signal had also different profiles in the kidney of ND and CD mice. They were similar to the profiles of the kinetic curves, obtained from MR urography of healthy human and human with renal pathology, respectively. The present study suggests that CMP is a suitable MRI contrast probe for visualization of hypercholesterolemia-induced renal dysfunction in intact animals and the assessment of the efficacy of antilipidemic drugs. The probe was applied at a concentration that was 3 times lower than the LD50 for intravenous administration in mice. Since the probe is excreted by the kidney, it could be considered harmless for mammalians in the selected dose and appropriate candidate for translational research.
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Affiliation(s)
- Atsuyuki Tomizawa
- Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan
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10
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Khan N, Blinco JP, Bottle SE, Hosokawa K, Swartz HM, Micallef AS. The evaluation of new and isotopically labeled isoindoline nitroxides and an azaphenalene nitroxide for EPR oximetry. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 211:170-7. [PMID: 21665499 PMCID: PMC3143274 DOI: 10.1016/j.jmr.2011.05.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 05/14/2011] [Accepted: 05/14/2011] [Indexed: 05/26/2023]
Abstract
Isoindoline nitroxides are potentially useful probes for viable biological systems, exhibiting low cytotoxicity, moderate rates of biological reduction and favorable Electron Paramagnetic Resonance (EPR) characteristics. We have evaluated the anionic (5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl; CTMIO), cationic (5-(N,N,N-trimethylammonio)-1,1,3,3-tetramethylisoindolin-2-yloxyl iodide, QATMIO) and neutral (1,1,3,3-tetramethylisoindolin-2-yloxyl; TMIO) nitroxides and their isotopically labeled analogs ((2)H(12)- and/or (2)H(12)-(15)N-labeled) as potential EPR oximetry probes. An active ester analogue of CTMIO, designed to localize intracellularly, and the azaphenalene nitroxide 1,1,3,3-tetramethyl-2,3-dihydro-2-azaphenalen-2-yloxyl (TMAO) were also studied. While the EPR spectra of the unlabeled nitroxides exhibit high sensitivity to O(2) concentration, deuteration resulted in a loss of superhyperfine features and a subsequent reduction in O(2) sensitivity. Labeling the nitroxides with (15)N increased the signal intensity and this may be useful in decreasing the detection limits for in vivo measurements. The active ester nitroxide showed approximately 6% intracellular localization and low cytotoxicity. The EPR spectra of TMAO nitroxide indicated an increased rigidity in the nitroxide ring, due to dibenzo-annulation.
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Affiliation(s)
- Nadeem Khan
- EPR Centre for Viable Systems, Department of Radiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
| | - James P. Blinco
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Faculty of Science and Technology, Queensland University of Technology, Brisbane, Queensland 4001, Australia
| | - Steven E. Bottle
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Faculty of Science and Technology, Queensland University of Technology, Brisbane, Queensland 4001, Australia
| | - Kazuyuki Hosokawa
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Faculty of Science and Technology, Queensland University of Technology, Brisbane, Queensland 4001, Australia
| | - Harold M. Swartz
- EPR Centre for Viable Systems, Department of Radiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
| | - Aaron S. Micallef
- Australian Institute for Bioengineering and Nanotechnology and School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Queensland 4072, Australia
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Qiu X, Zhao H, Yu R, Zhang J, Lan M. Novel ferrocenyl nitroxide nanoparticles as electron paramagnetic resonance oximetry probes in vitro and in vivo. Nanomedicine (Lond) 2011; 6:225-31. [DOI: 10.2217/nnm.11.2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aims: In this article we report our recent developments in the field of electron paramagnetic resonance oximetry. Materials & methods: Novel synthesized ferrocenyl nitroxide radicals (FcN)-1–6 were evaluated to determine their electron paramagnetic resonance oxygen responsiveness and reduction resistance. The 3-ferrocenyl-N-(oxyl-2,2,6,6-tetramethylpiperidin-4-yl) butanamide radical (FcN-6), with outstanding electron paramagnetic resonance oxygen sensitivity, was encapsulated in Pluronic F-127 polymeric nanoparticles. Results: The nanoparticles exhibited good oxygen sensitivity, long-term stability of responsiveness, targeting to lung, liver and tumor, and low toxicity. Conclusion: These features make this novel nanoparticle especially valuable for mapping O2 concentrations in the body and monitoring the oxygen level inside tissues.
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Affiliation(s)
- Xiao Qiu
- Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis & Test, East China University of Science & Technology. Shanghai 200237, PR China
| | - Hongli Zhao
- Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis & Test, East China University of Science & Technology. Shanghai 200237, PR China
- The Institute of Applied Chemistry, East China University of Science & Technology, Shanghai, PR China
| | - Ronghua Yu
- Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis & Test, East China University of Science & Technology. Shanghai 200237, PR China
| | - Jiufeng Zhang
- Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis & Test, East China University of Science & Technology. Shanghai 200237, PR China
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Burks SR, Bakhshai J, Makowsky MA, Muralidharan S, Tsai P, Rosen GM, Kao JPY. (2)H,(15)N-substituted nitroxides as sensitive probes for electron paramagnetic resonance imaging. J Org Chem 2011; 75:6463-7. [PMID: 20828113 DOI: 10.1021/jo1011619] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electron paramagnetic resonance imaging (EPRI) using nitroxides is an emergent imaging method for studying in vivo physiology, including O(2) distribution in various tissues. Such imaging capabilities would allow O(2) mapping in tumors and in different brain regions following hypoxia or drug abuse. We have recently demonstrated that the anion of 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (2) can be entrapped in brain tissue to quantitate O(2) concentration in vivo. To increase the sensitivity of O(2) measurement by EPR imaging, we synthesized 3-carboxy-2,2,5,5-tetra((2)H(3))methyl-1-(3,4,4-(2)H(3),1-(15)N)pyrrolidinyloxyl (7). EPR spectroscopic measurements demonstrate that this fully isotopically substituted nitroxide markedly improves signal-to-noise ratio and, therefore, the sensitivity of EPR imaging. The new isotopically substituted nitroxide shows increased sensitivity to changes in O(2) concentration, which will enable more accurate O(2) measurement in tissues using EPRI.
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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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13
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Miyake M, Burks SR, Weaver J, Tsai P, Liu W, Bigio D, Bauer KS, Liu KJ, Rosen GM, Kao JPY. Comparison of two nitroxide labile esters for delivering electron paramagnetic resonance probes into mouse brain. J Pharm Sci 2010; 99:3594-600. [PMID: 20201101 DOI: 10.1002/jps.22102] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In vivo quantitation of O(2) in brain has been hindered by a lack of suitable imaging modalities. Development of low-frequency electron paramagnetic resonance (EPR) spectrometers that can detect free radicals in animals in real time makes it feasible to image paramagnetic oximetry probes such as nitroxides in brain tissue. We have shown that masking the carboxyl group of 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 1) as an esterase-labile acetoxymethyl ester yields 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 2). Nitroxide 2 can cross the blood-brain barrier and is then hydrolyzed in situ by esterases to regenerate nitroxide 1, which becomes entrapped in brain tissue. Seeking to improve the loading of nitroxides into brain, we synthesized the more lipophilic pentanoyloxymethyl ester, 3-pentanoyloxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (nitroxide 3). We report that the higher lipophilicity of nitroxide 3 does not significantly increase its ability to generate EPR signals in the mouse brain. Therefore, irrespective of whether nitroxide 2 or 3 was injected, similar levels of nitroxide were entrapped in brain tissue. These findings suggest that nitroxides 2 and 3 perform comparably well as proimaging agents for measuring O(2) distribution in brain.
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Affiliation(s)
- Minoru Miyake
- Center of Biomedical Research Excellence, College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, USA
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14
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Burks SR, Makowsky MA, Yaffe ZA, Hoggle C, Tsai P, Muralidharan S, Bowman MK, Kao JP, Rosen GM. The effect of structure on nitroxide EPR spectral linewidth. J Org Chem 2010; 75:4737-41. [PMID: 20540511 PMCID: PMC2914483 DOI: 10.1021/jo1005747] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitroxides with narrow linewidths are essential for low-frequency EPR spectroscopy and in vivo EPR imaging. In developing a framework for designing narrow-line nitroxides, we sought to understand the unexpectedly narrow line width of 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxyl (5). Computational modeling revealed that the carbonyl double bond in the 4-position allows conformational diversity that results in the observed narrowing of the EPR spectral line. In view of this finding, we synthesized two new nitroxides bearing an exocyclic double bond: 4-methoxycarbonylmethylidene-2,2,6,6-tetramethyl-1-piperidinyloxyl (7) and 4-acetoxymethoxycarbonylmethylidene-2,2,6,6-tetramethyl-1-piperidinyloxyl (9). These nitroxides, like nitroxide 5, exhibited narrow linewidths-consistent with the results of modeling. Nitroxide 8 (4-carboxymethylidene-2,2,6,6-tetramethyl-1-piperidinyloxyl), as a prototype, allows for a variety of structural diversity, such as nitroxide 9,that can, for instance, target tissue compartments for in vivo EPR imaging.
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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, MD 21201
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
| | - Mallory A. Makowsky
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201
| | - Zachary A. Yaffe
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201
| | - Chad Hoggle
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201
| | - Pei Tsai
- Center for Biomedical Engineering and Technology, and Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, MD 21201
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201
| | - Sukumaran Muralidharan
- Center for Biomedical Engineering and Technology, and Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, MD 21201
| | - Michael K. Bowman
- Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487
| | - Joseph P.Y. Kao
- Center for Biomedical Engineering and Technology, and Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, MD 21201
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
| | - Gerald M. Rosen
- Center for Biomedical Engineering and Technology, and Center for EPR Imaging In Vivo Physiology, University of Maryland, Baltimore, MD 21201
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201
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15
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Direct visualization of mouse brain oxygen distribution by electron paramagnetic resonance imaging: application to focal cerebral ischemia. J Cereb Blood Flow Metab 2009; 29:1695-703. [PMID: 19675560 PMCID: PMC3633216 DOI: 10.1038/jcbfm.2009.89] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Electron paramagnetic resonance imaging (EPRI) is a new modality for visualizing O(2) distribution in tissues, such as the brain after stroke or after administration of drugs of abuse. We have recently shown that 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl [1] is a pro-imaging agent that can cross the blood-brain barrier. After hydrolysis by esterases, the anion of 3-carboxy-2,2,5,5-tetramethyl-1-tetramethyl-1-pyrrolidinyloxyl [2] is trapped in brain tissue. In this study, we investigated the feasibility of using this to map the changes of O(2) concentration in mouse brain after focal ischemia. The decrease in tissue O(2) concentration in the ischemic region of mouse brain was clearly visualized by EPRI. The hypoxic zone mapped by EPRI was spatially well correlated with the infarction area in the brain imaged by diffusion-weighted magnetic resonance imaging (MRI). Finally, we observed a decrease in the size of the hypoxic region when the mouse breathed higher levels of O(2). This finding suggests that EPRI with specifically designed nitroxides is a promising imaging modality for visualizing O(2) distribution in brain tissue, especially in an ischemic brain. We believe that this imaging method can be used for monitoring the effects of therapeutic intervention aimed at enhancing brain O(2) supply, which is crucial in minimizing brain injury after stroke.
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16
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Zhelev Z, Bakalova R, Aoki I, Matsumoto KI, Gadjeva V, Anzai K, Kanno I. Nitroxyl radicals for labeling of conventional therapeutics and noninvasive magnetic resonance imaging of their permeability for blood-brain barrier: relationship between structure, blood clearance, and MRI signal dynamic in the brain. Mol Pharm 2009; 6:504-12. [PMID: 19718801 DOI: 10.1021/mp800175k] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The present study describes a novel nonradioactive methodology for in vivo noninvasive, real-time imaging of blood-brain barrier (BBB) permeability for conventional drugs, using nitroxyl radicals as spin-labels and magnetic resonance imaging (MRI). Two TEMPO-labeled analogues (SLENU and SLCNUgly) of the anticancer drug lomustine [1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea] were synthesized, using a substitution of the cyclohexyl part with nitroxyl radical. Nonmodified nitroxyl radical TEMPOL was used for comparison. The nitroxyl derivatives were injected intravenously in healthy mice via the tail vein, and MR imaging of the brain was performed on a 7.0 T MRI. The MRI signal dynamic of SLENU and SLCNUgly followed the same kinetics as nonmodified TEMPO radical. SLENU and SLCNUgly were rapidly transported and randomly distributed in the brain tissue, which indicated that the exchange of cyclohexyl part of lomustine with TEMPO radical did not suppress the permeability of the anticancer drug for BBB. The selected nitroxyl derivatives possessed different hydrophobicity, cell permeabilization ability, and blood clearance. Based on these differences, we investigated the relationship betweenthe structure of nitroxyl derivatives, their half-life in the circulation, and their MRI signal dynamic in the brain. This information was important for estimation of the merits and demerits of the described methodology and finding pathways for overcoming the restrictions.
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Affiliation(s)
- Zhivko Zhelev
- Department of Biophysics, Molecular Imaging Center, and Center for Heavy-ion Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
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17
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Burks SR, Barth ED, Halpern HJ, Rosen GM, Kao JPY. Cellular uptake of electron paramagnetic resonance imaging probes through endocytosis of liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:2301-8. [PMID: 19712666 DOI: 10.1016/j.bbamem.2009.08.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 07/27/2009] [Accepted: 08/17/2009] [Indexed: 12/01/2022]
Abstract
Electron paramagnetic resonance imaging (EPRI) allows detection and localization of paramagnetic spin probes in vivo and in real time. We have shown that nitroxide spin probes entrapped in the intracellular milieu can be imaged by EPRI. Therefore, with the development of a tumor-targetable vehicle that can efficiently deliver nitroxides into cells, it should be possible to use nitroxide spin probes to label and image cells in a tumor. In this study, we assess the potential of liposomes as a delivery vehicle for imaging probes. We demonstrate that liposomes can stably encapsulate nitroxides at very high concentrations (>100 mM), at which nitroxides exhibit concentration-dependent quenching of their EPR signal-a process analogous to the quenching of fluorescent molecules. The encapsulating liposomes thus appear spectroscopically "dark". When the liposomes are endocytosed and degraded by cells, the encapsulated nitroxides are liberated and diluted into the much larger intracellular volume. The consequent relief of quenching generates a robust intracellular nitroxide signal that can be imaged. We show that through endocytosis of nitroxide-loaded liposomes, CV1 cells can achieve intracellular nitroxide concentrations of approximately 1 mM. By using tissue phantom models, we verify that this concentration is more than sufficient for in vivo EPR imaging.
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Affiliation(s)
- Scott R Burks
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
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18
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Liu Y, Villamena FA, Sun J, Wang TY, Zweier JL. Esterified trityl radicals as intracellular oxygen probes. Free Radic Biol Med 2009; 46:876-83. [PMID: 19135524 PMCID: PMC2673998 DOI: 10.1016/j.freeradbiomed.2008.12.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 11/17/2008] [Accepted: 12/11/2008] [Indexed: 10/21/2022]
Abstract
Triarylmethyl (trityl) radicals exhibit high stability and narrow linewidth under physiological conditions which provide high sensitivity and resolution for the measurement of O2 concentrations, making them attractive as EPR oximetry probes. However, the application of previously available compounds has been limited by their poor intracellular permeability. We recently reported the synthesis and characterization of esterified trityl radicals as potential intracellular EPR probes and their oxygen sensitivity, redox properties, and enzyme-mediated hydrolysis were investigated. In this paper, we report the cellular permeability and stability of these trityls in the presence of bovine aortic endothelial cells. Results show that the acetoxymethoxycarbonyl-containing trityl AMT-02 exhibits high stability in the presence of cells and can be effectively internalized. The intracellular hydrolysis of AMT-02 to the carboxylate form of the trityl (CT-03) was also observed. In addition, this internalized trityl probe was applied to measure intracellular O2 concentrations and the effects of menadione and KCN on the rates of O2 consumption in endothelial cells. This study demonstrates that these esterified trityl radicals can function as effective EPR oximetry probes measuring intracellular O2 concentration and consumption.
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Affiliation(s)
- Yangping Liu
- Center for Biomedical EPR Spectroscopy and Imaging, The Davis Heart and Lung Research Institute, Division of Cardiovascular Medicine, Department of Internal Medicine, Columbus, OH 43210, USA
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19
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Sato-Akaba H, Fujii H, Hirata H. Improvement of temporal resolution for three-dimensional continuous-wave electron paramagnetic resonance imaging. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:123701. [PMID: 19123563 DOI: 10.1063/1.3033161] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
This paper describes improved temporal resolution for three-dimensional (3D) continuous-wave electron paramagnetic resonance (EPR) imaging. To improve temporal resolution, the duration of magnetic filed scanning that is used to obtain an EPR spectrum for each projection was reduced to 40 ms. The Helmholtz coil pair for field scanning was driven by triangular waves. The uniform distribution of projections was also used to reduce the number of projections for 3D image reconstruction. The reduction reaction of 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy with ascorbic acid was visualized by improved 3D EPR imaging techniques with a temporal resolution of 5.8 s.
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Affiliation(s)
- Hideo Sato-Akaba
- Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814, Japan
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20
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Burks SR, Ni J, Muralidharan S, Coop A, Kao JPY, Rosen GM. Optimization of labile esters for esterase-assisted accumulation of nitroxides into cells: a model for in vivo EPR imaging. Bioconjug Chem 2008; 19:2068-71. [PMID: 18783260 DOI: 10.1021/bc8001562] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nitroxide-based electron paramagnetic resonance (EPR) imaging agents are useful quantitative probes of O2 concentration in vivo in real time. Lipophilic, labile alkanoyloxymethyl esters of nitroxides can cross the blood-brain barrier, and after hydrolysis, the corresponding anionic nitroxide is intracellularly entrapped at levels sufficient to permit O2 measurements. The utility of nitroxides as EPR imaging agents depends critically on their ability to accumulate in the brain to high levels. In this study, we systematically investigated the relationship between the structure of the alkanoyl moiety and the ability of the corresponding labile ester to deliver nitroxide intracellularly. We demonstrate, in a cultured cell model, that for nitroxide labile esters with unbranched alkanoyl chains, increasing the chain length improves intracellular loading. Moreover, by studying an isomeric series of labile esters, we conclude that branching of the alkanoyl chain drastically reduces intracellular loading. These structural insights improve our general ability to use labile esters to deliver carboxylates intracellularly, and suggest a strategy for enhancing delivery of nitroxide imaging agents across the blood-brain barrier in a living animal.
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Affiliation(s)
- Scott R Burks
- Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, Maryland 21201, USA
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21
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Sato-Akaba H, Fujii H, Hirata H. Development and testing of a CW-EPR apparatus for imaging of short-lifetime nitroxyl radicals in mouse head. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 193:191-198. [PMID: 18502159 DOI: 10.1016/j.jmr.2008.04.035] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2008] [Revised: 04/20/2008] [Accepted: 04/24/2008] [Indexed: 05/26/2023]
Abstract
This article describes a method for reducing the acquisition time in three-dimensional (3D) continuous-wave electron paramagnetic resonance (CW-EPR) imaging. To visualize nitroxyl spin probes, which have a short lifetime in living organisms, the acquisition time for a data set of spectral projections should be shorter than the lifetime of the spin probes. To decrease the total time required for data acquisition, the duration of magnetic field scanning was reduced to 0.5s. Moreover, the number of projections was decreased by using the concept of a uniform distribution. To demonstrate this faster data acquisition, two kinds of nitroxyl radicals with different decay rates were measured in mice. 3D EPR imaging of 4-hydroxy-2,2,6,6-tetramethylpiperidine-d17-1-15N-1-oxyl in mouse head was successfully carried out. 3D EPR imaging of nitroxyl spin probes with a half-life of a few minutes was achieved for the first time in live animals.
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Affiliation(s)
- Hideo Sato-Akaba
- Department of Electrical Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
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22
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Miyake M, Shen J, Liu S, Shi H, Liu W, Yuan Z, Pritchard A, Kao JPY, Liu KJ, Rosen GM. Acetoxymethoxycarbonyl nitroxides as electron paramagnetic resonance proimaging agents to measure O2 levels in mouse brain: a pharmacokinetic and pharmacodynamic study. J Pharmacol Exp Ther 2006; 318:1187-93. [PMID: 16757536 DOI: 10.1124/jpet.106.106245] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Measurement of O(2) concentration and distribution in brain is essential to understanding the pathophysiology of stroke. Low-frequency electron paramagnetic resonance (EPR) spectroscopy with a paramagnetic probe is an attractive imaging modality that can potentially map O(2) concentration in the brain. In a previous study, we demonstrated that, after intraperitoneal administration of 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (1) to mice, this nitroxide crossed the blood-brain barrier into brain tissue where, after hydrolysis, 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (2) was liberated and entrapped. This pilot study suggested that nitroxide 1 is a proimaging agent that can deliver nitroxide 2 to brain tissue, where O(2) levels can be estimated. In the present study, we conducted a series of pharmacokinetic and pharmacodynamic experiments designed to assess the uptake of structurally disparate nitroxides into brain tissue and retention, after hydrolysis, of the anions of the corresponding nitroxide acids. From these findings, nitroxide 1 and trans-3,4-di(acetoxymethoxycarbonyl)-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (5) meet the requirement as EPR proimaging agents for mapping O(2) distribution in the brain following stroke.
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