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Gram M, Christa M, Gutjahr FT, Albertova P, Williams T, Jakob PM, Bauer WR, Nordbeck P. Quantification of the rotating frame relaxation time T 2ρ: Comparison of balanced spin-lock and continuous-wave Malcolm-Levitt preparations. NMR IN BIOMEDICINE 2024; 37:e5199. [PMID: 38924172 DOI: 10.1002/nbm.5199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 04/09/2024] [Accepted: 05/12/2024] [Indexed: 06/28/2024]
Abstract
For the quantification of rotating frame relaxation times, the T2ρ relaxation pathway plays an essential role. Nevertheless, T2ρ imaging has been studied only to a small extent compared with T1ρ, and preparation techniques for T2ρ have so far been adapted from T1ρ methods. In this work, two different preparation concepts are compared specifically for the use of T2ρ mapping. The first approach involves transferring the balanced spin-locking (B-SL) concept of T1ρ imaging. The second and newly proposed approach is a continuous-wave Malcolm-Levitt (CW-MLEV) pulse train with zero echo times and was motivated from T2 preparation strategies. The modules are tested in Bloch simulations for their intrinsic sensitivity to field inhomogeneities and validated in phantom experiments. In addition, myocardial T2ρ mapping was performed in mice as an exemplary application. Our results demonstrate that the CW-MLEV approach provides superior robustness and thus suggest that established methods of T1ρ imaging are not best suited for T2ρ experiments. In the presence of field inhomogeneities, the simulations indicated an increased banding compensation by a factor of 4.1 compared with B-SL. Quantification of left ventricular T2ρ time in mice yielded more consistent results, and values in the range of 59.2-61.1 ms (R2 = 0.986-0.992) were observed at 7 T.
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Affiliation(s)
- Maximilian Gram
- Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany
- Experimental Physics 5, University of Würzburg, Würzburg, Germany
| | - Martin Christa
- Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany
- Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg, Würzburg, Germany
| | | | - Petra Albertova
- Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany
- Experimental Physics 5, University of Würzburg, Würzburg, Germany
| | - Tatjana Williams
- Department of Cardiovascular Genetics, Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg, Würzburg, Germany
| | | | - Wolfgang Rudolf Bauer
- Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany
- Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg, Würzburg, Germany
| | - Peter Nordbeck
- Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany
- Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg, Würzburg, Germany
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Donnelly SC, Varela-Mattatall GE, Hassan S, Sun Q, Gelman N, Thiessen JD, Thompson RT, Prato FS, Burton JP, Goldhawk DE. Bacterial association with metals enables in vivo monitoring of urogenital microbiota using magnetic resonance imaging. Commun Biol 2024; 7:1079. [PMID: 39227641 PMCID: PMC11371927 DOI: 10.1038/s42003-024-06783-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 08/26/2024] [Indexed: 09/05/2024] Open
Abstract
Bacteria constitute a significant part of the biomass of the human microbiota, but their interactions are complex and difficult to replicate outside the host. Exploiting the superior resolution of magnetic resonance imaging (MRI) to examine signal parameters of selected human isolates may allow tracking of their dispersion throughout the body. Here we investigate longitudinal and transverse MRI relaxation rates and found significant differences between several bacterial strains. Common commensal strains of lactobacilli display notably high MRI relaxation rates, partially explained by elevated cellular manganese content, while other species contain more iron than manganese. Lactobacillus crispatus show particularly high values, 4-fold greater than any other species; up to 60-fold greater signal than relevant tissue background; and a linear relationship between relaxation rate and fraction of live cells. Different bacterial strains have detectable, repeatable MRI relaxation rates that in the future may enable monitoring of their persistence in the human body for enhanced molecular imaging.
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Affiliation(s)
- Sarah C Donnelly
- Imaging, Lawson Research Institute, London, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Canada
- Microbiology & Immunology, Western University, London, Canada
| | - Gabriel E Varela-Mattatall
- Imaging, Lawson Research Institute, London, Canada
- Medical Biophysics, Western University, London, Canada
| | | | - Qin Sun
- Imaging, Lawson Research Institute, London, Canada
- Medical Biophysics, Western University, London, Canada
| | - Neil Gelman
- Imaging, Lawson Research Institute, London, Canada
- Medical Biophysics, Western University, London, Canada
- Medical Imaging, Western University, London, Canada
| | - Jonathan D Thiessen
- Imaging, Lawson Research Institute, London, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Canada
- Medical Biophysics, Western University, London, Canada
| | - R Terry Thompson
- Imaging, Lawson Research Institute, London, Canada
- Medical Biophysics, Western University, London, Canada
- Physics & Astronomy, Western University, London, Canada
| | - Frank S Prato
- Imaging, Lawson Research Institute, London, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Canada
- Medical Biophysics, Western University, London, Canada
- Medical Imaging, Western University, London, Canada
| | - Jeremy P Burton
- Microbiology & Immunology, Western University, London, Canada
- Division of Urology and Surgery, Western University, London, Canada
- Centre for Human Microbiome Research, Lawson Research Institute, London, Canada
| | - Donna E Goldhawk
- Imaging, Lawson Research Institute, London, Canada.
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Canada.
- Medical Biophysics, Western University, London, Canada.
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Qadri Z, Righi V, Li S, Tzika AA. Tracking of Labelled Stem Cells Using Molecular MR Imaging in a Mouse Burn Model in Vivo as an Approach to Regenerative Medicine. ACTA ACUST UNITED AC 2021; 11:1-15. [PMID: 33996249 PMCID: PMC8118598 DOI: 10.4236/ami.2021.111001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Therapies based on stem cell transplants offer significant potential in the field of regenerative medicine. Monitoring the fate of the transplanted stem cells in a timely manner is considered one of the main limitations for long-standing success of stem cell transplants. Imaging methods that visualize and track stem cells in vivo non-invasively in real time are helpful towards the development of successful cell transplantation techniques. Novel molecular imaging methods which are non-invasive particularly such as MRI have been of great recent interest. Hence, mouse models which are of clinical relevance have been studied by injecting contrast agents used for labelling cells such as super-paramagnetic iron-oxide (SPIO) nanoparticles for cellular imaging. The MR techniques which can be used to generate positive contrast images have been of much relevance recently for tracking of the labelled cells. Particularly when the off-resonance region in the vicinity of the labeled cells is selectively excited while suppressing the signals from the non-labeled regions by the method of spectral dephasing. Thus, tracking of magnetically labelled cells employing positive contrast in vivo MR imaging methods in a burn mouse model in a non-invasive way has been the scope of this study. The consequences have direct implications for monitoring labeled stem cells at some stage in wound healing. We suggest that our approach can be used in clinical trials in molecular and regenerative medicine.
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Affiliation(s)
- Zeba Qadri
- MGH NMR Surgical Laboratory, Center for Surgery, Innovation and Bioengineering, Department of Surgery, Massachusetts General and Shriners Burn Hospitals, Harvard Medical School, Boston, USA.,Athinoula A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School Charlestown, USA
| | - Valeria Righi
- MGH NMR Surgical Laboratory, Center for Surgery, Innovation and Bioengineering, Department of Surgery, Massachusetts General and Shriners Burn Hospitals, Harvard Medical School, Boston, USA.,Athinoula A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School Charlestown, USA
| | - Shasha Li
- MGH NMR Surgical Laboratory, Center for Surgery, Innovation and Bioengineering, Department of Surgery, Massachusetts General and Shriners Burn Hospitals, Harvard Medical School, Boston, USA.,Athinoula A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School Charlestown, USA
| | - A Aria Tzika
- MGH NMR Surgical Laboratory, Center for Surgery, Innovation and Bioengineering, Department of Surgery, Massachusetts General and Shriners Burn Hospitals, Harvard Medical School, Boston, USA.,Athinoula A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School Charlestown, USA
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Righi V, Starkey M, Dai G, Rahme LG, Tzika AA. Magnetization transfer contrast MRI in GFP‑tagged live bacteria. Mol Med Rep 2018; 19:617-621. [PMID: 30483743 PMCID: PMC6297796 DOI: 10.3892/mmr.2018.9669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 05/22/2018] [Indexed: 11/29/2022] Open
Abstract
Green fluorescent protein (GFP) is a widely utilized molecular reporter of gene expression. However, its use in in vivo imaging has been restricted to transparent tissue mainly due to the tissue penetrance limitation of optical imaging. Magnetization transfer contrast (MTC) is a magnetic resonance imaging (MRI) methodology currently utilized to detect macromolecule changes such as decrease in myelin and increase in collagen content. MTC MRI imaging was performed to detect GFP in both in vitro cells and in an in vivo mouse model to determine if MTC imaging could be used to detect infection from Pseudomonas aeruginosa in murine tissues. It was demonstrated that the approach produces values that are protein specific and concentration dependent. This method provides a valuable, non-invasive imaging tool to study the impact of novel antibacterial therapeutics on bacterial proliferation and perhaps viability within the host system, and could potentially suggest the modulation of bacterial gene expression within the host when exposed to such compounds.
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Affiliation(s)
- Valeria Righi
- NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Melissa Starkey
- Molecular Surgery Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, MA 02114, USA
| | - George Dai
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA 02114, USA
| | - Laurence G Rahme
- Molecular Surgery Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, MA 02114, USA
| | - Aria A Tzika
- NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Hospital, Harvard Medical School, Boston, MA 02114, USA
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Quantification of susceptibility change at high-concentrated SPIO-labeled target by characteristic phase gradient recognition. Magn Reson Imaging 2015; 34:552-61. [PMID: 26592796 DOI: 10.1016/j.mri.2015.11.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Revised: 11/04/2015] [Accepted: 11/17/2015] [Indexed: 11/21/2022]
Abstract
Phase map cross-correlation detection and quantification may produce highlighted signal at superparamagnetic iron oxide nanoparticles, and distinguish them from other hypointensities. The method may quantify susceptibility change by performing least squares analysis between a theoretically generated magnetic field template and an experimentally scanned phase image. Because characteristic phase recognition requires the removal of phase wrap and phase background, additional steps of phase unwrapping and filtering may increase the chance of computing error and enlarge the inconsistence among algorithms. To solve problem, phase gradient cross-correlation and quantification method is developed by recognizing characteristic phase gradient pattern instead of phase image because phase gradient operation inherently includes unwrapping and filtering functions. However, few studies have mentioned the detectable limit of currently used phase gradient calculation algorithms. The limit may lead to an underestimation of large magnetic susceptibility change caused by high-concentrated iron accumulation. In this study, mathematical derivation points out the value of maximum detectable phase gradient calculated by differential chain algorithm in both spatial and Fourier domain. To break through the limit, a modified quantification method is proposed by using unwrapped forward differentiation for phase gradient generation. The method enlarges the detectable range of phase gradient measurement and avoids the underestimation of magnetic susceptibility. Simulation and phantom experiments were used to quantitatively compare different methods. In vivo application performs MRI scanning on nude mice implanted by iron-labeled human cancer cells. Results validate the limit of detectable phase gradient and the consequent susceptibility underestimation. Results also demonstrate the advantage of unwrapped forward differentiation compared with differential chain algorithms for susceptibility quantification at high-concentrated iron accumulation.
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Keenan KE, Besier TF, Pauly JM, Smith RL, Delp SL, Beaupre GS, Gold GE. T1ρ Dispersion in Articular Cartilage: Relationship to Material Properties and Macromolecular Content. Cartilage 2015; 6:113-22. [PMID: 26069714 PMCID: PMC4462251 DOI: 10.1177/1947603515569529] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
OBJECTIVE This study assessed T1ρ relaxation dispersion, measured by magnetic resonance imaging (MRI), as a tool to noninvasively evaluate cartilage material and biochemical properties. The specific objective was to answer two questions: (1) does cartilage initial elastic modulus (E 0) correlate with T1ρ dispersion effects and (2) does collagen or proteoglycan content correlate with T1ρ dispersion effects? DESIGN Cadaveric patellae with and without visible cartilage damage on conventional MR were included. T2 and T1ρ relaxation times at 500 and 1000 Hz spin-lock field amplitudes were measured. We estimated T1ρ dispersion effects by measuring T1ρ relaxation time at 500 and 1000 Hz and T2 relaxation time and using a new tool, the ratio T1ρ/T2. Cartilage initial elastic modulus, E 0, was measured from initial response of mechanical indentation creep tests. Collagen and proteoglycan contents were measured at the indentation test sites; proteoglycan content was measured by their covalently linked sulfated glycosaminoglycans (sGAG). Pearson correlation coefficients were determined, taking into account the clustering of multiple samples within a single patella specimen. RESULTS Cartilage initial elastic modulus, E 0, increased with decreasing values of T1ρ/T2 measurements at both 500 Hz (P = 0.034) and 1000 Hz (P = 0.022). 1/T1ρ relaxation time (500 Hz) increased with increasing sGAG content (P = 0.041). CONCLUSIONS T1ρ/T2 ratio, a new tool, and cartilage initial elastic modulus are both measures of water-protein interactions, are dependent on the cartilage structure, and were correlated in this study.
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Affiliation(s)
- Kathryn E. Keenan
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Thor F. Besier
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - John M. Pauly
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - R. Lane Smith
- Department of Orthopaedic Surgery, Stanford University, Stanford, CA, USA,Rehabilitation R&D Musculoskeletal Research Laboratory, Department of Veterans Affairs, Palo Alto, CA, USA
| | - Scott L. Delp
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA,Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Gary S. Beaupre
- Rehabilitation R&D Musculoskeletal Research Laboratory, Department of Veterans Affairs, Palo Alto, CA, USA
| | - Garry E. Gold
- Department of Orthopaedic Surgery, Stanford University, Stanford, CA, USA,Department of Bioengineering, Stanford University, Stanford, CA, USA,Department of Radiology, Stanford University, Stanford, CA, USA
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Navarathna DHMLP, Munasinghe J, Lizak MJ, Nayak D, McGavern DB, Roberts DD. MRI confirms loss of blood-brain barrier integrity in a mouse model of disseminated candidiasis. NMR IN BIOMEDICINE 2013; 26:1125-1134. [PMID: 23606437 PMCID: PMC3744627 DOI: 10.1002/nbm.2926] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 10/25/2012] [Accepted: 01/02/2013] [Indexed: 06/02/2023]
Abstract
Disseminated candidiasis primarily targets the kidneys and brain in mice and humans. Damage to these critical organs leads to the high mortality associated with such infections, and invasion across the blood-brain barrier can result in fungal meningoencephalitis. Candida albicans can penetrate a brain endothelial cell barrier in vitro through transcellular migration, but this mechanism has not been confirmed in vivo. MRI using the extracellular vascular contrast agent gadolinium diethylenetriaminepentaacetic acid demonstrated that integrity of the blood-brain barrier is lost during C. albicans invasion. Intravital two-photon laser scanning microscopy was used to provide the first real-time demonstration of C. albicans colonizing the living brain, where both yeast and filamentous forms of the pathogen were found. Furthermore, we adapted a previously described method utilizing MRI to monitor inflammatory cell recruitment into infected tissues in mice. Macrophages and other phagocytes were visualized in kidney and brain by the administration of ultrasmall iron oxide particles. In addition to obtaining new insights into the passage of C. albicans across the brain microvasculature, these imaging methods provide useful tools to study further the pathogenesis of C. albicans infections, to define the roles of Candida virulence genes in kidney versus brain infection and to assess new therapeutic measures for drug development.
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Affiliation(s)
- Dhammika H. M. L. P. Navarathna
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Jeeva Munasinghe
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Martin J. Lizak
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Debasis Nayak
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Dorian B. McGavern
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - David D. Roberts
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
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Papagiannaros A, Righi V, Day GG, Rahme LG, Liu PK, Fischman AJ, Tompkins RG, Tzika AA. Imaging C-Fos Gene Expression in Burns Using Lipid Coated Spion Nanoparticles. ADVANCES IN MOLECULAR IMAGING 2012; 2:31-37. [PMID: 24995147 DOI: 10.4236/ami.2012.24005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
MR imaging of gene transcription is important as it should enable the non-invasive detection of mRNA alterations in disease. A range of MRI methods have been proposed for in vivo molecular imaging of cells based on the use of ultra-small super-paramagnetic iron oxide (USPIO) nanoparticles and related susceptibility weighted imaging methods. Although immunohistochemistry can robustly differentiate the expression of protein variants, there is currently no direct gene assay technique that is capable of differentiating established to differentiate the induction profiles of c-Fos mRNA in vivo. To visualize the differential FosB gene expression profile in vivo after burn trauma, we developed MR probes that link the T2* contrast agent [superparamagnetic iron oxide nanoparticles (SPION)] with an oligodeoxynucleotide (ODN) sequence complementary to FosB mRNA to visualize endogenous mRNA targets via in vivo hybridization. The presence of this SPION-ODN probe in cells results in localized signal reduction in T2*-weighted MR images, in which the rate of signal reduction (R2*) reflects the regional iron concentration at different stages of amphetamine (AMPH) exposure in living mouse tissue. Our aim was to produce a superior contrast agent that can be administered using systemic as opposed to local administration and which will target and accumulate at sites of burn injury. Specifically, we developed and evaluated a PEGylated lipid coated MR probe with ultra-small super-paramagnetic iron oxide nanoparticles (USPION, a T2 susceptibility agent) coated with cationic fusogenic lipids, used for cell transfection and gene delivery and covalently linked to a phosphorothioate modified oligodeoxynucleotide (sODN) complementary to c-Fos mRNA (SPION-cFos) and used the agent to image mice with leg burns. Our study demonstrated the feasibility of monitoring burn injury using MR imaging of c-Fos transcription in vivo, in a clinically relevant mouse model of burn injury for the first time.
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Affiliation(s)
- Aristarchos Papagiannaros
- NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, USA
| | - Valeria Righi
- NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, USA ; Athinoula A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, USA ; Department of Biochemistry "G. Moruzzi", University of Bologna, Bologna, Italy
| | - George G Day
- Athinoula A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, USA
| | - Laurence G Rahme
- Molecular Surgery Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School and Massachusetts General Hospital, Boston, USA ; Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, USA
| | - Philip K Liu
- Athinoula A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, USA
| | - Alan J Fischman
- Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, USA
| | - Ronald G Tompkins
- Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, USA
| | - A Aria Tzika
- NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, USA ; Athinoula A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, USA ; Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, USA
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Faucher L, Tremblay M, Lagueux J, Gossuin Y, Fortin MA. Rapid synthesis of PEGylated ultrasmall gadolinium oxide nanoparticles for cell labeling and tracking with MRI. ACS APPLIED MATERIALS & INTERFACES 2012; 4:4506-4515. [PMID: 22834680 DOI: 10.1021/am3006466] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Ultrasmall paramagnetic Gd(2)O(3) nanoparticles have been developed as contrast agents for molecular and cellular preclinical MRI procedures. These small particles (mean diameter <5 nm) have the highest Gd density of all paramagnetic contrast agents. They generate strong positive contrast enhancement in T(1)-weighted MRI. Signal enhancement is modulated by the interactions of water molecules with Gd, and very small particles provide the optimal surface-to-volume ratios necessary to reach high relaxivities. Conventional Gd(2)O(3) nanocrystal synthesis techniques, and subsequent polyethylene glycol (PEG) grafting procedures are usually time-consuming and recovery losses are also limitative. The present study reports on a new, fast, and efficient one-pot Gd(2)O(3) synthesis technique that provides PEGylated nanoparticles of very small size (mean diameter = 1.3 nm). Readily coated with PEG, the particles are colloidally stable in aqueous media and provide high longitudial relaxivities and small r(2)/r(1) ratios (r(1) = 14.2 mM(-1) s(-1) at 60 MHz; r(2)/r(1) = 1.20), ideal for T(1)-weighted MRI. In this study, F98 brain cancer cells (glioblastoma multiforme) were labeled with the contrast agent and implanted in vivo (mice brains). The labeled cells appeared positively contrasted at least 48 h after implantation. Each one of the implanted animals developed a brain tumor. The performance of PEG-Gd(2)O(3) was also compared with that of commercially available iron oxide nanoparticles. This study demonstrated that ultrasmall PEG-Gd(2)O(3) nanoparticles provide strong positive contrast enhancement in T(1)-weighted imaging, and allow the visualization of labeled cells implanted in vivo.
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Affiliation(s)
- Luc Faucher
- Axe métabolisme, santé vasculaire et rénale, Centre hospitalier universitaire de Québec (CRCHUQ-MSVR), 10 rue de l'Espinay, Québec, G1L 3L5, Canada
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