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Shchepin RV, Goodson BM, Theis T, Warren WS, Chekmenev EY. Toward Hyperpolarized 19 F Molecular Imaging via Reversible Exchange with Parahydrogen. Chemphyschem 2017; 18:1961-1965. [PMID: 28557156 DOI: 10.1002/cphc.201700594] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Indexed: 01/16/2023]
Abstract
Fluorine-19 has high NMR detection sensitivity-similar to that of protons-owing to its large gyromagnetic ratio and high natural abundance (100 %). Unlike protons, however, fluorine-19 (19 F) has a negligible occurrence in biological objects, as well as a more sensitive chemical shift. As a result, in vivo 19 F NMR spectroscopy and MR imaging offer advantages of negligible background signal and sensitive reporting of the local molecular environment. Here we report on NMR hyperpolarization of 19 F nuclei using reversible exchange reactions with parahydrogen gas as the source of nuclear spin order. NMR signals of 3-fluoropyridine were enhanced by ≈100 fold, corresponding to 0.3 % 19 F nuclear spin polarization (at 9.4 T), using about 50 % parahydrogen. While future optimization efforts will likely significantly increase the hyperpolarization levels, we already demonstrate the utility of 19 F hyperpolarization for high-resolution hyperpolarized 19 F imaging and hyperpolarized 19 F pH sensing.
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52
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Shchepin RV, Barskiy DA, Coffey AM, Feldman MA, Kovtunova LM, Bukhtiyarov VI, Kovtunov KV, Goodson BM, Koptyug IV, Chekmenev EY. Robust Imidazole‐
15
N
2
Synthesis for High‐Resolution Low‐Field (0.05 T)
15
N Hyperpolarized NMR Spectroscopy. ChemistrySelect 2017. [DOI: 10.1002/slct.201700718] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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53
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Barskiy DA, Shchepin RV, Tanner CPN, Colell JFP, Goodson BM, Theis T, Warren WS, Chekmenev EY. The Absence of Quadrupolar Nuclei Facilitates Efficient
13
C Hyperpolarization via Reversible Exchange with Parahydrogen. Chemphyschem 2017; 18:1493-1498. [DOI: 10.1002/cphc.201700416] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Indexed: 12/16/2022]
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54
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Barskiy DA, Coffey AM, Nikolaou P, Mikhaylov DM, Goodson BM, Branca RT, Lu GJ, Shapiro MG, Telkki VV, Zhivonitko VV, Koptyug IV, Salnikov OG, Kovtunov KV, Bukhtiyarov VI, Rosen MS, Barlow MJ, Safavi S, Hall IP, Schröder L, Chekmenev EY. Frontispiece: NMR Hyperpolarization Techniques of Gases. Chemistry 2017. [DOI: 10.1002/chem.201780461] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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55
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Barskiy DA, Coffey AM, Nikolaou P, Mikhaylov DM, Goodson BM, Branca RT, Lu GJ, Shapiro MG, Telkki VV, Zhivonitko VV, Koptyug IV, Salnikov OG, Kovtunov KV, Bukhtiyarov VI, Rosen MS, Barlow MJ, Safavi S, Hall IP, Schröder L, Chekmenev EY. NMR Hyperpolarization Techniques of Gases. Chemistry 2017; 23:725-751. [PMID: 27711999 PMCID: PMC5462469 DOI: 10.1002/chem.201603884] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2016] [Indexed: 01/09/2023]
Abstract
Nuclear spin polarization can be significantly increased through the process of hyperpolarization, leading to an increase in the sensitivity of nuclear magnetic resonance (NMR) experiments by 4-8 orders of magnitude. Hyperpolarized gases, unlike liquids and solids, can often be readily separated and purified from the compounds used to mediate the hyperpolarization processes. These pure hyperpolarized gases enabled many novel MRI applications including the visualization of void spaces, imaging of lung function, and remote detection. Additionally, hyperpolarized gases can be dissolved in liquids and can be used as sensitive molecular probes and reporters. This Minireview covers the fundamentals of the preparation of hyperpolarized gases and focuses on selected applications of interest to biomedicine and materials science.
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Barskiy DA, Coffey AM, Nikolaou P, Mikhaylov DM, Goodson BM, Branca RT, Lu GJ, Shapiro MG, Telkki VV, Zhivonitko VV, Koptyug IV, Salnikov OG, Kovtunov KV, Bukhtiyarov VI, Rosen MS, Barlow MJ, Safavi S, Hall IP, Schröder L, Chekmenev EY. Cover Picture: NMR Hyperpolarization Techniques of Gases (Chem. Eur. J. 4/2017). Chemistry 2017. [DOI: 10.1002/chem.201604810] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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57
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Barskiy DA, Coffey AM, Nikolaou P, Mikhaylov DM, Goodson BM, Branca RT, Lu GJ, Shapiro MG, Telkki VV, Zhivonitko VV, Koptyug IV, Salnikov OG, Kovtunov KV, Bukhtiyarov VI, Rosen MS, Barlow MJ, Safavi S, Hall IP, Schröder L, Chekmenev EY. NMR Hyperpolarization Techniques of Gases. Chemistry 2016. [DOI: 10.1002/chem.201604827] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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58
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Shchepin RV, Barskiy DA, Coffey AM, Goodson BM, Chekmenev EY. NMR Signal Amplification by Reversible Exchange of Sulfur-Heterocyclic Compounds Found In Petroleum. ChemistrySelect 2016; 1:2552-2555. [PMID: 27500206 DOI: 10.1002/slct.201600761] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
NMR hyperpolarization via Signal Amplification by Reversible Exchange (SABRE) was employed to investigate the feasibility of enhancing the NMR detection sensitivity of sulfur-heterocycles (specifically 2-methylthiophene and dibenzothiophenes), a family of compounds typically found in petroleum and refined petroleum products. SABRE hyperpolarization of sulfur-heterocycles (conducted in seconds) offers potential advantages of providing structural information about sulfur-containing contaminants in petroleum, thereby informing petroleum purification and refining to minimize sulfur content in refined products such as gasoline. Moreover, NMR spectroscopy sensitivity gains endowed by hyperpolarization potentially allows for performing structural assays using inexpensive, low-magnetic-field (ca. 1 T) high-resolution NMR spectrometers ideally suited for industrial applications in the field.
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Shchepin RV, Barskiy DA, Coffey AM, Theis T, Shi F, Warren WS, Goodson BM, Chekmenev EY. 15N Hyperpolarization of Imidazole- 15N 2 for Magnetic Resonance pH Sensing via SABRE-SHEATH. ACS Sens 2016; 1:640-644. [PMID: 27379344 PMCID: PMC4924567 DOI: 10.1021/acssensors.6b00231] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 04/14/2016] [Indexed: 12/17/2022]
Abstract
![]()
15N nuclear spins of imidazole-15N2 were
hyperpolarized using NMR signal amplification by reversible
exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH).
A 15N NMR signal enhancement of ∼2000-fold at 9.4
T is reported using parahydrogen gas (∼50% para-) and ∼0.1
M imidazole-15N2 in methanol:aqueous buffer
(∼1:1). Proton binding to a 15N site of imidazole
occurs at physiological pH (pKa ∼
7.0), and the binding event changes the 15N isotropic chemical
shift by ∼30 ppm. These properties are ideal for in vivo pH
sensing. Additionally, imidazoles have low toxicity and are readily
incorporated into a wide range of biomolecules. 15N-Imidazole
SABRE-SHEATH hyperpolarization potentially enables pH sensing on scales
ranging from peptide and protein molecules to living organisms.
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Barskiy DA, Shchepin RV, Coffey AM, Theis T, Warren WS, Goodson BM, Chekmenev EY. Over 20% (15)N Hyperpolarization in Under One Minute for Metronidazole, an Antibiotic and Hypoxia Probe. J Am Chem Soc 2016; 138:8080-3. [PMID: 27321159 PMCID: PMC4937835 DOI: 10.1021/jacs.6b04784] [Citation(s) in RCA: 111] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Direct NMR hyperpolarization of naturally abundant (15)N sites in metronidazole is demonstrated using SABRE-SHEATH (Signal Amplification by Reversible Exchange in SHield Enables Alignment Transfer to Heteronuclei). In only a few tens of seconds, nuclear spin polarization P(15)N of up to ∼24% is achieved using parahydrogen with 80% para fraction corresponding to P(15)N ≈ 32% if ∼100% parahydrogen were employed (which would translate to a signal enhancement of ∼0.1-million-fold at 9.4 T). In addition to this demonstration on the directly binding (15)N site (using J(2)H-(15)N), we also hyperpolarized more distant (15)N sites in metronidazole using longer-range spin-spin couplings (J(4)H-(15)N and J(5)H-(15)N). Taken together, these results significantly expand the range of molecular structures and sites amenable to hyperpolarization via low-cost parahydrogen-based methods. In particular, hyperpolarized nitroimidazole and its derivatives have powerful potential applications such as direct in vivo imaging of mechanisms of action or hypoxia sensing.
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Shi F, He P, Best QA, Groome K, Truong M, Coffey AM, Zimay G, Shchepin RV, Waddell KW, Chekmenev EY, Goodson BM. Aqueous NMR Signal Enhancement by Reversible Exchange in a Single Step Using Water-Soluble Catalysts. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2016; 120:12149-12156. [PMID: 27350846 PMCID: PMC4918635 DOI: 10.1021/acs.jpcc.6b04484] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 05/11/2016] [Indexed: 05/26/2023]
Abstract
Two synthetic strategies are investigated for the preparation of water-soluble iridium-based catalysts for NMR signal amplification by reversible exchange (SABRE). In one approach, PEGylation of a variant N-heterocyclic carbene provided a novel catalyst with excellent water solubility. However, while SABRE-active in ethanol solutions, the catalyst lost activity in >50% water. In a second approach, synthesis of a novel di-iridium complex precursor where the cyclooctadiene (COD) rings have been replaced by CODDA (1,2-dihydroxy-3,7-cyclooctadiene) leads to the creation of a catalyst [IrCl(CODDA)IMes] that can be dissolved and activated in water-enabling aqueous SABRE in a single step, without need for either an organic cosolvent or solvent removal followed by aqueous reconstitution. The potential utility of the CODDA catalyst for aqueous SABRE is demonstrated with the ∼(-)32-fold enhancement of 1H signals of pyridine in water with only 1 atm of parahydrogen.
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Shchepin R, Truong ML, Theis T, Coffey AM, Shi F, Waddell K, Warren WS, Goodson BM, Chekmenev EY. Hyperpolarization of "Neat" Liquids by NMR Signal Amplification by Reversible Exchange. J Phys Chem Lett 2015; 6:1961-7. [PMID: 26029349 PMCID: PMC4442667 DOI: 10.1021/acs.jpclett.5b00782] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 05/08/2015] [Indexed: 05/20/2023]
Abstract
We report NMR Signal Amplification by Reversible Exchange (SABRE) hyperpolarization of the rare isotopes in "neat" liquids, each composed only of an otherwise pure target compound with isotopic natural abundance (n.a.) and millimolar concentrations of dissolved catalyst. Pyridine (Py) or Py derivatives are studied at 0.4% isotopic natural abundance ¹⁵N, deuterated, ¹⁵N enriched, and in various combinations using the SABRE-SHEATH variant (microTesla magnetic fields to permit direct ¹⁵N polarization from parahydrogen via reversible binding and exchange with an Ir catalyst). We find that the dilute n.a. ¹⁵N spin bath in Py still channels spin order from parahydrogen to dilute ¹⁵N spins, without polarization losses due to the presence of ¹⁴N or ²H. We demonstrate P(15N) ≈ 1% (a gain of 2900 fold relative to thermal polarization at 9.4 T) at high substrate concentrations. This fundamental finding has a significant practical benefit for screening potentially hyperpolarizable contrast agents without labeling. The capability of screening at n.a. level of ¹⁵N is demonstrated on examples of mono- and dimethyl-substituted Py (picolines and lutidines previously identified as promising pH sensors), showing that the presence of a methyl group in the ortho position significantly decreases SABRE hyperpolarization.
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63
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Truong M, Theis T, Coffey AM, Shchepin RV, Waddell KW, Shi F, Goodson BM, Warren W, Chekmenev EY. 15N Hyperpolarization by Reversible Exchange Using SABRE-SHEATH. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2015; 119:8786-8797. [PMID: 25960823 PMCID: PMC4419867 DOI: 10.1021/acs.jpcc.5b01799] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 03/28/2015] [Indexed: 05/14/2023]
Abstract
NMR signal amplification by reversible exchange (SABRE) is a NMR hyperpolarization technique that enables nuclear spin polarization enhancement of molecules via concurrent chemical exchange of a target substrate and parahydrogen (the source of spin order) on an iridium catalyst. Recently, we demonstrated that conducting SABRE in microtesla fields provided by a magnetic shield enables up to 10% 15N-polarization (Theis, T.; et al. J. Am. Chem. Soc.2015, 137, 1404). Hyperpolarization on 15N (and heteronuclei in general) may be advantageous because of the long-lived nature of the hyperpolarization on 15N relative to the short-lived hyperpolarization of protons conventionally hyperpolarized by SABRE, in addition to wider chemical shift dispersion and absence of background signal. Here we show that these unprecedented polarization levels enable 15N magnetic resonance imaging. We also present a theoretical model for the hyperpolarization transfer to heteronuclei, and detail key parameters that should be optimized for efficient 15N-hyperpolarization. The effects of parahydrogen pressure, flow rate, sample temperature, catalyst-to-substrate ratio, relaxation time (T1), and reversible oxygen quenching are studied on a test system of 15N-pyridine in methanol-d4. Moreover, we demonstrate the first proof-of-principle 13C-hyperpolarization using this method. This simple hyperpolarization scheme only requires access to parahydrogen and a magnetic shield, and it provides large enough signal gains to enable one of the first 15N images (2 × 2 mm2 resolution). Importantly, this method enables hyperpolarization of molecular sites with NMR T1 relaxation times suitable for biomedical imaging and spectroscopy.
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64
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Shi F, Coffey A, Waddell KW, Chekmenev EY, Goodson BM. Nanoscale Catalysts for NMR Signal Enhancement by Reversible Exchange. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2015; 119:7525-7533. [PMID: 26185545 PMCID: PMC4501382 DOI: 10.1021/acs.jpcc.5b02036] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 03/11/2015] [Indexed: 05/24/2023]
Abstract
Two types of nanoscale catalysts were created to explore NMR signal enhancement via reversible exchange (SABRE) at the interface between heterogeneous and homogeneous conditions. Nanoparticle and polymer comb variants were synthesized by covalently tethering Ir-based organometallic catalysts to support materials comprised of TiO2/PMAA (poly methacrylic acid) and PVP (polyvinyl pyridine), respectively, and characterized by AAS, NMR, and DLS. Following parahydrogen (pH2) gas delivery to mixtures containing one type of "nano-SABRE" catalyst particles, a target substrate, and ethanol, up to ~(-)40-fold and ~(-)7-fold 1H NMR signal enhancements were observed for pyridine substrates using the nanoparticle and polymer comb catalysts, respectively, following transfer to high field (9.4 T). These enhancements appear to result from intact particles and not from any catalyst molecules leaching from their supports; unlike the case with homogeneous SABRE catalysts, high-field (in situ) SABRE effects were generally not observed with the nanoscale catalysts. The potential for separation and reuse of such catalyst particles is also demonstrated. Taken together, these results support the potential utility of rational design at molecular, mesoscopic, and macroscopic/engineering levels for improving SABRE and HET-SABRE (heterogeneous-SABRE) for applications varying from fundamental studies of catalysis to biomedical imaging.
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65
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Nikolaou P, Goodson BM, Chekmenev EY. Inside Cover: NMR Hyperpolarization Techniques for Biomedicine (Chem. Eur. J. 8/2015). Chemistry 2015. [DOI: 10.1002/chem.201590031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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66
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Abstract
Recent developments in NMR hyperpolarization have enabled a wide array of new in vivo molecular imaging modalities, ranging from functional imaging of the lungs to metabolic imaging of cancer. This Concept article explores selected advances in methods for the preparation and use of hyperpolarized contrast agents, many of which are already at or near the phase of their clinical validation in patients.
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67
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Theis T, Truong M, Coffey AM, Shchepin R, Waddell KW, Shi F, Goodson BM, Warren WS, Chekmenev EY. Microtesla SABRE enables 10% nitrogen-15 nuclear spin polarization. J Am Chem Soc 2015; 137:1404-7. [PMID: 25583142 PMCID: PMC4333583 DOI: 10.1021/ja512242d] [Citation(s) in RCA: 256] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Indexed: 12/27/2022]
Abstract
Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to nitrogen-15 in pyridine and nicotinamide (vitamin B(3) amide) by conducting "signal amplification by reversible exchange" (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the (15)N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed "SABRE in shield enables alignment transfer to heteronuclei" or "SABRE-SHEATH", promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.
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68
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Barskiy DA, Kovtunov KV, Koptyug IV, He P, Groome KA, Best QA, Shi F, Goodson BM, Shchepin RV, Truong ML, Coffey AM, Waddell KW, Chekmenev EY. In situ and ex situ low-field NMR spectroscopy and MRI endowed by SABRE hyperpolarization. Chemphyschem 2014; 15:4100-7. [PMID: 25367202 PMCID: PMC4287267 DOI: 10.1002/cphc.201402607] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 09/26/2014] [Indexed: 12/11/2022]
Abstract
By using 5.75 and 47.5 mT nuclear magnetic resonance (NMR) spectroscopy, up to 10(5)-fold sensitivity enhancement through signal amplification by reversible exchange (SABRE) was enabled, and subsecond temporal resolution was used to monitor an exchange reaction that resulted in the buildup and decay of hyperpolarized species after parahydrogen bubbling. We demonstrated the high-resolution low-field proton magnetic resonance imaging (MRI) of pyridine in a 47.5 mT magnetic field endowed by SABRE. Molecular imaging (i.e. imaging of dilute hyperpolarized substances rather than the bulk medium) was conducted in two regimes: in situ real-time MRI of the reaction mixture (in which pyridine was hyperpolarized), and ex situ MRI (in which hyperpolarization decays) of the liquid hyperpolarized product. Low-field (milli-Tesla range, e.g. 5.75 and 47.5 mT used in this study) parahydrogen-enhanced NMR and MRI, which are free from the limitations of high-field magnetic resonance (including susceptibility-induced gradients of the static magnetic field at phase interfaces), potentially enables new imaging applications as well as differentiation of hyperpolarized chemical species on demand by exploiting spin manipulations with static and alternating magnetic fields.
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69
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Truong ML, Shi F, He P, Yuan B, Plunkett KN, Coffey AM, Shchepin RV, Barskiy DA, Kovtunov KV, Koptyug IV, Waddell KW, Goodson BM, Chekmenev EY. Irreversible catalyst activation enables hyperpolarization and water solubility for NMR signal amplification by reversible exchange. J Phys Chem B 2014; 118:13882-9. [PMID: 25372972 PMCID: PMC4259498 DOI: 10.1021/jp510825b] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Activation of a catalyst [IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD = cyclooctadiene)] for signal amplification by reversible exchange (SABRE) was monitored by in situ hyperpolarized proton NMR at 9.4 T. During the catalyst-activation process, the COD moiety undergoes hydrogenation that leads to its complete removal from the Ir complex. A transient hydride intermediate of the catalyst is observed via its hyperpolarized signatures, which could not be detected using conventional nonhyperpolarized solution NMR. SABRE enhancement of the pyridine substrate can be fully rendered only after removal of the COD moiety; failure to properly activate the catalyst in the presence of sufficient substrate can lead to irreversible deactivation consistent with oligomerization of the catalyst molecules. Following catalyst activation, results from selective RF-saturation studies support the hypothesis that substrate polarization at high field arises from nuclear cross-relaxation with hyperpolarized (1)H spins of the hydride/orthohydrogen spin bath. Importantly, the chemical changes that accompanied the catalyst's full activation were also found to endow the catalyst with water solubility, here used to demonstrate SABRE hyperpolarization of nicotinamide in water without the need for any organic cosolvent--paving the way to various biomedical applications of SABRE hyperpolarization methods.
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70
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Coffey AM, Kovtunov KV, Barskiy DA, Koptyug IV, Shchepin RV, Waddell KW, He P, Groome KA, Best QA, Shi F, Goodson BM, Chekmenev EY. High-resolution low-field molecular magnetic resonance imaging of hyperpolarized liquids. Anal Chem 2014; 86:9042-9. [PMID: 25162371 PMCID: PMC4165454 DOI: 10.1021/ac501638p] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We demonstrate the feasibility of microscale molecular imaging using hyperpolarized proton and carbon-13 MRI contrast media and low-field (47.5 mT) preclinical scale (38 mm i.d.) 2D magnetic resonance imaging (MRI). Hyperpolarized proton images with 94 × 94 μm(2) spatial resolution and hyperpolarized carbon-13 images with 250 × 250 μm(2) in-plane spatial resolution were recorded in 4-8 s (largely limited by the electronics response), surpassing the in-plane spatial resolution (i.e., pixel size) achievable with micro-positron emission tomography (PET). These hyperpolarized proton and (13)C images were recorded using large imaging matrices of up to 256 × 256 pixels and relatively large fields of view of up to 6.4 × 6.4 cm(2). (13)C images were recorded using hyperpolarized 1-(13)C-succinate-d2 (30 mM in water, %P(13C) = 25.8 ± 5.1% (when produced) and %P(13C) = 14.2 ± 0.7% (when imaged), T1 = 74 ± 3 s), and proton images were recorded using (1)H hyperpolarized pyridine (100 mM in methanol-d4, %P(H) = 0.1 ± 0.02% (when imaged), T1 = 11 ± 0.1 s). Both contrast agents were hyperpolarized using parahydrogen (>90% para-fraction) in an automated 5.75 mT parahydrogen induced polarization (PHIP) hyperpolarizer. A magnetized path was demonstrated for successful transportation of a (13)C hyperpolarized contrast agent (1-(13)C-succinate-d2, sensitive to fast depolarization when at the Earth's magnetic field) from the PHIP polarizer to the 47.5 mT low-field MRI. While future polarizing and low-field MRI hardware and imaging sequence developments can further improve the low-field detection sensitivity, the current results demonstrate that microscale molecular imaging in vivo is already feasible at low (<50 mT) fields and potentially at low (~1 mM) metabolite concentrations.
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71
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Nikolaou P, Coffey AM, Barlow MJ, Rosen MS, Goodson BM, Chekmenev EY. Temperature-ramped (129)Xe spin-exchange optical pumping. Anal Chem 2014; 86:8206-12. [PMID: 25008290 PMCID: PMC4139178 DOI: 10.1021/ac501537w] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2014] [Accepted: 06/26/2014] [Indexed: 12/12/2022]
Abstract
We describe temperature-ramped spin-exchange optical pumping (TR-SEOP) in an automated high-throughput batch-mode (129)Xe hyperpolarizer utilizing three key temperature regimes: (i) "hot"-where the (129)Xe hyperpolarization rate is maximal, (ii) "warm"-where the (129)Xe hyperpolarization approaches unity, and (iii) "cool"-where hyperpolarized (129)Xe gas is transferred into a Tedlar bag with low Rb content (<5 ng per ∼1 L dose) suitable for human imaging applications. Unlike with the conventional approach of batch-mode SEOP, here all three temperature regimes may be operated under continuous high-power (170 W) laser irradiation, and hyperpolarized (129)Xe gas is delivered without the need for a cryocollection step. The variable-temperature approach increased the SEOP rate by more than 2-fold compared to the constant-temperature polarization rate (e.g., giving effective values for the exponential buildup constant γSEOP of 62.5 ± 3.7 × 10(-3) min(-1) vs 29.9 ± 1.2 × 10(-3) min(-1)) while achieving nearly the same maximum %PXe value (88.0 ± 0.8% vs 90.1% ± 0.8%, for a 500 Torr (67 kPa) Xe cell loading-corresponding to nuclear magnetic resonance/magnetic resonance imaging (NMR/MRI) enhancements of ∼3.1 × 10(5) and ∼2.32 × 10(8) at the relevant fields for clinical imaging and HP (129)Xe production of 3 T and 4 mT, respectively); moreover, the intercycle "dead" time was also significantly decreased. The higher-throughput TR-SEOP approach can be implemented without sacrificing the level of (129)Xe hyperpolarization or the experimental stability for automation-making this approach beneficial for improving the overall (129)Xe production rate in clinical settings.
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72
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Shi F, Coffey AM, Waddell KW, Chekmenev EY, Goodson BM. Heterogeneous solution NMR signal amplification by reversible exchange. Angew Chem Int Ed Engl 2014; 53:7495-8. [PMID: 24889730 PMCID: PMC6284233 DOI: 10.1002/anie.201403135] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Indexed: 11/05/2022]
Abstract
A novel variant of an iridium-based organometallic catalyst was synthesized and used to enhance the NMR signals of pyridine in a heterogeneous phase by immobilization on polymer microbead solid supports. Upon administration of parahydrogen (pH2) gas to a methanol mixture containing the HET-SABRE catalyst particles and the pyridine, up to fivefold enhancements were observed in the (1)H NMR spectra after sample transfer to high field (9.4 T). Importantly, enhancements were not due to any residual catalyst molecules in solution, thus supporting the true heterogeneity of the SABRE process. Further significant improvements may be expected by systematic optimization of experimental parameters. Moreover, the heterogeneous catalyst is easy to separate and recycle, thus opening a door to future potential applications varying from spectroscopic studies of catalysis, to imaging metabolites in the body without concern of contamination from expensive and potentially toxic metal catalysts or accompanying organic molecules.
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Shi F, Coffey AM, Waddell KW, Chekmenev EY, Goodson BM. Heterogeneous Solution NMR Signal Amplification by Reversible Exchange. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201403135] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Nikolaou P, Coffey AM, Ranta K, Walkup LL, Gust BM, Barlow MJ, Rosen MS, Goodson BM, Chekmenev EY. Multidimensional mapping of spin-exchange optical pumping in clinical-scale batch-mode 129Xe hyperpolarizers. J Phys Chem B 2014; 118:4809-16. [PMID: 24731261 PMCID: PMC4055050 DOI: 10.1021/jp501493k] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
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We present a systematic, multiparameter
study of Rb/129Xe spin-exchange optical pumping (SEOP)
in the regimes of high xenon
pressure and photon flux using a 3D-printed, clinical-scale stopped-flow
hyperpolarizer. In situ NMR detection was used to study the dynamics
of 129Xe polarization as a function of SEOP-cell operating
temperature, photon flux, and xenon partial pressure to maximize 129Xe polarization (PXe). PXe values of 95 ± 9%, 73 ± 4%, 60
± 2%, 41 ± 1%, and 31 ± 1% at 275, 515, 1000, 1500,
and 2000 Torr Xe partial pressure were achieved. These PXe polarization values were separately validated by ejecting
the hyperpolarized 129Xe gas and performing low-field MRI
at 47.5 mT. It is shown that PXe in this
high-pressure regime can be increased beyond already record levels
with higher photon flux and better SEOP thermal management, as well
as optimization of the polarization dynamics, pointing the way to
further improvements in hyperpolarized 129Xe production
efficiency.
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Barskiy D, Kovtunov KV, Koptyug IV, He P, Groome KA, Best Q, Shi F, Goodson BM, Shchepin RV, Coffey AM, Waddell K, Chekmenev EY. The feasibility of formation and kinetics of NMR signal amplification by reversible exchange (SABRE) at high magnetic field (9.4 T). J Am Chem Soc 2014; 136:3322-5. [PMID: 24528143 PMCID: PMC3985893 DOI: 10.1021/ja501052p] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Indexed: 12/16/2022]
Abstract
(1)H NMR signal amplification by reversible exchange (SABRE) was observed for pyridine and pyridine-d5 at 9.4 T, a field that is orders of magnitude higher than what is typically utilized to achieve the conventional low-field SABRE effect. In addition to emissive peaks for the hydrogen spins at the ortho positions of the pyridine substrate (both free and bound to the metal center), absorptive signals are observed from hyperpolarized orthohydrogen and Ir-complex dihydride. Real-time kinetics studies show that the polarization build-up rates for these three species are in close agreement with their respective (1)H T1 relaxation rates at 9.4 T. The results suggest that the mechanism of the substrate polarization involves cross-relaxation with hyperpolarized species in a manner similar to the spin-polarization induced nuclear Overhauser effect. Experiments utilizing pyridine-d5 as the substrate exhibited larger enhancements as well as partial H/D exchange for the hydrogen atom in the ortho position of pyridine and concomitant formation of HD molecules. While the mechanism of polarization enhancement does not explicitly require chemical exchange of hydrogen atoms of parahydrogen and the substrate, the partial chemical modification of the substrate via hydrogen exchange means that SABRE under these conditions cannot rigorously be referred to as a non-hydrogenative parahydrogen induced polarization process.
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