@article{mandzhieva_adelabu_nantogma_chekmenev_theis_2023, title={Delivering Robust Proton-Only Sensing of Hyperpolarized [1,2-<SUP>13</SUP>C<sub>2</sub>]-Pyruvate Using Broad-Spectral-Range Nuclear Magnetic Resonance Pulse Sequences}, volume={8}, ISSN={["2379-3694"]}, url={https://doi.org/10.1021/acssensors.3c01296}, DOI={10.1021/acssensors.3c01296}, abstractNote={Hyperpolarized [1-13C]pyruvate is the leading hyperpolarized injectable contrast agent and is currently under evaluation in clinical trials for molecular imaging of metabolic diseases, including cardiovascular disease and cancer. One aspect limiting broad scalability of the technique is that hyperpolarized 13C MRI requires specialized 13C hardware and software that are not generally available on clinical MRI scanners, which employ proton-only detection. Here, we present an approach that uses pulse sequences to transfer 13C hyperpolarization to methyl protons for detection of the 13C-13C pyruvate singlet, employing proton-only excitation and detection only. The new pulse sequences are robust to the B1 and B0 magnetic field inhomogeneities. The work focuses on singlet-to-magnetization (S2M) and rotor-synchronized (R) pulses, both relying on trains of hard pulses with broad spectral width coverage designed to effectively transform hyperpolarized 13C2-singlet hyperpolarization to 1H polarization on the CH3 group of [1,2-13C2]pyruvate. This approach may enable a broader adoption of hyperpolarized MRI as a molecular imaging technique.}, number={11}, journal={ACS SENSORS}, author={Mandzhieva, Iuliia and Adelabu, Isaiah and Nantogma, Shiraz and Chekmenev, Eduard Y. and Theis, Thomas}, year={2023}, month={Nov}, pages={4101–4110} }
 @article{browning_macculloch_tomhon_mandzhieva_chekmenev_goodson_lehmkuhl_theis_2023, title={Spin dynamics of [1,2-C-13(2)]pyruvate hyperpolarization by parahydrogen in reversible exchange at micro Tesla fields}, volume={25}, ISSN={["1463-9084"]}, url={https://doi.org/10.1039/D3CP00843F}, DOI={10.1039/d3cp00843f}, abstractNote={Hyperpolarization of 13C-pyruvate via Signal Amplificaton By Reversibble Exchange (SABRE) is an important recent discovery because of both the relative simplicity of hyperpolarization and the central biological relevance of pyruvate as a biomolecular probe for in vitro or in vivo studies. Here, we analyze the [1,2-13C2]pyruvate-SABRE spin system and its field dependence theoretically and experimentally. We provide first-principles analysis of the governing 4-spin dihydride-13C2 Hamiltonian and numerical spin dynamics simulations of the 7-spin dihydride-13C2-CH3 system. The analytical and the numerical results are compared to matching systematic experiments. With these methods we unravel the observed spin state mixing of singlet states and triplet states at microTesla fields and we also analyze the dynamics during transfer from micro-Tesla field to high field for detection to understand the resulting spectra from the [1,2-13C2]pyruvate-SABRE system.}, number={24}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Browning, Austin and Macculloch, Keilian and TomHon, Patrick and Mandzhieva, Iuliia and Chekmenev, Eduard Y. and Goodson, Boyd M. and Lehmkuhl, Soeren and Theis, Thomas}, year={2023}, month={Jun}, pages={16446–16458} }
 @article{nantogma_eriksson_adelabu_mandzhieva_browning_tomhon_warren_theis_goodson_chekmenev_2022, title={Interplay of Near-Zero-Field Dephasing, Rephasing, and Relaxation Dynamics and [1-C-13]Pyruvate Polarization Transfer Efficiency in Pulsed SABRE-SHEATH}, volume={11}, ISSN={["1520-5215"]}, url={https://doi.org/10.1021/acs.jpca.2c07150}, DOI={10.1021/acs.jpca.2c07150}, abstractNote={Hyperpolarized [1-13C]pyruvate is a revolutionary molecular probe enabling ultrafast metabolic MRI scans in 1 min. This technology is now under evaluation in over 30 clinical trials, which employ dissolution Dynamic Nuclear Polarization (d-DNP) to prepare a batch of the contrast agent; however, d-DNP technology is slow and expensive. The emerging SABRE-SHEATH hyperpolarization technique enables fast (under 1 min) and robust production of hyperpolarized [1-13C]pyruvate via simultaneous chemical exchange of parahydrogen and pyruvate on IrIMes hexacoordinate complexes. Here, we study the application of microtesla pulses to investigate their effect on C-13 polarization efficiency, compared to that of conventional SABRE-SHEATH employing a static field (∼0.4 μT), to provide the matching conditions of polarization transfer from parahydrogen-derived hydrides to the 13C-1 nucleus. Our results demonstrate that using square-microtesla pulses with optimized parameters can produce 13C-1 polarization levels of up to 14.8% (when detected, averaging over all resonances), corresponding to signal enhancement by over 122,000-fold at the clinically relevant field of 1.4 T. We anticipate that our results can be directly translated to other structurally similar biomolecules such as [1-13C]α-ketoglutarate and [1-13C]α-ketoisocaproate. Moreover, other more advanced pulse shapes can potentially further boost heteronuclear polarization attainable via pulsed SABRE-SHEATH.}, number={48}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Nantogma, Shiraz and Eriksson, Shannon L. and Adelabu, Isaiah and Mandzhieva, Iuliia and Browning, Austin and TomHon, Patrick and Warren, Warren S. and Theis, Thomas and Goodson, Boyd M. and Chekmenev, Eduard Y.}, year={2022}, month={Nov} }
 @article{mandzhieva_adelabu_chekmenev_theis_2022, title={Proton-Only Sensing of Hyperpolarized [1,2-C-13(2)]Pyruvate}, volume={11}, ISSN={["2379-3694"]}, url={https://doi.org/10.1021/acssensors.2c01608}, DOI={10.1021/acssensors.2c01608}, abstractNote={Hyperpolarized MRI is emerging as a next-generation molecular imaging modality that can detect metabolic transformations in real time deep inside tissue and organs. 13C-hyperpolarized pyruvate is the leading hyperpolarized contrast agent that can probe cellular energetics in real time. Currently, hyperpolarized MRI requires specialized "multinuclear" MRI scanners that have the ability to excite and detect 13C signals. The objective of this work is the development of an approach that works on conventional (i.e., proton-only) MRI systems while taking advantage of long-lived 13C hyperpolarization. The long-lived singlet state of [1,2-13C2]pyruvate is hyperpolarized with parahydrogen in reversible exchange, and subsequently, the polarization is transferred from the 13C2 spin pair to the methyl protons of pyruvate for detection. This polarization transfer is accomplished with spin-lock induced crossing pulses that are only applied to the methyl protons yet access the hyperpolarization stored in the 13C2 singlet state. Theory and first experimental demonstrations are provided for our method, which obviates 13C excitation and detection for proton sensing of 13C-hyperpolarized pyruvate with an overall experimental-polarization transfer efficiency of ∼22% versus a theoretically predicted polarization transfer efficiency of 25%.}, number={12}, journal={ACS SENSORS}, author={Mandzhieva, Iuliia and Adelabu, Isaiah and Chekmenev, Eduard Y. and Theis, Thomas}, year={2022}, month={Nov} }
 @article{brown_mandzhieva_tomhon_theis_castellano_2022, title={Triplet Photosensitized para-Hydrogen Induced Polarization}, volume={11}, ISSN={["2374-7951"]}, url={https://doi.org/10.1021/acscentsci.2c01003}, DOI={10.1021/acscentsci.2c01003}, abstractNote={Despite its enormous utility in structural characterization, nuclear magnetic resonance (NMR) spectroscopy is inherently limited by low spin polarization. One method to address the low polarization is para-hydrogen (p-H2) induced polarization (PHIP) which uses the singlet spin isomer of H2 to generate disparate nuclear spin populations to amplify the associated NMR signals. PHIP often relies on thermal catalysis or, more infrequently, UV-activated catalytic hydrogenation. Light-activated hydrogenation enables direct and timed control over the hyperpolarization of target substrates, critical for identifying short-lived intermediates. Here, we use an established Ir(III) triplet photosensitizer (PS) to visible light sensitize the triplet ligand-field states in the d6-transition metal dihydride Ru(CO)(PPh3)3(H)2 (1). Excitation inside a 9.4 T NMR spectrometer with the PS and a 420 nm blue LED, under 3 atm of p-H2, successfully photosensitized hyperpolarization in 1 and in a range of unsaturated substrates at and below room temperature, up to 1630-fold. In otherwise identical experimental conditions without light activation, no polarization was realized in 1 or the substrates evaluated. We believe triplet-sensitized PHIP (Trip-PHIP) represents a facile experimental means for probing triplet sensitized light activation in transition metal catalysts possessing low-lying triplet ligand-field states, providing mechanistic insight of potentially tremendous value in chemical catalysis.}, number={11}, journal={ACS CENTRAL SCIENCE}, author={Brown, Emily E. and Mandzhieva, Iuliia and TomHon, Patrick M. and Theis, Thomas and Castellano, Felix N.}, year={2022}, month={Nov} }
 @article{adelabu_tomhon_kabir_nantogma_abdulmojeed_mandzhieva_ettedgui_swenson_krishna_theis_et al._2021, title={Order-Unity C-13 Nuclear Polarization of [1-C-13]Pyruvate in Seconds and the Interplay of Water and SABRE Enhancement}, volume={11}, ISSN={["1439-7641"]}, url={https://doi.org/10.1002/cphc.202100839}, DOI={10.1002/cphc.202100839}, abstractNote={Signal Amplification By Reversible Exchange in SHield Enabled Alignment Transfer (SABRE-SHEATH) is investigated to achieve rapid hyperpolarization of  13C1 spins of [1-13C]pyruvate, using parahydrogen as the source of nuclear spin order. Pyruvate exchange with an iridium polarization transfer complex can be modulated via a sensitive interplay between temperature and co-ligation of DMSO and H2O. Order-unity 13C (>50%) polarization of catalyst-bound [1-13C]pyruvate is achieved in less than 30 s by restricting the chemical exchange of [1-13C]pyruvate at lower temperatures. On the catalyst bound pyruvate, 39% polarization are measured using 1.4 T NMR spectrometer, and extrapolated to >50% at the end of build-up in situ. The highest measured polarization of a 30-mM pyruvate sample, including free and bound pyruvate is 13% when using 20 mM DMSO and 0.5 M water in CD3OD. Efficient  13C polarization is also enabled by favorable relaxation dynamics in sub-microtesla magnetic fields, as indicated by fast polarization buildup rates compared to the T1 spin-relaxation rates ( e.g. , ~0.2 s-1 versus ~0.1 s-1, respectively, for a 6 mM catalyst-[1-13C]pyruvate sample). Finally, the catalyst-bound hyperpolarized [1-13C]pyruvate can be released rapidly by cycling the temperature and/or by optimizing the amount of water, paving the way to future biomedical applications of hyperpolarized [1-13C]pyruvate produced via comparatively fast and simple SABRE-SHEATH-based approaches.}, number={2}, journal={CHEMPHYSCHEM}, publisher={Wiley}, author={Adelabu, Isaiah and TomHon, Patrick and Kabir, Mohammad S. H. and Nantogma, Shiraz and Abdulmojeed, Mustapha and Mandzhieva, Iuliia and Ettedgui, Jessica and Swenson, Rolf E. and Krishna, Murali C. and Theis, Thomas and et al.}, year={2021}, month={Dec} }