Direct enhancement of nitrogen-15 targets at high-field by fast ADAPT-SABRE

Signal Amplification by Reversible Exchange (SABRE) is an attractive nuclear spin hyperpolarization technique capable of huge sensitivity enhancement in nuclear magnetic resonance (NMR) detection. The resonance condition of SABRE hyperpolarization depends on coherent spin mixing, which can be achieved naturally at a low magnetic field. The optimum transfer field to spin-1/2 heteronuclei is technically demanding, as it requires field strengths weaker than the earth's magnetic field for efficient spin mixing. In this paper, we illustrate an approach to achieve strong 15N SABRE hyperpolarization at high magnetic field by a radio frequency (RF) driven coherent transfer mechanism based on alternate pulsing and delay to achieve polarization transfer. The presented scheme is found to be highly robust and much faster than existing related methods, producing ∼3 orders of magnitude 15N signal enhancement within 2 s of RF pulsing

Efficacy and Safety of Human Retinal Progenitor Cells.

PURPOSE: We assessed the long-term efficacy and safety of human retinal progenitor cells (hRPC) using established rodent models. METHODS: Efficacy of hRPC was tested initially in Royal College of Surgeons (RCS) dystrophic rats immunosuppressed with cyclosporine/dexamethasone. Due to adverse effects of dexamethasone, this drug was omitted from a subsequent dose-ranging study, where different hRPC doses were tested for their ability to preserve visual function (measured by optokinetic head tracking) and retinal structure in RCS rats at 3 to 6 months after grafting. Safety of hRPC was assessed by subretinal transplantation into wild type (WT) rats and NIH-III nude mice, with analysis at 3 to 6 and 9 months after grafting, respectively. RESULTS: The optimal dose of hRPC for preserving visual function/retinal structure in dystrophic rats was 50,000 to 100,000 cells. Human retinal progenitor cells integrated/survived in dystrophic and WT rat retina up to 6 months after grafting and expressed nestin, vimentin, GFAP, and βIII tubulin. Vision and retinal structure remained normal in WT rats injected with hRPC and there was no evidence of tumors. A comparison between dexamethasone-treated and untreated dystrophic rats at 3 months after grafting revealed an unexpected reduction in the baseline visual acuity of dexamethasone-treated animals. CONCLUSIONS: Human retinal progenitor cells appear safe and efficacious in the preclinical models used here. TRANSLATIONAL RELEVANCE: Human retinal progenitor cells could be deployed during early stages of retinal degeneration or in regions of intact retina, without adverse effects on visual function. The ability of dexamethasone to reduce baseline visual acuity in RCS dystrophic rats has important implications for the interpretation of preclinical and clinical cell transplant studies

The Effect of Hypothermic and Cryogenic Preservation on Engineered Neural Tissue

This study explored different approaches to preserve Engineered Neural Tissue (EngNT), a stabilised cellular collagen hydrogel containing columns of aligned Schwann cells for nervous system repair. The ability to preserve EngNT without disrupting cellular and extracellular components and structures is important for clinical translation and commercialisation. Stabilised cellular gels and EngNT constructs were preserved under various conditions and cell survival assessed using live/dead microscopy and metabolic assay. Optimal survival was recorded in hypothermic (4ºC) conditions for 2-3 days using Hibernate®-A media, and, for longer term cryogenic storage (liquid nitrogen), using a mixture of 60% Dulbecco's Modified Eagle's Medium media (DMEM), 30% foetal calf serum (FCS) and 10% dimethyl sulfoxide (DMSO). Functionality and structure of preserved EngNT was assessed in co-culture with dorsal root ganglion (DRG) neurons, which indicated that alignment of Schwann cells and the ability of EngNT to support and guide neuronal regeneration were not disrupted. The identification of conditions that preserve EngNT will inform development of storage and transport methodologies to support clinical and commercial translation of this technology and other therapies based on cellular hydrogels

Optically Enhanced Solid-State ¹H NMR Spectroscopy

International audienceLow sensitivity is the primary limitation toextending nuclear magnetic resonance (NMR) techniques tomore advanced chemical and structural studies. Photochemicallyinduced dynamic nuclear polarization (photo-CIDNP) is an NMRhyperpolarization technique where light is used to excite a suitabledonor−acceptor system, creating a spin-correlated radical pairwhose evolution drives nuclear hyperpolarization. Systems thatexhibit photo-CIDNP in solids are not common, and this effecthas, up to now, only been observed for 13C and 15N nuclei.However, the low gyromagnetic ratio and natural abundance ofthese nuclei trap the local hyperpolarization in the vicinity of thechromophore and limit the utility for bulk hyperpolarization. Here,we report the first example of optically enhanced solid-state 1HNMR spectroscopy in the high-field regime. This is achieved viaphoto-CIDNP of a donor−chromophore−acceptor molecule in a frozen solution at 0.3 T and 85 K, where spontaneous spindiffusion among the abundant strongly coupled 1H nuclei relays polarization through the whole sample, yielding a 16-fold bulk 1Hsignal enhancement under continuous laser irradiation at 450 nm. These findings enable a new strategy for hyperpolarized NMRbeyond the current limits of conventional microwave-driven DNP

Long-lived States to Sustain SABRE Hyperpolarised Magnetisation

The applicability of the magnetic resonance (MR) technique in the liquid phase is limited by poor sensitivity and short nuclear spin coherence times which are insufficient for many potential applications. Here we illustrate how it is possible to address both of these issues simultaneously by harnessing long-lived hyperpolarised spin states that are formed by adapting the Signal Amplification by Reversible Exchange (SABRE) technique. We achieve more than 4 % net 1H-polarisation in a long-lived form that remains detectable for over ninety seconds by reference to proton pairs in the biologically important molecule nicotinamide and a pyrazine derivative whose in vivo imaging will offer a new route to probe disease in the futur

Sub-minute kinetics of human red cell fumarase: H-1 spin-echo NMR spectroscopy and C-13 rapid-dissolution dynamic nuclear polarization

Fumarate is an important probe of metabolism in hyperpolarized magnetic resonance imaging and spectroscopy. It is used to detect the release of fumarase in cancer tissues, which is associated with necrosis and drug treatment. Nevertheless, there are limited reports describing the detailed kinetic studies of this enzyme in various cells and tissues. Thus, we aimed to evaluate the sub-minute kinetics of human red blood cell fumarase using nuclear magnetic resonance (NMR) spectroscopy, and to provide a quantitative description of the enzyme that is relevant to the use of fumarate as a probe of cell rupture. The fumarase reaction was studied using time courses of H-1 spin-echo and C-13-NMR spectra. H-1-NMR experiments showed that the fumarase reaction in hemolysates is sufficiently rapid to make its kinetics amenable to study in a period of approximately 3 min, a timescale characteristic of hyperpolarized C-13-NMR spectroscopy. The rapid-dissolution dynamic nuclear polarization (RD-DNP) technique was used to hyperpolarize [1,4-C-13]fumarate, which was injected into concentrated hemolysates. The kinetic data were analyzed using recently developed FmR analysis and modeling of the enzymatic reaction using Michaelis-Menten equations. In RD-DNP experiments, the decline in the C-13-NMR signal from fumarate, and the concurrent rise and fall of that from malate, were captured with high spectral resolution and signal-to-noise ratio, which allowed the robust quantification of fumarase kinetics. The kinetic parameters obtained indicate the potential contribution of hemolysis to the overall rate of the fumarase reaction when C-13-NMR RD-DNP is used to detect necrosis in animal models of implanted tumors. The analytical procedures developed will be applicable to studies of other rapid enzymatic reactions using conventional and hyperpolarized substrate NMR spectroscopy.Cancer Research UK‐Engineering and Physical Sciences Research Council (CRUK/EPSRC) Imaging Centre in Cambridge and Manchester, Grant/Award Number: 16465; Cancer Research UK Programme, Grant/Award Number: 17242; European Research Council (ERC); Australian Research Council, Grant/Award Number: DP14010259

Doping and phase segregation in Mn2+- and Co2+-doped lead halide perovskites from Cs-133 and H-1 NMR relaxation enhancement

Lead halide perovskites belong to a broad class of compounds with appealing optoelectronic and photovoltaic properties. Doping with transition metal ions such as Mn2+ and Co2+ has recently been reported to substantially enhance luminescence and stability of these materials. However, so far atomic-level evidence for incorporation of the dopants into perovskite phases has been missing. Here, we introduce a general and straightforward method for confirming the substitutional doping of bulk perovskite phases with paramagnetic dopants. Using Cs-133 and H-1 solid-state MAS NMR relaxation measurements we provide for the first time direct evidence that, consistent with current understanding, Mn2+ is incorporated into the perovskite lattice of CsPbCl3 and CsPbBr3 and does not form clusters. We also show that, contrary to current conviction, Co2+ is not incorporated into the perovskite lattice of MAPbI(3)

Sub-minute kinetics of human red cell fumarase: 1 H spin-echo NMR spectroscopy and 13 C rapid-dissolution dynamic nuclear polarization.

Fumarate is an important probe of metabolism in hyperpolarized magnetic resonance imaging and spectroscopy. It is used to detect the release of fumarase in cancer tissues, which is associated with necrosis and drug treatment. Nevertheless, there are limited reports describing the detailed kinetic studies of this enzyme in various cells and tissues. Thus, we aimed to evaluate the sub-minute kinetics of human red blood cell fumarase using nuclear magnetic resonance (NMR) spectroscopy, and to provide a quantitative description of the enzyme that is relevant to the use of fumarate as a probe of cell rupture. The fumarase reaction was studied using time courses of 1 H spin-echo and 13 C-NMR spectra. 1 H-NMR experiments showed that the fumarase reaction in hemolysates is sufficiently rapid to make its kinetics amenable to study in a period of approximately 3 min, a timescale characteristic of hyperpolarized 13 C-NMR spectroscopy. The rapid-dissolution dynamic nuclear polarization (RD-DNP) technique was used to hyperpolarize [1,4-13 C]fumarate, which was injected into concentrated hemolysates. The kinetic data were analyzed using recently developed FmRα analysis and modeling of the enzymatic reaction using Michaelis-Menten equations. In RD-DNP experiments, the decline in the 13 C-NMR signal from fumarate, and the concurrent rise and fall of that from malate, were captured with high spectral resolution and signal-to-noise ratio, which allowed the robust quantification of fumarase kinetics. The kinetic parameters obtained indicate the potential contribution of hemolysis to the overall rate of the fumarase reaction when 13 C-NMR RD-DNP is used to detect necrosis in animal models of implanted tumors. The analytical procedures developed will be applicable to studies of other rapid enzymatic reactions using conventional and hyperpolarized substrate NMR spectroscopy