Performance and reproducibility of 13C and 15N hyperpolarization using a cryogen-free DNP polarizer

The setup, operational procedures and performance of a cryogen-free device for producing hyperpolarized contrast agents using dissolution dynamic nuclear polarization (dDNP) in a preclinical imaging center is described. The polarization was optimized using the solid-state, DNP-enhanced NMR signal to calibrate the sample position, microwave and NMR frequency and power and flip angle. The polarization of a standard formulation to yield ~ 4 mL, 60 mM 1-13C-pyruvic acid in an aqueous solution was quantified in five experiments to P(13C) = (38 ± 6) % (19 ± 1) s after dissolution. The mono-exponential time constant of the build-up of the solid-state polarization was quantified to (1032 ± 22) s. We achieved a duty cycle of 1.5 h that includes sample loading, monitoring the polarization build-up, dissolution and preparation for the next run. After injection of the contrast agent in vivo, pyruvate, pyruvate hydrate, lactate, and alanine were observed, by measuring metabolite maps. Based on this work sequence, hyperpolarized 15N urea was obtained (P(15N) = (5.6 ± 0.8) % (30 ± 3) s after dissolution)

How and Why Are Cancers Acidic? Carbonic Anhydrase IX and the Homeostatic Control of Tumour Extracellular pH.

The acidic tumour microenvironment is now recognized as a tumour phenotype that drives cancer somatic evolution and disease progression, causing cancer cells to become more invasive and to metastasise. This property of solid tumours reflects a complex interplay between cellular carbon metabolism and acid removal that is mediated by cell membrane carbonic anhydrases and various transport proteins, interstitial fluid buffering, and abnormal tumour-associated vessels. In the past two decades, a convergence of advances in the experimental and mathematical modelling of human cancers, as well as non-invasive pH-imaging techniques, has yielded new insights into the physiological mechanisms that govern tumour extracellular pH (pHe). In this review, we examine the mechanisms by which solid tumours maintain a low pHe, with a focus on carbonic anhydrase IX (CAIX), a cancer-associated cell surface enzyme. We also review the accumulating evidence that suggest a role for CAIX as a biological pH-stat by which solid tumours stabilize their pHe. Finally, we highlight the prospects for the clinical translation of CAIX-targeted therapies in oncology

Progress in low-field benchtop NMR spectroscopy in chemical and biochemical analysis

The employment of spectroscopically-resolved NMR techniques as analytical probes have previously been both prohibitively expensive and logistically challenging in view of the large sizes of high-field facilities. However, with recent advances in the miniaturisation of magnetic resonance technology, low-field, cryogen-free “benchtop” NMR instruments are seeing wider use. Indeed, these miniaturised spectrometers are utilised in areas ranging from food and agricultural analyses, through to human biofluid assays and disease monitoring. Therefore, it is both intrinsically timely and important to highlight current applications of this analytical strategy, and also provide an outlook for the future, where this approach may be applied to a wider range of analytical problems, both qualitatively and quantitatively

Cyclodextrin Chemistry and Toxicology

This is a reprint of the Special Issue "Cyclodextrin Chemistry and Toxicology”. This is a collection of eleven articles and three reviews that was published in Molecules that provides an overview of the applications of cyclodextrins, implements the information regarding the use of cyclodextrins and their inclusion complexes, considering both experimental and theorists approaches and using various scientific and technological tools

50th Rocky Mountain Conference on Analytical Chemistry

Final program, abstracts, and information about the 50th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Breckenridge, Colorado, July 27-31, 2008

Icp-Ms Analysis of Lanthanide-Doped Nanoparticles: A Quantitative and Multiplexing Approach to Investigate Biodistribution, Blood Clearance, and Targeting

The rapidly progressing field of nanotechnology promises to revolutionize healthcare in the 21st century, with applications in the prevention, diagnosis, and treatment of a wide range of diseases. However, before nanoparticulate agents can be brought into clinical use, they must first be developed, optimized, and evaluated in animal models. In the typical pre-clinical paradigm, almost all of the optimization is done at the in vitro level, with only a few select agents reaching the level of animal studies. Since only one experimental nanoparticle formulation can be investigated in a single animal, and in vivo experiments have relatively higher complexity, cost, and time requirements, it is not feasible to evaluate a very large number of agents at the in vivo stage. A major drawback of this approach, however, is that in vitro assays do not always accurately predict how a nanoparticle will perform in animal studies. Therefore, a method that allows many agents to be evaluated in a single animal subject would allow for much more efficient and predictive optimization of nanoparticles. We have found that by incorporating lanthanide tracer metals into nanoparticle formulations, we are successfully able to use inductively coupled plasma mass spectrometry (ICP-MS) to quantitatively determine a nanoparticle\u27s blood clearance kinetics, biodistribution, and tumor delivery. This approach was applied to evaluate both passive and active tumor targeting, as well as metabolically directed targeting of nanoparticles to low pH tumor microenvironments. Importantly, we found that these in vivo measurements could be made for many nanoparticle formulations simultaneously, in single animals, due to the high-order multiplexing capability of mass spectrometry. This approach allowed for efficient and reproducible comparison of performance between different nanoparticle formulations, by eliminating the effects of subject-to-subject variability. In the future, we envision that this higher-throughput evaluation of agents at the in vivo level, using ICP-MS multiplex analysis, will constitute a powerful tool to accelerate pre-clinical evaluation of nanoparticles in animal models

Detecting tumour responses to treatment using metabolic imaging with hyperpolarised [1-13C]pyruvate and 2-([18F]fluoro)-2-deoxy-D-glucose

Earlier detection of tumour responses to treatment would facilitate modification of treatment regimens and reduce unnecessary side effects and the costs of ineffective therapy. Anatomical changes following treatment are often slow to manifest and are occasionally misleading. Molecular imaging targeting dysregulated metabolic pathways in tumours can facilitate earlier detection of treatment response. The aim of this study was to directly compare two metabolic imaging techniques that measure different parts of glycolysis, 2-([18F]fluoro)-2-deoxy-D-glucose positron emission tomography ([18F]FDG-PET) and hyperpolarised [1-13C]pyruvate magnetic resonance imaging), for the purpose of detecting early responses to treatment in mouse models of cancer. Two mouse models of lymphoma, subcutaneous EL4 tumours and Eμ-Myc transgenic mice, were treated with etoposide and cyclophosphamide, respectively. In EL4 tumours 24 h after treatment there was a significant reduction in [18F]FDG uptake with no significant change in the hyperpolarised [1-13C]lactate/[1-13]Cpyruvate ratio. While treatment resulted in significant decreases in glucose transporter expression, there were variable amounts of cell death before and after treatment, potentially explaining this discrepancy. In Eμ-Myc mice, reductions of both [18F]FDG uptake and the [1-13C]lactate/[1-13C]pyruvate ratio were observed after treatment. However, the decreases in [18F]FDG uptake in cervical tumours were partially masked by high uptake in surrounding tissues demonstrating the benefit of improved specificity of hyperpolarised [1-13C]pyruvate for detecting the Warburg effect. In two xenograft models of human colorectal and breast adenocarcinoma, a large reduction in hyperpolarised [1-13C]lactate/[1-13C]pyruvate ratio was observed in all tumours 24 hours after treatment with a TRAIL agonist. However, despite treatment inducing widespread apoptosis and long-term remission, [18F]FDG-PET largely failed to detect a response. Measurements of [18F]FDG uptake in disaggregated tumour cells that had been sorted by fluorescence-activated cell sorting demonstrated that inflammatory infiltration or activation was not responsible for failure to detect a response to treatment with [18F]FDG. Furthermore, [1,6 13C2]glucose infusions into tumour bearing mice demonstrated that tumour uptake of [18F]FDG after treatment was not reflective of overall glycolytic flux.CRU

Hyperpolarized Carbon-13 Magnetic Resonance Imaging As A Tool For Assessing Lung Transplantation Outcomes

Lung transplantation is the established treatment for patients with chronic, end-stage lung diseases such as chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF) and cystic fibrosis (CF). However, its utility remains limited by the chronic shortage of donor lungs, limited lung preservation strategies and post-transplant complications leading to graft failure. Although efforts have been made to expand the limited pool of viable donor lungs via novel preservation strategies such as ex vivo lung perfusion (EVLP), our limited understanding of the mechanism and progression of donor lung injury continues to inhibit our ability to fully exploit these advances to improve lung transplant outcomes. Furthermore, the clinical standard for post-transplant assessment is limited to whole lung measurement such as pulmonary functional tests (PFTs) and structural imaging via radiography or HRCT, both of which lack the necessary sensitivity to detect lung rejection early. Given these limitations of currently available pre- and post-transplant lung assessment tools, a novel metabolic biomarker may provide higher sensitivity for determining the viability of donated lungs, as well as for assessing the onset of rejection before permanent structural changes in the lungs become apparent. We proposed that hyperpolarized (HP) [1-13C]pyruvate magnetic resonance imaging (MRI)—which provides real-time metabolic assessment of tissue based on the conversion of [1-13C] pyruvate to [1-13C]lactate via glycolysis, or to 13C bicarbonate via oxidative phosphorylation—may be an effective tool for assessing the health of donated lungs and may also serve as an early biomarker for detecting pulmonary graft dysfunction (PGD)-associated inflammation or acute lung rejection. In a rat model, we demonstrated the feasibility of using HP [1-13C]pyruvate nuclear magnetic resonance (NMR) spectroscopy to assess the viability of ex vivo perfused lungs. We further showed that our technique can be used to measure the improved viability of those lungs after treatment with ascorbic acid. Finally, translating our previously developed technique to in vivo HP [1-13C]pyruvate imaging of an inflamed rat lung, we not only demonstrated its utility for detecting lung transplantation rejection, but found that the HP lactate-to-pyruvate ratio is a better predictor of acute lung rejection in a rat model than computed tomography