High-resolution Magic Angle Spinning Technique Research Articles

High‐resolution magic angle spinning 1H MRS in prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed malignancy in men worldwide, largely as a result of the increased use of the annual serum prostate‐specific antigen (PSA) screening test for detection. PSA screening has saved lives, but it has also resulted in the overtreatment of many patients with PCa because of a limited ability to accurately localize and characterize PCa lesions through imaging. High‐resolution magic angle spinning (HRMAS) 1H MRS has proven to be a strong potential clinical tool for PCa diagnosis and prognosis. The HRMAS technique allows valuable metabolic information to be obtained from ex vivo intact tissue samples and also enables the performance of histopathology on the same tissue specimens. Studies have found that the quantification of individual metabolite levels and metabolite ratios, as well as metabolomic profiles, shows strong potential to improve accuracy in PCa detection, diagnosis and monitoring. Ex vivo HRMAS is also a valuable tool for the interpretation of in vivo results, including the localization of tumors, and thus has the potential to improve in vivo diagnostic tests used in the clinic. Here, we primarily review publications of HRMAS 1H MRS and its use for the study of intact human prostate tissue. Copyright © 2013 John Wiley & Sons, Ltd.

Analyzing the effects of a single episode of neonatal maternal deprivation on metabolite profiles in rat brain: a proton nuclear magnetic resonance spectroscopy study

Animal models have greatly contributed to the understanding of neuropsychiatric disorders and have provided extensive evidence for the “neurodevelopmental hypothesis.” In this regard, a single and prolonged episode (24 h) of early maternal deprivation early in life, on postnatal day 9, has been proposed as an animal model for the investigation of certain neuropsychiatric disorders, including schizophrenia. Since metabolic changes in hippocampus (HIP) and prefrontal cortex (PFC) have been described among schizophrenic patients by using ex vivo high-resolution magic angle spinning (HR-MAS) proton ( 1H) nuclear magnetic resonance spectroscopy, in the present study we aimed to investigate the effects of maternal deprivation (MD) on the metabolite profiles of the developing brain by using the HR-MAS technique. MD significantly altered the hippocampal and cortical metabolic profile of neonatal rats (PND 13) in a sex-dependent manner. Glutamine and glutamate (Glx) and taurine of male and female rat pups were altered in both brain areas analyzed. Differences in hippocampal phosphorylethanolamine have also been found as a function of the MD protocol. In addition, MD induced some other region- and sex-dependent effects, including changes in N-acetyl aspartate and total choline signals in the hippocampi of male pups. Present findings indicate a different brain metabolic profile in our animal model of early life stress suggesting its potential utility in the implementation of translational neuropsychiatric research.

In vivo biodistribution and biological impact of injected carbon nanotubes using magnetic resonance techniques

Background:Single-walled carbon nanotubes (SWCNT) hold promise for applications as contrast agents and target delivery carriers in the field of nanomedicine. When administered in vivo, their biodistribution and pharmacological profile needs to be fully characterized. The tissue distribution of carbon nanotubes and their potential impact on metabolism depend on their shape, coating, and metallic impurities. Because standard radiolabeled or fluorescently-labeled pharmaceuticals are not well suited for long-term in vivo follow-up of carbon nanotubes, alternative methods are required.Methods:In this study, noninvasive in vivo magnetic resonance imaging (MRI) investigations combined with high-resolution magic angle spinning (HR-MAS), Raman spectroscopy, iron assays, and histological analysis ex vivo were proposed and applied to assess the biodistribution and biological impact of intravenously injected pristine (raw and purified) and functionalized SWCNT in a 2-week longitudinal study. Iron impurities allowed raw detection of SWCNT in vivo by susceptibility-weighted MRI.Results:A transitional accumulation in the spleen and liver was observed by MRI. Raman spectroscopy, iron assays, and histological findings confirmed the MRI readouts. Moreover, no acute toxicological effect on the liver metabolic profile was observed using the HR-MAS technique, as confirmed by quantitative real-time polymerase chain reaction analysis.Conclusion:This study illustrates the potential of noninvasive MRI protocols for longitudinal assessment of the biodistribution of SWCNT with associated intrinsic metal impurities. The same approach can be used for any other magnetically-labeled nanoparticles.

Ex-vivo HRMAS of adult brain tumours: metabolite quantification and assignment of tumour biomarkers

BackgroundHigh-resolution magic angle spinning (HRMAS) NMR spectroscopy allows detailed metabolic analysis of whole biopsy samples for investigating tumour biology and tumour classification. Accurate biochemical assignment of small molecule metabolites that are "NMR visible" will improve our interpretation of HRMAS data and the translation of NMR tumour biomarkers to in-vivo studies.Results1D and 2D 1H HRMAS NMR was used to determine that 29 small molecule metabolites, along with 8 macromolecule signals, account for the majority of the HRMAS spectrum of the main types of brain tumour (astrocytoma grade II, grade III gliomas, glioblastomas, metastases, meningiomas and also lymphomas). Differences in concentration of 20 of these metabolites were statistically significant between these brain tumour types. During the course of an extended 2D data acquisition the HRMAS technique itself affects sample analysis: glycine, glutathione and glycerophosphocholine all showed small concentration changes; analysis of the sample after HRMAS indicated structural damage that may affect subsequent histopathological analysis.ConclusionsA number of small molecule metabolites have been identified as potential biomarkers of tumour type that may enable development of more selective in-vivo 1H NMR acquisition methods for diagnosis and prognosis of brain tumours.

Quantification of amounts and 13C content of metabolites in brain tissue using high‐ resolution magic angle spinning 13C NMR spectroscopy

Metabolic pathway mapping using (13)C NMR spectroscopy has been used extensively to study interactions between neurons and glia in the brain. Established extraction procedures of brain tissue are time consuming and may result in degradation of labile substances. We examined the potential of mapping (13)C-enriched compounds in intact brain tissue using high-resolution magic angle spinning (HR-MAS) NMR spectroscopy. Sprague-Dawley rats received an intraperitoneal injection of [1,6-(13)C]glucose, and 15 min later the animals were subjected to microwave fixation of the brain. Quantification of concentration and (13)C labelling of metabolites in intact rat thalamus were carried out based on exogenous ethylene glycol concentrations measured from (1)H NMR spectra using an ERETIC (Electronic REference To access In vivo Concentrations) signal. The results from intact tissue were compared with those from perchloric acid-extracted brain tissue. Amounts of (13)C labelling at different positions (C2, C3 and C4) in glutamate, glutamine, gamma-aminobutyric acid and aspartate measured in either intact tissue or perchloric acid extracts were not significantly different. Proton NMR spectra were used for quantification of six different amino acids plus lactate, inositol, N-acetylaspartate, creatine and phosphocreatine. Again, results were very similar when comparing the methods. To our knowledge, this is the first time quantitative (13)C NMR spectroscopy measurements have been carried out on intact brain tissue ex vivo using the HR-MAS technique. The results show that HR-MAS (13)C NMR spectroscopy in combination with (1)H NMR spectroscopy and the ERETIC method is useful for metabolic studies of intact brain tissue ex vivo.

Resolving the Structure of Ligands Bound to the Surface of Superparamagnetic Iron Oxide Nanoparticles by High-Resolution Magic-Angle Spinning NMR Spectroscopy

A major challenge in magnetic nanoparticle synthesis and (bio)functionalization concerns the precise characterization of the nanoparticle surface ligands. We report the first analytical NMR investigation of organic ligands stably anchored on the surface of superparamagnetic nanoparticles (MNPs) through the development of a new experimental application of high-resolution magic-angle spinning (HRMAS). The conceptual advance here is that the HRMAS technique, already being used for MAS NMR analysis of gels and semisolid matrixes, enables the fine-structure-resolved characterization of even complex organic molecules bound to paramagnetic nanocrystals, such as nanosized iron oxides, by strongly decreasing the effects of paramagnetic disturbances. This method led to detail-rich, well-resolved (1)H NMR spectra, often with highly structured first-order couplings, essential in the interpretation of the data. This HRMAS application was first evaluated and optimized using simple ligands widely used as surfactants in MNP synthesis and conjugation. Next, the methodology was assessed through the structure determination of complex molecular architectures, such as those involved in MNP3 and MNP4. The comparison with conventional probes evidences that HRMAS makes it possible to work with considerably higher concentrations, thus avoiding the loss of structural information. Consistent 2D homonuclear (1)H- (1)H and (1)H- (13)C heteronuclear single-quantum coherence correlation spectra were also obtained, providing reliable elements on proton signal assignments and carbon characterization and opening the way to (13)C NMR determination. Notably, combining the experimental evidence from HRMAS (1)H NMR and diffusion-ordered spectroscopy performed on the hybrid nanoparticle dispersion confirmed that the ligands were tightly bound to the particle surface when they were dispersed in a ligand-free solvent, while they rapidly exchanged when an excess of free ligand was present in solution. In addition to HRMAS NMR, matrix-assisted laser desorption ionization time-of-flight MS analysis of modified MNPs proved very valuable in ligand mass identification, thus giving a sound support to NMR characterization achievements.

Proton high‐field NMR study of tomato juice

AbstractA detailed analysis of the proton high‐field (600 MHz) NMR spectra of tomato juice and pulp is reported for the first time. A combination of J‐resolved, COSY, TOCSY, DOSY, 1H–13C HSQC and 1H–13C HMBC 2D sequences was used to assign each spin system and to separate the components of the complex patterns in the 1D overlapped proton spectra. To obtain resolved proton spectra of tomato pulps the high‐resolution magic angle spinning technique was used; a comparison with the liquid‐state NMR spectra of the corresponding juices was accomplished. On the basis of the assignments made, the chemical composition of tomato juices from two cultivars (Red Setter and Ciliegino) was determined. Copyright © 2003 John Wiley & Sons, Ltd.