Electron paramagnetic resonance studies of an active carbon: The influence of preparation procedure on the oxygen response of the linewidth

Boyer, Stephen J.; Clarkson, R. B.

doi:10.1016/0927-7757(93)02630-w

Cited by 46 publications

(40 citation statements)

References 6 publications

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“…140,173 The controlled production of these materials is very complex because the response of the paramagnetic centers to pO 2 is extremely sensitive to the conditions under which the charring takes place. 140,177,178 On the other hand, this has some beneficial aspects. For example, the range of sensitivity can be adapted to specific needs such as high sensitivity at low pO 2 or modest sensitivity over a very large range of pO 2 .…”

Section: Particulate Paramagnetic Materialsmentioning

confidence: 99%

Assessment of tumor oxygenation by electron paramagnetic resonance: principles and applications

2004

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This review paper attempts to provide an overview of the principles and techniques that are often termed electron paramagnetic resonance (EPR) oximetry. The paper discusses the potential of such methods and illustrates they have been successfully applied to measure oxygen tension, an essential parameter of the tumor microenvironment. To help the reader understand the motivation for carrying out these measurements, the importance of tumor hypoxia is first discussed: the basic issues of why a tumor is hypoxic, why these hypoxic microenvironments promote processes driving malignant progression and why hypoxia dramatically influences the response of tumors to cytotoxic treatments will be explained. The different methods that have been used to estimate the oxygenation in tumors will be reviewed. To introduce the basics of EPR oximetry, the specificity of in vivo EPR will be discussed by comparing this technique with NMR and MRI. The different types of paramagnetic oxygen sensors will be presented, as well as the methods for recording the information (EPR spectroscopy, EPR imaging, dynamic nuclear polarization). Several applications of EPR for characterizing tumor oxygenation will be illustrated, with a special emphasis on pharmacological interventions that modulate the tumor microenvironment. Finally, the challenges for transposing the method into the clinic will also be discussed.

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Section: Particulate Paramagnetic Materialsmentioning

confidence: 99%

Assessment of tumor oxygenation by electron paramagnetic resonance: principles and applications

2004

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“…4 Some non-invasive NMR methods have also been developed and used. These include 19 F NMR spectroscopy 5,6 and blood oxygen level-dependent (BOLD) imaging. 7,8 In addition, a highly sensitive and non-invasive measurement of oxygen can be achieved using EPR and Overhauser-based methods.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, several new paramagnetic particulate materials have been found to exhibit a pO 2 -dependent EPR linewidth: lithium phthalocyanine crystals, 13 lithium naphthalocyanine crystals, 14 natural charcoals such as fusinite 15 or gloxy, 16 analytical charcoals, 17,18 and synthetic carbohydrate chars. 19 Another type of particulate material that is particularly interesting can be found in India inks, which are suspensions of carbon black (CB) particles. The first EPR oximetry experiments in humans were in fact carried out using these inks.…”

Section: Introductionmentioning

confidence: 99%

Development and evaluation of biocompatible inks for the local measurement of oxygen using in vivo EPR

2004

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In vivo EPR oximetry is a powerful minimally invasive method that allows the measurement of oxygen in tissues through the use of a paramagnetic probe. In the present study, we investigated new strategies for preparing biocompatible inks containing carbon black particles (Printex U), which could be used as oxygen sensors. The carbon black particles were dispersed in solutions of biocompatible polymers of carboxy methyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC) or polyvinyl pyrrolidone (PVP). A total of 12 polymers with different molecular weights were tested. A physico-chemical characterization of the inks was carried out to assess the sedimentation of the particles, the rheological behavior of these inks, and the relative diffusion of the inks. The preparations with CMC and PVP had the highest viscosity and stability. The presence of the polymers did not modify the calibration curves (EPR linewidth as a function of the pO 2 ) of the carbon black. In vivo, the oxygen sensors were stable for at least one month in muscles as the EPR linewidth remained fully sensitive to induced ischemia or carbogen challenge. The calibration curve was not modified after this period of implantation. A first study of biocompatibility was carried out in vitro (hemolysis and cytotoxicity assay) and in vivo (histological examination). No sign of toxicity was observed using these inks. These preparations are good candidates for future in vivo studies including clinical trials.

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“…The EPR spectra of chars in water consisted of a single Lorenzian line with a peak-to-peak line width of about 0.5 G, and a typical free radical g-factor, close to the free electron value of 2.0023. Experimental details of char synthesis are described in [8].…”

Section: Samplesmentioning

confidence: 99%

Coal and Coal Constituent Studies by Advanced Emr Techniques

Belford¹,

Clarkson²

1997

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Advanced electronic magnetic resonance (EMR) methods are used to examine properties of coals, chars, and molecular species related to constituents of coal. During this grant period, progress was made on setting up a separate high frequency EMR system particularly appropriate for such studies and exploring the use of low-frequency dynamic nuclear polarization (DNP) to examine the interaction between fluids such as water and the surface of suspended char particles. W-band (100 Ghz) electronic magnetic resonance (EMR, EPR, or ESR) spectroscopy offers the extremely high resolution to discriminate among very similar chemical species that are constituents of coals and closely related materials such as chars and therefore to provide clues about chemical structures as well as an analytical tool. A W-band spectrometer exists in this laboratory, but as described in the proposal for this project, one of the first tasks was to set up another W-band station that would be particularly appropriate for study of such materials. This task has been progressing very well in the first six months of the project.This report focuses on a new and exciting EMR technique -very low frequency pulsed dynamic nuclear polarization spectroscopy -for the study of the interfaces between coal-like particles and the water medium in which they are suspended. Here is described the discovery by this technique of a transient chemical interaction between certain char particles and the hydrogen atoms of water molecules in the bulk.

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Electron paramagnetic resonance studies of an active carbon: The influence of preparation procedure on the oxygen response of the linewidth

Cited by 46 publications

References 6 publications

Assessment of tumor oxygenation by electron paramagnetic resonance: principles and applications

Assessment of tumor oxygenation by electron paramagnetic resonance: principles and applications

Development and evaluation of biocompatible inks for the local measurement of oxygen using in vivo EPR

Coal and Coal Constituent Studies by Advanced Emr Techniques

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