Isotopic Carrier Research Articles

Inverse altitude effect disputes the theoretical foundation of stable isotope paleoaltimetry

Stable isotope paleoaltimetry that reconstructs paleoelevation requires stable isotope (δD or δ18O) values to follow the altitude effect. Some studies found that the δD or δ18O values of surface isotopic carriers in some regions increase with increasing altitude, which is defined as an “inverse altitude effect” (IAE). The IAE directly contradicts the basic theory of stable isotope paleoaltimetry. However, the causes of the IAE remain unclear. Here, we explore the mechanisms of the IAE from an atmospheric circulation perspective using δD in water vapor on a global scale. We find that two processes cause the IAE: (1) the supply of moisture with higher isotopic values from distant source regions, and (2) intense lateral mixing between the lower and mid-troposphere along the moisture transport pathway. Therefore, we caution that the influences of those two processes need careful consideration for different mountain uplift stages before using stable isotope palaeoaltimetry.

An Assessment of the Potential Use of BNNTs for Boron Neutron Capture Therapy.

Currently, nanostructured compounds have been standing out for their optical, mechanical, and chemical features and for the possibilities of manipulation and regulation of complex biological processes. One of these compounds is boron nitride nanotubes (BNNTs), which are a nanostructured material analog to carbon nanotubes, but formed of nitrogen and boron atoms. BNNTs present high thermal stability along with high chemical inertia. Among biological applications, its biocompatibility, cellular uptake, and functionalization potential can be highlighted, in addition to its eased utilization due to its nanometric size and tumor cell internalization. When it comes to new forms of therapy, we can draw attention to boron neutron capture therapy (BNCT), an experimental radiotherapy characterized by a boron-10 isotope carrier inside the target and a thermal neutron beam focused on it. The activation of the boron-10 atom by a neutron generates a lithium atom, a gamma ray, and an alpha particle, which can be used to destroy tumor tissues. The aim of this work was to use BNNTs as a boron-10 carrier for BNCT and to demonstrate its potential. The nanomaterial was characterized through XRD, FTIR, and SEM. The WST-8 assay was performed to confirm the cell viability of BNNTs. The cells treated with BNNTs were irradiated with the neutron beam of a Triga reactor, and the apoptosis caused by the activation of the BNNTs was measured with a calcein AM/propidium iodide test. The results demonstrate that this nanomaterial is a promising candidate for cancer therapy through BNCT.

Pretargeting: taking an alternate route for localizing radionuclides

Bispecific antibody pretargeting is a two-step procedure for selectively delivering radionuclides to tumors. The procedure was developed to solve a number of problems encountered when radionuclides are directly coupled to an IgG, such as slow blood clearance and delayed tumor accretion. While various forms of antibody fragments can reduce blood pool activity and provide faster tumor localization, tumor uptake is reduced considerably. In pretargeting procedures, the radionuclide is attached to a small molecule that quickly traverses the vascular barrier to reach the tumor cells, achieving maximum accretion within 0.5 to 1.0 h. Just as quickly, it is eliminated from the body, thereby minimizing tissue exposure and developing high tumor/tissue ratios very early. In order to capture the radionuclide in the tumor, a bispecific antibody (bsMAb) that binds to the tumor and to the isotope carrier (e.g., a hapten-peptide) is pre-administered some time earlier. The pretargeting procedure has been shown repeatedly to improve tumor localization as compared to directly radiolabeled antibodies, thereby enhancing both imaging and therapy. In this article, we review the progress our group has made toward developing and testing bsMAb pretargeting systems for cancer detection and therapy.

Measurement of P Contribution From Several P Sources by Using <sup>32</sup>P Method

P-fertilizer other than chemical fertilizers has been used extensively in agriculture. However, the extent to which P-fertilizer contributes to the growth of plants has only been discussed a few, meanwhile the information will be very helpful to the use of P-fertilizer efficiently. The 32 P method was used to distinguish P contribution from several sources, i.e soil, chemical fertilizer (Sp) and manure/organic fertilizer (Pk). The isotope carrier free solution of KH 2 32 PO 4 , which is contained of 98% 32 P, was applied to the soil and thus making it as the only source of labeled-P. Radioactivity counting of soil samples will lead to the measurement of P-contribution from several sources of P given. The experiment result showed that most of the P taken up by the plants was from soil. Thus, the P from Sp (P-Sp) and Pk (P-Pk) became un-significantly support the plant growth expressed in lesser dry weight of straw, grain and plants compared to those who taken its P from soil. Although soil contributed most of its available P to straw and grain of lowland rice, but Sp and Pk still contributed P to both plant parts. It was obtained that in straw 64 – 82% P was derived from soil; 12 – 21% P was derived from Pk; and 18 – 29% P was derived from Sp. For grain 49 – 89% P was derived from soil; 11 – 15% P was derived from Pk; and19 – 45% P was derived from Sp. Received: 20 November 2009; Revised: 09 August 2010; Accepted: 23 August 2010

PtRu-SiO<sub>2</sub>-TiO<sub>2</sub>/C Anode Electrocatalyst for Direct Methanol Fuel Cell

The PtRu-SiO2-TiO2/C anode electrocatalyst ( loading 10wt% PtRu ) of direct methanol fuel cell is prepared by the surface reductive deposition method, using Vulcan XC-72 carbon black coated with nanometer SiO2-TiO2 (SiO2-TiO2/C) as the isotopic carrier. The surface characteristics of nanometer SiO2-TiO2 is studied through nitrogen adsorption, which shows that it is of porous structure together with large surface area, that is benefit to enhance the activity of SiO2-TiO2 and the dispersion of PtRu nanoparticle on the carrier of SiO2-TiO2/C. X-ray diffraction( XRD ) and transmission electron microscopy( TEM ) are used to characterize the catalyst. The PtRu nanoparticle homodisperse in SiO2-TiO2/C carrier with diameter around 2.4 nm. Cyclic voltammograms and chronoamperograms are conducted to compare the electrochemical methanol oxidation activity of the PtRu-SiO2-TiO2/C catalyst with the commercial PuRu/C catalyst ( 20 wt% of PtRu ). The results show that PtRu-SiO2-TiO2/C has higher catalytic activity and anti-poisoning ability for methanol oxidation, the addition of porous SiO2-TiO2 can replace the PtRu to some extent, comparing with the commercial PuRu/C catalyst, not only the loading of PtRu has been cut down 50%, but also the electro-oxidizing activity of methanol improved. The electro-oxidizing mechanism is basically analyzed.

The determination of the rate of conjugation immunoglobuline with bifunctional chelator

The work was performed under the GACR project: „Technology of preparation of radionuclides and their labelled compounds for nuclear medicine and pharmacy with the use of the reactor LVR-15“ reg. no. 104/03/0499. Imaging of cell’s antigens with the use of labelled immunoglobulines allows imaging of specific receptors on cell membrane and specific tumours. It is necessary to carry out the labelling of the immunoglobulines with radionuclides of suitable physical properties, which form cations (e.g., 111In, 90Y, 177Lu) that form very strong chelates of sufficiently high stability constant preventing the dissociation of complexes or the radionuclide under “ in-vivo” conditions. The immunoglobuline must be conjugated with the bifunctional chelator (BCH), which contains both chelating unit and reactive group for binding to the immunoglobuline. In our laboratory we have conjugated human IgG and monoclonal antibody CD20 with diethylenetriamine pentaacetic acid dianhydride (cDTPAA). Radionuclides 90Y and 177Lu prepared on the LVR-15 reactor in NRI Rez were used for labelling. After conjugation and labelling the yields in relation to the amount of isotopic carrier have been determined.

A radiotracer technique for the migration of inorganic contaminants into dry food from packaging made from recycled paper and board

In nuclear and radiochemistry the concepts of specific activity, radioactive concentration, isotopic and non-isotopic carrier, carrier-free and no-carrier-added are of paramount relevance. In fact, traces of carrier are easily introduced in the radioactive preparations by their presence in the target material, by equipment and chemicals used in target processing, and may also be produced by side nuclear reactions induced in the target by nuclear activation, sometimes followed by a decay chain. Very sensitive analytical and radioanalytical techniques allow the determination of the real value of specific activity of no-carrier-added radionuclides and labeled compounds. Thus, in this paper we show with several examples that in most practical cases the term carrier-free (CF) is used improperly and has to be substituted by the more suitable term no-carrier-added (NCA). Carrier-free radionuclides and labeled compounds do exist in a few selected cases only.

Sorption Recovery of 137Cs and 90Sr with Carbonate-Containing Natural Mineral Tripolite

The sorption characteristics of a carbonate-containing mineral (tripolite) were studied on model aqueous solutions and real wastewaters in a wide range of pH in the presence of isotopic and nonisotopic carriers and organic impurities. The sorption of 137Cs and 90Sr is adequately described by a power function. Analysis of 137Cs sorption isotherms suggests that radiocesium is adsorbed by the ion-exchange mechanism, during which Cs+ ions from the solution exchange mainly with bivalent ions of the sorbent, whereas in 90Sr sorption trivalent ions of the sorbent also participate in the process. The saturation capacities of tripolite with respect to cesium and strontium were evaluated to be 0.3 and 1.0 mg-equiv g-1, respectively.

Thin-target excitation functions: a powerful tool for optimising yield, specific activity and radionuclidic purity of accelerator-produced radionuclides

In accelerator production of radionuclides, thin-target yield yEOIB(E) vs. projectile energy, at the end of an instantaneous bombardment (EOIB), is the slope at the “origin” of the growth curve of the activity of a radionuclide per unit beam current vs. irradiation time, for a target in which the energy loss is negligible in respect to projectile energy. Conversely, thick-target yield Y(E,ΔE) is a function of particle energy E (MeV) onto the target and energy loss ΔE (MeV) into target itself, obtained experimentally or by integration of thin-target excitation function y(E). Some local maxima on Y(E,ΔE) curves are present in many cases. As a relevant conclusion, use of target thickness larger than the “effective” value is unsuitable, due to larger specific power deposited by the beam in target material, instead of cooling system. Moreover, increasing amount of target material leads to a lower value of specific activity, due to larger amounts and volumes of chemicals and equipment. Y(E,ΔE) curves and their maxima permit calculating optimal irradiation conditions to produce radionuclides with maximum yield, specific activity and radionuclidic purity. In order to join the advantages of accurate knowledge of thin-target excitation functions, very selective radiochemical separations were optimised, without intentional addition of an isotopic carrier.

High resolution γ-spectrometry by HPGe detector and β-spectrometry by liquid scintillation counting, hyphenated to elemental analysis techniques: applications of high specific activity radio-nuclides for ultra-trace metallo-toxicological and environmental studies

Thin- and thick-target excitation functions of 188,189,191Pt radionuclides were experimentally determined by cyclotron irradiation, using nuclear reactions natOs(α,xn) in the energy range up to 38 MeV with the Scanditronix-MC40 Cyclotron of the Joint Research Centre-Ispra, VA (Italy) of the European Communities. Radionuclidic, radiochemical and chemical purities have been also measured by use of analytical and radioanalytical techniques. In this paper, the result of the experimental thick- and thin-target excitation functions of 188,189,191Pt radiotracers, produced via natOs(α,xn) reactions, are presented. The data are of relevant interest for optimising cyclotron production of platinum radionuclides to be used as radiotracers for metallo-biochemical, biomedical, toxicological and environmental studies. In this paper, we will present the analytical and radioanalytical methods that have been developed to determine the amount of isotopic carrier and the SA(NCA) in the case of 188Pt, 191Pt, to be used for ‘multiple labelling’ experiments, by: high resolution γ-spectrometry, β-spectrometry by liquid scintillation counting, neutron activation analysis, FL-AAS, and ICP-OES. Moreover, some preliminary biological applications were carried out in order to determine the cyto-toxicology of different chemical forms of platinum.

Evaluation of radioiodinated histamine as isotope carrier in vivo.

The iodo derivative of histamine labelled with 125I has been used for many years to prepare tracers used in RIA systems. The aim of this study was to evaluate radioiodinated histamine as a potential isotope carrier for in vivo applications. The biological behaviour of radioiodinated histamine has been investigated in rodents. The observed absence of any specific iodohistamine uptake by a critical organ or tissue promises a very quick distribution of the iodohistamine in soft tissues, and a rapid rate of whole-body clearance via the urinary tract (e.g. over 50% of the injected dose (ID) during the first hour after administration). In spite of moderately low in vitro stability of iodohistamine in serum, biodistribution studies in rodents have not shown any significant release of iodine from the parent molecule in the whole animal. Low uptake was observed in the thyroid (e.g. 0.22 and 0.11% ID at 1 and 2 h after administration to rats), and not more than 3% of injected activity was detected in the stomach in all of the biodistribution experiments. Moreover, our results refute any possibility of competition between histamine and iodohistamine for receptor binding sites, and suggest that radioactive mono-iodohistamine may be used successfully to develop some new radiolabelled bioactive molecules with potential application in vivo.

Analytical and radioanalytical quality control in high specific activity radiotracer preparation

High specific activity radiotracers, used in studies related to trace elements and human health, must be characterized by the following specific requirements: (i) high specific activity (activity/mass of isotopic carrier), (ii) high activity concentration (activity/volume or mass of substrate), (iii) radionuclidic, radiochemical and chemical purities, (iv) biological compatibility (physiological pH, sterility and physiological values). For this purpose, selective radiochemical separations and quality control procedures have been developed and tested at our laboratories for the production of several NCA radiotracers.

The gravimetric preparation of synthetic mixtures of iron isotopes

Five synthetic isotope mixtures were prepared with accurately known n( 54Fe)/ n( 56Fe) abundance ratios, by weighing and mixing two characterised compounds each enriched in one of the isotopes. These mixtures were used to calibrate isotope abundance measurements (using thermal ionization mass spectrometry) of a sample of natural iron. These measurements have led to a new calibrated value for the iron atomic weight [R. Maeck, Ph. D. Thesis, University Antwerpen (1992); P.D.P. Taylor, R. Maeck and P. De Bièvre, Int. J. Mass Spectrom. and Ion Processes, 121 (1992) 111]. The starting materials (Fe in the form of metal and 99.8% enriched, and Fe in the form of Fe 2O 3 and 99.9% enriched) were purified using semi-preparative ion chromatography, achieving minimal (< 5%) loss. Three consecutive separation schemes were used, and the purified materials were converted to Fe(NO 3) 3 and then transformed into α-Fe 2O 3 by heating to 950°C. This α-Fe 2O 3 was used as the isotope carrier compound for the weighings. It was a free flowing powder (particle size 1 μm) with an estimated level of impurities of 100 ± 1000 μg g −1 (2 s uncertainty) as obtained by spark source mass spectrometry. The stoichiometry and the uncertainty of the stoichiometry of the α-Fe 2O 3 were experimentally determined. The resulting five mixtures had n( 54Fe)/ n( 56Fe) isotope abundance ratios between the natural ratio (about 0.06370) and a ratio of 10. The relative uncertainty varied from two to 7 × 10 −4.

Determination of the absolute isotopic composition and Atomic Weight of a reference sample of natural iron

Absolute values have been obtained by means of thermal ionisation mass spectrometry for the iron isotope abundance ratios of a sample of metallic iron of natural isotopic composition. This was achieved by calibrating the mass spectrometric measurement procedure using five different synthetic isotope mixtures, prepared from carefully characterised enriched isotope carrier compounds, viz. 54Fe 2O 3 and 56Fe 2O 3. These mixtures were made up at three different n( 54Fe)/ n( 56Fe) ratios, covering a ratio range of more than two orders of magnitude, in order to determine the extent of the isotope fractionation in the ion source. Two mixtures bracket the natural ratio, two mixtures have ratio values approximating to unity, and one mixture has a ratio of about 10. The total relative uncertainty on the ratio values of the mixtures varies between 2 and 7 × 10 −4 (2 s). Three different mass spectrometric measurement procedures were developed, all using a silica-gel/boric acid ionisation enhancer. Measurements were carried out on two different instruments. The n( 54Fe)/ n( 56Fe) ratio of the synthetic mixtures and of the natural iron isotopic reference material (IRM) were measured using a mass spectrometer with Faraday detector. Both the n( 57Fe)/ n( 56Fe) and n( 58Fe)/ n( 56Fe) ratios of the natural iron IRM were determined using the same instrument but operated at a higher ionisation temperature (1430°C instead of 1350°C) and using an internal normalisation procedure. For the determination of the abundances of the minor isotopes in the enriched isotope carrier compounds, an instrument equipped with a calibrated ion counting device was used and the ionisation temperature was 1150°C. Using the latter instrument and method, the n( 54Fe)/ n( 56Fe) ratio of the IRM was found to a gree within 4 × 10 −5 with the calibrated value of the Faraday measurements, indicating that experimental conditions were well controlled in both cases. Compared to the current IUPAC data (Atomic Weights of the Elements, Pure Appl. Chem., 63 (1991) 975–990 and Isotopic Compositions of the Elements, Pure Appl. Chem., 63 (1991) 991-1002), which have not been changed since 1961 and which date back to uncalibrated measurements during the 1940s (G.E. Valley and H.H. Anderson, Phys. Rev., 59 (1941) 113; G.E. Valley and H.H. Anderson, J. Am. Chem. Soc., 69 (1947) 1871; J.R. White and A.E. Cameron, Phys. Rev., 74 (1948) 991), the uncertainties of the isotopic abundances obtained in this work have been improved by a factor of four to 15, and the Atomic Weight by a factor of six, even with a very conservative 2 s uncertainty estimate. Samples of this new IRM (CBNM IRM-014) are now available from CBNM.

Isotopic diversity in nebular dust: The distribution of Ti isotopic anomalies in carbonaceous chondrites

Average Ti isotopic patterns are derived for each class of carbonaceous chondrite from a chemically characterized suite of whole-rock samples. There is a well-resolved excess of 50Ti in a subset of CI meteorites. Mean values of the 50Ti excess for the four classes span a range of only 2 ϵ-units, with an apparent positive correlation with Al content. Previous evidence for anomalies in chrondrules ( Niemeyer, 1988) is augmented here by demonstrating that: 1) the more pristine Ca-Al-rich inclusions (CAIs) in Efremovka show the same isotopic pattern as the typical Allende CAI; and, 2) CM and CV matrix carry 50Ti excesses of about 2 ϵ-units. The Ti isotopic systematics in macroscopic constituents primarily reflect mixing of two isotopic components, even though at least four isotopic components were originally present. The nucleosynthetic origins and chemical fractionations of isotopic carriers are addressed by comparing relative magnitudes of the Fe-peak anomalies on an atom basis instead of ϵ-values. Thus, the statistical equilibrium and Si-burning origins are both still viable candidates for the 50Ti-rich component. An s-process component in Ti and Ca is also adduced from previously reported data for hibonite grains and two FUN CAIs. The distribution of Ti isotopic anomalies among matrix, chondrules, and CAIs suggests a model in which all three constituents formed from precursor-assemblages in which some chemical memories were still intact; the isotopic differences reflect fractionations among the carrier phases of the different isotopic components. Chondrules formed by a mostly closed-system melting of their precursors, and thus provide a recording of the extent of nebular heterogeneity on the mg-size scale. The larger anomalies in CAIs, compared to matrix and most (but not all) chondrules, are attributed primarily to an open- rather than closed-system processing of the CAI precursors. Precursors of both FUN and normal CAIs experienced an episode of intense processing, perhaps partial melting, that created the FUN characteristics, but for normal CAIs the FUN effects were erased by subsequent isotopic equilibration and exchange.

Extraction-chromatographic separation of137mBa from137Cs

The possibilities of extraction-chromatographic separation of137mBa from137Cs in genetic succession were studied, using columns filled with support beads loaded with the extractant H+[π)−(3)−1,2−B9C2H11]2Co−, further referred to as dicarbolide-H+, in nitrobenzene. The dependence of the amount of separable activities on experimental conditions was established. Optimal conditions were selected for the separation process. The effects of isotopic and nonisotopic carriers of137mBa on the separation and the degree on saturation of extraction-chromatographic column with Ba2+ ions were evaluated. The effects of acidity of the elution solutions, of flow-through velocity, the amount of elution solution and the quality of carrier beads on the separation process were assessed. The extraction-chromatographic yield was calculated and the number of possible repeated elution cycles for137mBa with saline and some other eluents was determined.

The influence of isotopic and nonisotopic carriers on the biodistribution and biokinetics of M3+-citrate complexes.

The influence of carrier amounts of Fe, Ga, and Tm on the biodistribution of 67Ga-, 59Fe-, and 167Tm-citrate in mice was investigated. Our results suggest that 167Tm, unlike 67Ga and 59Fe, is not transported by transferrin in the blood. Of the three radioisotopes tested, 167Tm had the highest tumor/background ratio (10 h after the injection). The application of Fe carrier led to an enhancement of the elimination of 67Ga from the blood and muscles, resulting in a better tumor/background ratio.

Enhancement of the Yu and Ledeen gas-liquid chromatographic method for sialic acid estimation: use of methane chemical ionization mass fragmentography

The sialic acid present in erythrocyte ghosts was estimated by methane chemical ionization mass fragmentography of the trimethylsilyl methyl glycosides. The internal standard was 3,4,6-tris-trimethylsilyl-alpha-phenyl-2-deoxy-2-acetamide-D-glucosaminide, as proposed by Yu and Ledeen (J. Lipid Res. 1970. 11: 506-516). The [MH-16]+ions (m/e 610 for the TMS-methylglycoside of N-acetylneuraminic acid and m/e 498 for the internal standard) were used for quantifying nanogram levels of sialic acid in the presence of other contaminating substances. This effectively raises the signal-to-noise ratio for the Yu and Ledeen method by at least two orders of magnitude. The sensitivity and linearity of the method, without use of isotopic carriers, were tested using known quantities of N-acetylneuraminic acid. The limit of detection was below 0.4 nanograms (approximately one picomole). The useful range of detection was 10 ng-1 microgram, showing a large dynamic range.

Isolation of137Cs from excreta by dicarbolide of cobalt

Extraction by polyhedral complex compound of the formula H+ [(π-(3)-1,2-B9C2H11)2Co−] further on referred to as dicarbolide-H+ and its chloro-derivate H+[B18C4H15Cl7Co−] further on referred to as Cl-dicarbolide-H+ in nitrobenzene was used for the analysis of137Cs in urine and faeces after internal contamination. The dependence of distribution ratio on the acidity of analysed solutions was determined. The effect of urine dilution was assessed as well as the effect of various concentrations of the extraction agents on the distribution ratio of137Cs. The effect of phase ratio at the different concentrations of isotopic carrier was assessed, as well as the effect of potassium ions on the decrease of the distribution ratio at the extraction of137Cs by dicarbolide-H+ or its chloro-derivate. The possibility of isolation of137Cs by extraction and the isolation of137Cs by ion-exchange absorbents and by ammonium molybdophosphate was compared. The values of distribution coefficient were determined at various concentrations of nitric acid and the isotopic carrier. The dependence of coextraction of some activated radionuclides and fission products by dicarbolide-H+ on the nitric acid concentration in the solute was determined. The effect of mass of contaminated faeces on the value of the distribution ratio of137Cs by the extraction was evaluated. As a result, a suggestion was given for the rutine isolation procedure of137Cs extraction with dicarbolide-H+ from the excreta contaminated by a mixture of radionuclides.

Mass Spectroscopic Studies on the Mechanism of Ionization of Atoms Formed as a Result of Radioactive Decay Processes. II

Measurements have been made on the charge states of ions produced by the electron capture decay of 109Cd(453d). The apparatus employed was a pulse-counting mode magnetic spectrometer, consisting an ion source chamber, an analyzer tube, a detector and 3-channel pumping systems. The radionuclide, 109Cd, produced by the nuclear reaction, 109Ag(d, 2n) 109Cd, was isolated without an isotopic carrier by the solvent extraction procedure developed by M. Inarida. A HCl solution of carrier-free 109Cd was dropped on the stainless steel meshes, which was later mounted to the ion source chamber. The ions produced by the electron capture decay of 109Cd on the solid surface were pulled out, analyzed by the magnetic field, and counted by a 16-stage Cu-Be electron multiplier. 109Cd decays to first excited state of 109Ag, which has a half life of 40 sec. Emitting 87.7 keV gamma rays, the state deexcites to the ground state of 109Ag. The gamma transition has an internal conversion coefficient larger than unity. The charge spectrum of the ions produced by the decay has shown that the most abundant species is singly-charged ions.