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Radiolabelling of industrially manufactured nanoparticles is useful for nanoparticle dosimetry in biodistribution or cellular uptake studies for hazard and risk assessment. Ideally for such purposes, any chemical processing post production should be avoided as it may change the physico-chemical characteristics of the industrially manufactured species. In many cases, proton irradiation of nanoparticles allows radiolabelling by transmutation of a tiny fraction of their constituent atoms into radionuclides. However, not all types of nanoparticles offer nuclear reactions leading to radionuclides with adequate radiotracer properties. We describe here a process whereby in such cases nanoparticles can be labelled with 7Be, which exhibits a physical half-life of 53.29 days and emits γ-rays of 478 keV energy, and is suitable for most radiotracer studies. 7Be is produced via the proton-induced nuclear reaction 7Li(p,n)7Be in a fine-grained lithium compound with which the nanoparticles are mixed. The high recoil energy of 7Be atoms gives them a range that allows the 7Be-recoils to be transferred from the lithium compound into the nanoparticles by recoil implantation. The nanoparticles can be recovered from the mixture by dissolving the lithium compound and subsequent filtration or centrifugation. The method has been applied to radiolabel industrially manufactured SiO2 nanoparticles. The process can be controlled in such a way that no alterations of the 7Be-labelled nanoparticles are detectable by dynamic light scattering, X-ray diffraction and electron microscopy. Moreover, cyclotrons with maximum proton energies of 17-18 MeV that are available in most medical research centres could be used for this purpose.
- Klíčová slova
- 7Be, Cyclotron, Lithium compounds, Nanomaterials, Nanoparticles, Proton irradiation, Radiolabelling, Recoil,
- Publikační typ
- časopisecké články MeSH
Nanoparticles of various materials were proposed as carriers of nuclides in targeted alpha particle therapy to at least partially eliminate the nuclear recoil effect causing the unwanted release of radioactive progeny originating in nuclear decay series of so-called in vivo generators. Here, we report on the study of 211Pb and 211Bi recoils release from the 223Ra surface-labelled TiO2 nanoparticles in the concentration range of 0.01-1 mg/mL using two phase separation methods different in their kinetics in order to test the ability of progeny resorption. We have found significant differences between the centrifugation and the dialysis used for labelled NPs separation as well as that the release of 211Pb and 211Bi from the nanoparticles also depends on the NPs dispersion concentration. These findings support our previously proposed recoils-retaining mechanism of the progeny by their resorption on the NPs surface. At the 24 h time-point, the highest overall released progeny fractions were observed using centrifugation (4.0% and 13.5% for 211Pb and 211Bi, respectively) at 0.01 mg/mL TiO2 concentration. The lowest overall released fractions at the 24 h time-point (1.5% and 2.5% for 211Pb and 211Bi respectively) were observed using dialysis at 1 mg/mL TiO2 concentration. Our findings also indicate that the in vitro stability tests of such radionuclide systems designed to retain recoil-progeny may end up with biased results and particular care needs to be given to in vitro stability test experimental setup to mimic in vivo dynamic conditions. On the other hand, controlled and well-defined progeny release may enhance the alpha-emitter radiation therapy of some tumours.
- Klíčová slova
- Bi-213, Bismuth, Pb-211, Ra-223, Radium, TiO2, lead, nanoparticles, nuclear recoil,
- Publikační typ
- časopisecké články MeSH
This review summarizes recent progress and developments as well as the most important pitfalls in targeted alpha-particle therapy, covering single alpha-particle emitters as well as in vivo alpha-particle generators. It discusses the production of radionuclides like 211At, 223Ra, 225Ac/213Bi, labelling and delivery employing various targeting vectors (small molecules, chelators for alpha-emitting nuclides and their biomolecular targets as well as nanocarriers), general radiopharmaceutical issues, preclinical studies, and clinical trials including the possibilities of therapy prognosis and follow-up imaging. Special attention is given to the nuclear recoil effect and its impacts on the possible use of alpha emitters for cancer treatment, proper dose estimation, and labelling chemistry. The most recent and important achievements in the development of alpha emitters carrying vectors for preclinical and clinical use are highlighted along with an outlook for future developments.
- Klíčová slova
- 223Ra, actinium, alpha particle, astatine, bismuth, decay, in vivo generators, nuclear recoil, radium, targeted alpha therapy,
- MeSH
- aktinium chemie terapeutické užití MeSH
- alfa částice terapeutické užití MeSH
- astat chemie terapeutické užití MeSH
- bismut chemie terapeutické užití MeSH
- chelátory chemie farmakokinetika MeSH
- dávka záření MeSH
- heterocyklické sloučeniny monocyklické chemie farmakokinetika MeSH
- heterocyklické sloučeniny chemie farmakokinetika MeSH
- knihovny malých molekul chemie farmakokinetika MeSH
- lidé MeSH
- nádory patologie radioterapie MeSH
- nosiče léků aplikace a dávkování chemie MeSH
- radiofarmaka chemie terapeutické užití MeSH
- radionuklidy chemie terapeutické užití MeSH
- radium chemie terapeutické užití MeSH
- vztah dávky záření a odpovědi MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
- Názvy látek
- 1,4,7-triazacyclononane-N,N',N''-triacetic acid MeSH Prohlížeč
- 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid MeSH Prohlížeč
- Actinium-225 MeSH Prohlížeč
- aktinium MeSH
- astat MeSH
- Astatine-211 MeSH Prohlížeč
- bismut MeSH
- Bismuth-213 MeSH Prohlížeč
- chelátory MeSH
- heterocyklické sloučeniny monocyklické MeSH
- heterocyklické sloučeniny MeSH
- knihovny malých molekul MeSH
- nosiče léků MeSH
- radiofarmaka MeSH
- radionuklidy MeSH
- Radium-223 MeSH Prohlížeč
- radium MeSH
BACKGROUND: Targeted alpha therapy is one of the most powerful therapeutical modalities available in nuclear medicine. It's therapeutic potency is based on the nuclides that emit one or several alpha particles providing strong and highly localized therapeutic effects. However, some of these radionuclides, like e.g.223Ra or 225Ac decay in cascades, where the radioactive progeny originating from the consecutive alpha-decays may leave the original vector and cause unwanted irradiation of non-target organs. This progeny, even if partially retained in target tissues by internalization processes, typically do not follow the fate of originally targeted radiopharmaceutical and potentially spread over body following their own biodistribution. In this study we aimed to estimate 211Pb/211Bi progeny fate from the 223Ra surface-labelled TiO2 nanoparticles in vitro and the fate of 211Pb in vivo in a mice model. RESULTS: In vitro stability studies have shown significant differences between the release of the mother 223Ra and its progeny (211Pb, 211Bi) in all the biological matrices that have been tested. The lowest released activities were measured in saline, resulting in less than 5 % of released activity for all nuclides. Contrary to that, the highest released activity of 223Ra of up to 10 % within 48 h was observed in 5 % solution of albumin. The released activity of its progeny; the 211Pb and 211Bi was in the range of 20-40 % in this test medium. Significantly higher released activities of 211Pb and 211Bi compared to 223Ra by at least 10 % was observed in each biological medium, except saline, where no significant differences were observed. The in vivo biodistribution studies results in a mice model, show similar pattern, where it was found that even after accumulation of nanoparticles in target tissues, approximately 10 % of 211Pb is continuously released into the blood stream within 24 h, followed by its natural accumulation in kidneys. CONCLUSION: This study confirms our assumption that the progeny formed in a chain alpha decay of a certain nuclide, in this case the 223Ra, can be released from its original vector, leave the target tissue, relocate and could be deposited in non-target organs. We did not observe complete progeny wash-out from its original target tissues in our model. This indicates strong dependence of the progeny hot atom fate after its release from the original radiopharmaceutical preparation on multiple factors, like their internalization and retention in cells, cell membranes, extracellular matrices, protein binding, etc. We hypothesize, that also the primary tumour or metastasis size, their metabolic activity may significantly influence progeny fate in vivo, directly impacting the dose delivered to non-target tissues and organs. Therefore a bottom-up approach should be followed and detailed pre-/clinical studies on the release and biodistribution of radioactive progeny originating from the chain alpha emitters should be preferably performed.
- Klíčová slova
- (211)Bi, (211)Pb, (223)Ra, Radioactive progeny, Recoil effect, Targeted alpha therapy,
- MeSH
- myši MeSH
- nanočástice * MeSH
- olovo MeSH
- radiofarmaka * terapeutické užití MeSH
- radionuklidy terapeutické užití MeSH
- tkáňová distribuce MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- olovo MeSH
- radiofarmaka * MeSH
- radionuklidy MeSH
New data are reported from the operation of a 2 liter C3F8 bubble chamber in the SNOLAB underground laboratory, with a total exposure of 211.5 kg days at four different energy thresholds below 10 keV. These data show that C3F8 provides excellent electron-recoil and alpha rejection capabilities at very low thresholds. The chamber exhibits an electron-recoil sensitivity of <3.5×10(-10) and an alpha rejection factor of >98.2%. These data also include the first observation of a dependence of acoustic signal on alpha energy. Twelve single nuclear recoil event candidates were observed during the run. The candidate events exhibit timing characteristics that are not consistent with the hypothesis of a uniform time distribution, and no evidence for a dark matter signal is claimed. These data provide the most sensitive direct detection constraints on WIMP-proton spin-dependent scattering to date, with significant sensitivity at low WIMP masses for spin-independent WIMP-nucleon scattering.
New results are reported from the operation of the PICO-60 dark matter detector, a bubble chamber filled with 52 kg of C_{3}F_{8} located in the SNOLAB underground laboratory. As in previous PICO bubble chambers, PICO-60 C_{3}F_{8} exhibits excellent electron recoil and alpha decay rejection, and the observed multiple-scattering neutron rate indicates a single-scatter neutron background of less than one event per month. A blind analysis of an efficiency-corrected 1167-kg day exposure at a 3.3-keV thermodynamic threshold reveals no single-scattering nuclear recoil candidates, consistent with the predicted background. These results set the most stringent direct-detection constraint to date on the weakly interacting massive particle (WIMP)-proton spin-dependent cross section at 3.4×10^{-41} cm^{2} for a 30-GeV c^{-2} WIMP, more than 1 order of magnitude improvement from previous PICO results.
- Publikační typ
- časopisecké články MeSH
The neutron spectrum was measured at two locations in the spent fuel storage facility of the Temelín nuclear power plant. The measurement had two primary objectives: to map the neutron -γ field by quantifying the ambient dose equivalent H∗(10) and to identify methods that could improve the quality of the adjusted neutron spectrum using a Bonner Sphere Spectrometer (BSS). Three spectrometers were used: a BSS and two proton recoil spectrometers. Hydrogen-filled proportional counters and an EJ309 scintillator were used to construct the a priori spectrum for BSS adjustment. The details of this process and its results are discussed. The a posteriori spectrum was used to calculate the ambient dose equivalent H∗(10). The resulting spectrum is highly thermalised, but the predominant contribution to H∗(10) was in the 100 keV-1.3 MeV range. The use of hydrogen-proportional counters in combination with the BSS is recommended.
- Klíčová slova
- Ambient dose equivalent, Digitizer, Gamma detector, Gamma spectra, Neutron detector, Neutron sources, Neutron spectra, Pulse shape discrimination, Unfolding,
- Publikační typ
- časopisecké články MeSH
For the past decade, researchers have been trying to understand the mechanism of the thermal reduction of graphite oxide. Because deuterium is widely used as a marker in various organic reactions, we wondered if deuterium-labeled graphite oxide could be the key to fully understand this mechanism. Graphite oxides were prepared by the Hofmann, Hummers, Staudenmaier, and Brodie methods, and a deuterium-labeled analogue was synthesized by the Hofmann method. All graphite oxides were analyzed not only using the traditional techniques but also by gas chromatography-mass spectrometry (GC-MS) during exfoliation in hydrogen and nitrogen atmospheres. GC-MS enabled us to compare differences between the chemical compositions of the organic exfoliation products formed during the thermal reduction of these graphite oxides. Nuclear analytical methods (Rutherford backscattering spectroscopy, elastic recoil detection analysis) were used to calculate the concentrations of light elements, including the ratio of hydrogen to deuterium. Combining all of these results we were able to determine graphite oxide's thermal reduction mechanism. Carbon dioxide, carbon monoxide, and water are formed from the thermal reduction of graphite oxide. This process is also accompanied by various radical reactions that lead to the formation of a large amount of carcinogenic volatile organic compounds, and this will have major safety implications for the mass production of graphene.
- Klíčová slova
- exfoliation, graphene, graphite oxide, isotope labeling, mechanism,
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The fast leakage neutron spectra have been measured on spherical nickel benchmark assembly of diameter 50 cm. The 252Cf neutron source with approximate emission of 5.0·108 n/s was placed into the centre of the sphere. Fast neutron spectrum in the range of 1-10 MeV was measured in the distance of 1 m from the sphere centre by means of proton recoil method using scintillation stilbene crystal. The experimental data were compared to transport calculations based on several evaluated nuclear data libraries using MCNP6. MCNP6 was compared with SCALE/MONACO program using the same ENDF/B-VII.1 library which leads to different differential neutron flux results. Best experimental agreement with calculation in MCNP6 is achieved with ENDF/B-VII.1 library. Contrary, worst agreement is achieved with JENDL-4.0 and CENDL-3.1 libraries. Furthermore, cross section sensitivity analysis for elastic and inelastic scattering for both main nickel isotopes (58Ni, 60Ni) was performed. It was shown that 58Ni isotope has higher influence on the result than 60Ni isotope in the entire energy range under study. The highest influence has the elastic XS of 58Ni around energy of 1.5 MeV. The inelastic cross section (XS) of 58Ni dominates in the energies above 2 MeV where two percent rise due to the inelastic XS leads up to 3.3% decrease in the neutron flux.
- Klíčová slova
- (252)Cf, fast neutron flux, MCNP6, SCALE, Spherical nickel benchmark, Stilbene detector,
- Publikační typ
- časopisecké články MeSH
