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Boron neutron capture therapy is a low-invasive cancer therapy based on the neutron fission process that occurs upon thermal neutron irradiation of 10B-containing compounds; this process causes the release of alpha particles that selectively damage cancer cells. Although several clinical studies involving mercaptoundecahydro-closo-dodecaborate and the boronophenylalanine–fructose complex are currently ongoing, the success of this promising anticancer therapy is hampered by the lack of appropriate drug delivery systems to selectively carry therapeutic concentrations of boron atoms to cancer tissues, allowing prolonged boron retention therein and avoiding the damage of healthy tissues. To achieve these goals, numerous research groups have explored the possibility to formulate nanoparticulate systems for boron delivery. In this review. we report the newest developments on boron vehiculating drug delivery systems based on nanoparticles, distinguished on the basis of the type of carrier used, with a specific focus on the formulation aspects. [ABSTRACT FROM AUTHOR]

The radiochemical effects of thermal neutron capture in tris(2,2,6,6-tetramethyl-3,5-heptandionato)chromium(III) (Cr(tmhd)3) were investigated. A method was devised to quantify the amount of the induced 51Cr activity recoverable in the original chemical form and to confirm that it is indeed Cr(tmhd)3. The method is based on a combination of chemical separation (column chromatography and recrystallization) and analytical (radio-TLC, HPLC, and gamma spectrometry) techniques. Cr(tmhd)3 samples were irradiated and purified in two steps after irradiation. We found that two of the (three) purification pathways yielded good agreement among final 51Cr activity concentrations. The corresponding samples appeared to be of exceptional radiochemical purity. [ABSTRACT FROM AUTHOR]

Boron neutron capture therapy is a low-invasive cancer therapy based on the neutron fission process that occurs upon thermal neutron irradiation of 10B-containing compounds; this process causes the release of alpha particles that selectively damage cancer cells. Although several clinical studies involving mercaptoundecahydro-closo-dodecaborate and the boronophenylalanine–fructose complex are currently ongoing, the success of this promising anticancer therapy is hampered by the lack of appropriate drug delivery systems to selectively carry therapeutic concentrations of boron atoms to cancer tissues, allowing prolonged boron retention therein and avoiding the damage of healthy tissues. To achieve these goals, numerous research groups have explored the possibility to formulate nanoparticulate systems for boron delivery. In this review. we report the newest developments on boron vehiculating drug delivery systems based on nanoparticles, distinguished on the basis of the type of carrier used, with a specific focus on the formulation aspects.

To observe the neutron transmutation and displacement damage effects, Au/n-Si/Ag Schottky barrier diodes were exposed to thermal neutron irradiation. Irradiation induced changes in Schottky barrier height, saturation current, and donor concentration were investigated by using current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the diodes. The irradiation for 10 s caused a little change in the Schottky diode parameters which were obtained from I-V and C-V measurements. Observable changes in the parameters occurred after the second irradiation of 30 s duration. After the total dose, an increase in saturation current and barrier height inhomogeneties took into place and a decrease in carrier concentration was observed due to the carrier removal effect of thermal neutron-induced damages. Whereas the values of zero bias barrier height have little change after irradiations, the values of ideality factor increased after irradiations. The values of zero-bias barrier height for all diodes was also calculated from reverse bias current characteristics. After second dose, the values of zero-bias barrier height decreased for all diodes. The values of series resistance were determined by Cheung functions before and after irradiations. Before irradiations, the values were found between 2.10 kΩ and 2.76 kΩ. After second dose, the values of series resistance of all diodes decreased and were found between 1.59 kΩ and 2.20 kΩ. Furthermore, the proof of thermal neutron transmutation of elements in the devices was given via energy dispersive spectroscopy (EDS) mapping. [ABSTRACT FROM AUTHOR]

Purpose: The efficacy of a boron-containing cholesteryl ester compound (BCH) as a boron neutron capture therapy (BNCT) agent for the targeted irradiation of PC-3 human prostate cancer cells was examined. Materials and methods: Liposome-based delivery of BCH was quantified with inductively coupled plasma-mass spectrometry (ICP-MS) and high-performance liquid chromatography (HPLC). Cytotoxicity of the BCH-containing liposomes was evaluated with neutral red, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-suIfophenyl)-2H-tetrazolium (MTS), and lactate dehydrogenase assays. Colony formation assays were utilized to evaluate the decrease in cell survival due to high-linear energy transfer (LET) particles resulting from 10 B thermal neutron capture. Results: BCH delivery by means of encapsulation in a lipid bilayer resulted in a boron uptake of 35.2 ±4.3 µg/109 cells, with minimal cytotoxic effects. PC-3 cells treated with BCH and exposed to a 9.4x1011 n/cm² thermal neutron fluence yielded a 20-25% decrease in clonogenic capacity. The decreased survival is attributed to the generation of high-LET α particles and 7Li nuclei that deposit energy in densely ionizing radiation tracks. Conclusion: Liposome-based delivery of BCH is capable of introducing sufficient boron to PC-3 cells for BNCT. High-LET α particles and 7Li nuclei generated from 10B thermal neutron capture significantly decrease colony formation ability in the targeted PC-3 cells. [ABSTRACT FROM AUTHOR]

Abstract: In order to assess internal doses from tritium at the JSNS (Japan Spallation Neutron Source), a correlation between the chemical forms of tritium generated in mercury and the amount of water in it was studied by simulating the generation of tritium in the mercury target used for a neutron source. The ratio of [3H]H2O to all of generated tritium increased with increase in the water concentration. An empirical equation to predict the content of [3H]H2O from the water concentration is proposed. [Copyright &y& Elsevier]

The effects of thermal neutron irradiation and excess oxygen on the properties of Ti-sheathed MgB2 wires were investigated separately in this paper. No significant influence was observed when thermal neutron irradiation with fluence levels of 1.23 x 1014 and 5.75 x 1014 cm2 were applied on the sample, while fluence level of 3.16 x 1015 cm2 provided a strong suppression of in-field critical current density. Excess oxygen in sample preparation process had negative effect on the properties of the MgB2 wires. The samples prepared in air possessed lower critical temperature and in-field current carrying capability in comparison with the sample prepared in glove box. [ABSTRACT FROM AUTHOR]

Abstract: Tritium generated in a mercury target is a source of potential exposure of personnel at high-energy accelerator facilities. Knowledge of the chemical form of tritium is necessary to estimate the internal doses. We studied the tritium generation upon thermal neutron irradiation of a mercury target modified into liquid lithium amalgam to examine the ratio of tritiated water ([3H]H2O) and tritiated hydrogen ([3H]H2). The ratio between [3H]H2O and [3H]H2 generated in lithium amalgam was 4:6 under these experimental conditions. [Copyright &y& Elsevier]

The internal structure of several alkali-borosilicate glasses has been studied when exposed to a high thermal neutron flux. More specifically, the different glasses we are interested in are widely used around the globe for neutron guide manufacturing and show drastically different resistance to irradiation. Samples were irradiated with the thermal flux from T4 experimental tube in ILL's High Flux Reactor up to a fluence of several 10 17 n/cm 2. The experimental tools employed for the structural analysis were Nuclear Magnetic Resonance (NMR) and Small Angle Neutron Scattering (SANS). NMR measurements allowed to detect the modification of atoms' close environment and these results have been correlated to evolutions at macroscopic scale. In addition, neutron scattering measurements have demonstrated the possibility to detect phase segregation in a zinc-alkali-borosilicate. [ABSTRACT FROM AUTHOR]

Abstract: Annihilation behaviors of irradiation defects induced by γ-ray in Li2TiO3 were studied by means of ESR and compared to those by thermal neutron. The ESR spectra indicated that E′- and O−-centers were formed after the γ-ray irradiation and isochronal annealing experiments showed that the amounts of E′- and O−-centers, which are Frenkel pair, decreased in the temperature range of 550–650K for the γ-ray irradiated sample, while for the thermal neutron irradiated one, those decreased in the lower temperature range of 400–500K. The activation energies of recombination reaction of E′-center and O−-center were 0.68±0.01 and 0.31±0.04eV for the γ-ray and the thermal neutron irradiated samples, respectively. In the γ-ray irradiated sample, the formation of defects is resulted from electron-excitations but that in thermal neutron irradiated one is mainly resulted from collision of energetic particles. Comparing with the γ-ray irradiated sample, it was found for the thermal neutron irradiated sample that O2 −-center would be easily formed and the recombination process of E′- and O2 −-centers would also take place. The processes of different defect formations like electron-excitation and collision processes, would produce the different defects such as O−- and O2 −-centers, leading to the different annihilation behaviors of irradiation defects. [ABSTRACT FROM AUTHOR]

Changes in the magnetic behavior of melt-textured Sm1.6Ba2.3Cu3.3Ox superconductor due to thermal neutron irradiation were investigated at 50 and 77 K. It was observed that Jc was enhanced up to five times in magnitude after a irradiation fluency of 1.476×1017 cm−2. We discuss which types of pinning centers can be responsible for the observed behavior. [Copyright &y& Elsevier]

Y1.6Ba2.3Cu3.3Ox superconductors with different amounts of boron doping have been synthesized using the MPMG technique. Undoped and boron-doped samples were irradiated with thermal neutrons to study the effect of defects produced by the fission reaction, B(n,α)Li, on the pinning and the critical current. We observed that the pinning and the critical current density were improved as a result of thermal neutron irradiation. This improvement was slightly stronger for the boron-doped samples compared to the undoped ones. [Copyright &y& Elsevier]