International Journal of PIXE

Microcapsules that release antigen-capturing nanoparticles (AC-NPs) with macrophage inflammatory protein-3 alpha (MIP-3$\alpha$) and anti-programmed death-1 (PD-1) antibody are developed, and these microcapsules have the ability to enhance immunoresponses through cross-priming of cluster of differentiation 8+ (CD8+) T cells by dendritic cells (DCs) in vivo in BALB/c mice.

Lipid protamine hyaluronic acid nanoparticles containing AC-NPs generated via nanoprecipitation of 4 mg/mL of polylactic-co-glycolic acid (PLGA), 1,000 ng/mL of MIP-3$\alpha$ and 400 $\mu$g of anti-PD-1 were mixed with 1 mL of 4.0% alginate and 3.0% of hyaluronate and then sprayed with 0.5 mM of ferrous chloride. These capsules were injected subcutaneously around LM17 tumor in the left hind legs of BALB/c mice. The tumors were exposed to a radiation dose of 10 or 20 Gy from 100 keV soft X-ray radiation. PLGA AC-NPs and MIP-3$\alpha$ were released in response to the radiation dose.

PLGA AC-NPs captured tumor-derived protein antigens are released by exposure to radiation, and these antigens were transported to DCs that were recruited and activated by MIP-3$\alpha$, intensifying the DC-associated cross-priming of CD8+ T cells. These treatments resulted in increased antitumor effect and reduced metastasis by abscopal effect. Our targeted immunotherapy may lead to better tumor therapy.

This study conducted an evaluation of elemental composition of concrete in an old nuclear reactor facility using the particle-induced X-ray emission (PIXE) technique. Given that the physical volume of the concrete is huge, easy, and quick analysis of many samples via the PIXE method can expedite the decommissioning work. The result of this study confirmed that it is possible to use the PIXE method for detecting light and medium-heavy elements (from Na to Fe) in concrete without the complicated chemical treatment. Some of these elements contain parent nuclides of Na-24, Al-28, and Fe-55, which are dominant components with residual radioactivity for a period of up to 10 years after facility shutdown.

To understand the elemental characteristics of the exhaust particles from a jet aircraft, we performed an element analysis using an in-air PIXE system of the different lubrication oils of a jet engine (Mobil Jet Oil II, Mobil Jet Oil 254 and Eastman Turbo Oil 2380) and the jet fuel (JET A-1) to determine the effects on the exhaust particles. A high concentration (1,400–2,500 wt.-ppm) of P was detected from the analyzed three oil samples. The high concentration of P is probably due to the tricresyl phosphate (TCP: C${}_{21}$H${}_{21}$O₄P) contained in the oil samples. The S concentrations of the JET A-1 fuel samples with different collection dates were in the range of $<$10 to 530 wt.-ppm. These results aid in determining the component features of nanoparticles emitted from an aircraft.

We explored whether medical positron emission tomography (PET) cyclotron proton beams could be used for proton-induced X-ray emission (PIXE) analysis. The beam current of the medical PET cyclotron is high, as required for radioisotope production, and is not commonly used for PIXE analysis. We successfully extracted stable proton beams of low intensity by using the ion source of a medical cyclotron to exploit proton impurities in deuteron gas. We performed 20-MeV PIXE analysis of a biological sample (used tea leaves). Elements lighter than Sr could be detected with high sensitivity ($<$14 ppm) using a silicon drift detector. We thus showed that a medical cyclotron widely used for PET diagnosis could be employed for PIXE analysis of biological samples.

We performed a particle-induced X-ray emission (PIXE) analysis of tea leaf samples (Camellia sinensis (L.) Kuntze) to evaluate the possibility of internal radiation exposure due to the intake of green tea contaminated with ${}^{134,137}$Cs and ${}^{90}$Sr. The tea leaf samples were obtained from tea trees (Camellia sinensis cv. ‘Yabukita’) cultivated with stable Cs and Sr added to the soil. We prepared the used leaf samples which were placed in distilled hot water (90${}^{\circ }$ for 1 min) as well as the unused leaf samples. The results of PIXE analysis combined with the internal standard method using Indium as a standard element showed little elution of Ca and Sr from the leaves to green tea, while the concentration of alkali elements, including Cs in the leaf, decreased by 30–40% after the tea was extracted.

We investigated the relationships between the element concentrations in blood and hair to clarify the sex-specific differences in elemental movement from blood to hair, as we confirmed the presence of large sex-specific differences in the concentrations of certain elements in hair in our previous study. First, we compared the elemental concentrations in serum/plasma taken from healthy people ($n=148$ females, 142 males) and found that there were significant differences (up to 20%) between females and males in levels of phosphorus, sulfur, calcium, bromine, and lead. We then examined the sex-specific differences in the elemental transfer factors from blood to hair by analyzing plasma and hair samples that had been simultaneously collected from the same people (20 females, 21 males). Calcium and selenium showed significant differences in transfer factors from plasma to hair. Particularly, large sex-specific differences in the calcium concentration were explained by the difference in the transfer factors from blood to hair. We also examined the sex-specific differences among teenaged subjects alone ($n=47$ females, 9 males; average age was approximately 17 years old) and noted no significant difference in the transfer factors between sexes. Taken together, these findings indicate that the transfer factors themselves are influenced by the excretion of sex hormones.