Search Results (4)

Background/Objectives: Terbium-161 is an interesting and promising theranostic radionuclide, thanks to its decay characteristics (T_1/2 = 6.95 d, E(β)_max = 593 keV, E(β)_av = 154 keV, E(γ) = 74.6 keV (10.2%)). Having similar chemical properties, it is considered as an alternative to currently used ¹⁷⁷Lu. In addition, ¹⁶¹Tb emits a significant amount of conversion and Auger electrons, which contribute to the enhancement of localised therapeutic effect. The aim of this paper is to describe the preparation of ¹⁶¹Tb in quantity and quality relevant for preclinical and early clinical studies and to provide practical notes on the preparation. Methods: No-carrier-added ¹⁶¹Tb has been repeatedly prepared by neutron irradiation of highly enriched ¹⁶⁰Gd targets (up to 98 mg of ¹⁶⁰Gd₂O₃) at nuclear reactor LVR-15 (CV Řež, Czech Republic) in four different irradiation positions. The separation and purification process of ¹⁶¹Tb from the bulk of ¹⁶⁰Gd target was performed by cation exchange chromatography with Dowex 50 W × 8 (H⁺ cycle, 200–400 mesh). Terbium-161 was obtained in ¹⁶¹TbCl₃ form and formulated into 0.1 M HCl solution. The γ-ray spectrometry was used for radionuclide identification and radionuclidic purity and the ICP-MS method for chemical purity measurements and specific activity determination. The DOTA labelling assay was performed, as described by Gracheva et al., providing an assessment of the apparent molar activity of the preparation in terms of its competitive interaction with stable daughter nuclide ¹⁶¹Dy. Results: Irradiations (59.2 h to 421.52 h) of enriched ¹⁶⁰Gd targets with mass ranging from 43.4 to 144.0 mg for ¹⁶⁰Gd(NO₃)₃ and from 12.5 to 98.3 mg for ¹⁶⁰Gd₂O₃ yielded 1.3–23.7 GBq of ¹⁶¹Tb. The separation yields of purified ¹⁶¹Tb varied from 85 to 99%, with the activities of 9.9–22.1 GBq and the highest achieved specific activity of the final product was 4.1 GBq/μg (of Tb). The DOTA chelator was radiolabelled with ¹⁶¹Tb at time points from 2 to 14 days after the end of separation (EOS). Conclusions: Based on our results, we describe practical aspects of terbium production at the laboratory scale with a particular focus on practical aspects and issues arising during the process that may surprise even experienced radiochemists, as lanthanoid separation is not always straightforward, even though it is well-known and has been extensively studied. The preparation of ¹⁶¹Tb in a n.c.a. form proceeds, according to the reported data, with high reproducibility and achieves significant activity levels suitable for both preclinical and clinical investigations by irradiation of highly enriched ¹⁶⁰Gd targets in LVR-15 reactor with subsequent separation and purification of ¹⁶¹Tb on cation exchange resin Dowex 50 W × 8(H⁺). The produced [¹⁶¹Tb]TbCl₃ is employed in subsequent experimental research and development for the labelling of preparations intended for preclinical applications. Full article

Background/Objectives: Radiotherapy is a widely applied first-line clinical treatment modality of cancer. Copper–cysteamine (Cu-Cy) nanoparticles represent a new type of photosensitizer that demonstrates significant anti-tumor potential by X-ray-induced photodynamic therapy. Iodide is a high-Z element with superior X-ray absorption ability and has the β-decay radiotherapeutic nuclide, ¹³¹I, which emits Cherenkov light. In this study we aimed to investigate the X-ray-induced photodynamic therapy potential of iodinated Cu-Cy (Cu-Cy-I) nanoparticles and also explore the local treatment efficacy of ¹³¹I-labeled Cu-Cy-I ([¹³¹I]Cu-Cy-I) nanoparticles. Methods: The synthesis of [¹³¹I]Cu-Cy-I nanoparticles was performed with [¹³¹I]I⁻ anions. The in vitro radiobiological effects on tumor cells incubated with Cu-Cy-I nanoparticles by X-ray irradiation were investigated. The in vivo tumor growth-inhibitory effects of the combination of Cu-Cy-I nanoparticles with X-ray radiotherapy and [¹³¹I]Cu-Cy-I nanoparticles were evaluated with 4T1 tumor-xenografted mice. Results: The in vitro experiment results indicated that the X-ray irradiation with the presence of Cu-Cy-I nanoparticles produced a higher intracellular reactive oxygen species (ROS) level and more DNA damage of 4T1 cells and showed a stronger tumor cell killing ability compared to X-ray irradiation alone. The in vivo experimental results with 4T1 breast carcinoma-bearing mice showed that the combination of an intratumoral injection of Cu-Cy-I nanoparticles and X-ray radiotherapy enhanced the tumor growth-inhibitory effect and prolonged the mice’s lives. Conclusions: Cu-Cy-I nanoparticles have good potential as new radiosensitizers to enhance the efficacy of external X-ray radiotherapy. However, the efficacy of local treatment with [¹³¹I]Cu-Cy-I nanoparticles at a low ¹³¹I dose was not verified. The effective synthesis of smaller sizes of nanoparticles is necessary for further investigation of the radiotherapy potential of [¹³¹I]Cu-Cy-I nanoparticles. Full article

Iron (Fe) is an essential trace element in plants; however, the available Fe in soil solution does not always satisfy the demand of plants. Genetic diversity in the rate of Fe uptake by plants has not been broadly surveyed among plant species or genotypes, although plants have developed various Fe acquisition mechanisms. The “live-autoradiography” technique with radioactive ⁵⁹Fe was adopted to directly evaluate the uptake rate of Fe by barley cultivars from a nutrient solution containing a very low concentration of Fe. The uptake rate of Fe measured by live autoradiography was consistent with the accumulation of Fe-containing proteins on the thylakoid membrane. The results revealed that the ability to acquire Fe from the low-Fe solution was not always the sole determinant of tolerance to Fe deficiency among barley genotypes. The live-autoradiography system visualizes the distribution of β-ray-emitting nuclides and has flexibility in the shape of the field of view. This technique will strongly support phenotyping with regard to the long-distance transport of nutrient elements in the plant body. Full article

The β⁺-emitting radionuclide ^86gY (t_1/2 = 14.7 h) forms a matched-pair with the β⁻-emitting therapeutic radionuclide ⁹⁰Y (t_1/2 = 2.7 d) for theranostic application in medicine. This approach demands a precise knowledge of the positron emission probability of the PET nuclide which was until recently rather uncertain for ^86gY. In this work, an ^86gY source of high radionuclidic purity was prepared and a direct measurement of the positron emission intensity per 100 decay of the parent (hereafter “positron emission intensity”) was performed using high-resolution HPGe detector γ-ray spectroscopy. The electron capture intensity was also determined as an additional check by measuring the K_α and K_β X-rays of energies 14.1 and 15.8 keV, respectively, using a low energy HPGe detector. From those measurements, normalized values of 27.2 ± 2.0% for β⁺-emission and 72.8 ± 2.0% for EC were obtained. These results are in excellent agreement with values recently reported in the literature based on a detailed decay scheme study. Full article