Adsorption of radon on silver exchanged zeolites at ambient temperatures.

Since more than 100 years, the adsorption of the radioactive noble gas radon (222Rn) is performed on activated charcoal at cryogenic temperatures. There is little-if any-progress in the field of radon adsorption at ambient conditions to facilitate the development of simple and compact radon adsorption systems. We report here on the truly remarkable property of the synthetic silver-exchanged zeolites Ag-ETS-10 and Ag-ZSM-5 to strongly adsorb radon gas at room temperature. 222Rn breakthrough experiments in nitrogen carrier gas have shown that these materials exhibit radon adsorption coefficients exceeding 3000 m3/kg at 293 K, more than two orders of magnitude larger than any noble gas adsorbent known to date. Water vapor and carrier gas type were found to strongly influence radon adsorption, practically qualifying these silver exchanged materials as a new class of radon adsorbents. Our results demonstrate that Ag-ETS-10 and Ag-ZSM-5 are materials that show high affinity towards radon gas at ambient temperatures making them candidate materials for environmental and industrial 222Rn mitigation applications. Adsorption systems based on silver loaded zeolites have the potential to replace activated charcoal as material of choice in many radon related research areas by avoiding the necessity of cryogenic cooling.

Characterization of COVID-19 outbreaks in three nursing homes during the first wave in Berlin, Germany.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) belongs to the coronavirus family and is characterized by its high transmission competence. Elderly COVID-19 patients are at significantly higher risk of severe course of disease and death. Therefore, outbreaks in nursing homes are particularly challenging for facility managers and health authorities. Here, we report three outbreaks of COVID-19 related to nursing homes (NH01.a, NH02 and NH03) with almost 1000 affected individuals during the first COVID-19 wave in Berlin, Germany. The occurrence of cases and the measures taken were analyzed retrospectively. In all three outbreaks, the index persons were nursing home employees or volunteers. Measures taken were quarantine of contacts, close-meshed tests, separation of the affected housing unit, suspension of admission, ban on visiting, and equipping staff with personal protective equipment, of which there was a shortage in Germany at the beginning of the pandemic. A court-ordered quarantine became necessary for three residents of NH01.a due to cognitive disabilities. In total, 61 persons were tested positive for SARS-CoV-2 in NH01.a, ten persons in NH02, and sixteen persons in NH03. Seventeen patients (27.9%) of NH01.a and three patients (18.8%) of NH03 were referred to hospital. Of all confirmed cases, thirteen (21.3%) related to NH01.a and four (25.0%) related to NH03 died as a result of the infection. Besides one 82 year old volunteer, all deceased persons were residents aged between 66 and 98. Our results emphasize the importance of a previously developed containment and cluster strategy for nursing homes. Due to the particular vulnerability of the residents, immediate action, close cooperation and communication between the facility management, residents, visitors and the health authorities are essential in the case of confirmed COVID-19 cases in healthcare facilities.

Therapeutic Efficacy of 213Bi-labeled sdAbs in a Preclinical Model of Ovarian Cancer.

Targeted alpha-particle therapy (TAT) might be a relevant therapeutic strategy to circumvent resistance to conventional therapies in the case of HER2-positive metastatic cancer. Single-domain antibody fragments (sdAb) are promising vehicles for TAT because of their excellent in vivo properties, high target affinity, and fast clearance kinetics. This study combines the cytotoxic α-particle emitter bismuth-213 (213Bi) and HER2-targeting sdAbs. The in vitro specificity, affinity, and cytotoxic potency of the radiolabeled complex were analyzed on HER2pos cells. Its in vivo biodistribution through serial dissections and via Cherenkov and micro-single-photon emission computed tomography (CT)/CT imaging was evaluated. Finally, the therapeutic efficacy and potential associated toxicity of [213Bi]Bi-DTPA-2Rs15d were evaluated in a HER2pos tumor model that manifests peritoneal metastasis. In vitro, [213Bi]Bi-DTPA-2Rs15d bound HER2pos cells in a HER2-specific way. In mice, high tumor uptake was reached already 15 min after injection, and extremely low uptake values were observed in normal tissues. Co-infusion of gelofusine resulted in a 2-fold reduction in kidney uptake. Administration of [213Bi]Bi-DTPA-2Rs15d alone and in combination with trastuzumab resulted in a significant increase in median survival. We describe for the very first time the successful labeling of an HER2-sdAb with the α-emitter 213Bi, and after intravenous administration, revealing high in vivo stability and specific accumulation in target tissue and resulting in an increased median survival of these mice especially in combination with trastuzumab. These results indicate the potential of [213Bi]Bi-DTPA-sdAb as a new radioconjugate for TAT, alone and as an add-on to trastuzumab for the treatment of HER2pos metastatic cancer.

Thorium-229 quantified in historical Thorium-228 capsules.

Thorium-229 is a valuable, but scarce, radionuclide for nuclear clock applications or targeted alpha therapy. While it is mostly produced by the decay of 233U, 229Th can also be produced by neutron irradiation of 226Ra. At SCK•CEN, capsules containing mainly 228Th (by-product of 226Ra irradiation) were characterized to quantify the present amounts of 229Th, 228Th, 227Ac, 226Ra with high resolution gamma spectroscopy, after a decay period of 40 years in which 228Th has decayed. High purity 229Th was quantified, and after recovery using radiochemical separation processes, it can be used to support ongoing research.