Search

This review describes the basic principles of radiometal-theranostics and its dawn based on the development of the positron-emitting 86Y and 86Y-labeled radiopharmaceuticals to quantify biodistribution and dosimetry of 90Y-labeled analogue therapeutics. The nuclear and inorganic development of 86Y (including nuclear and cross section data, irradiation, radiochemical separation and recovery) led to preclinical and clinical evaluation of 86Y-labeled citrate and EDTMP complexes and yielded organ radiation doses in terms of mGy/MBq 90Y. The approach was extended to [86/90Y]Y-DOTA-TOC, yielding again yielded organ radiation doses in terms of mGy/MBq 90Y. The review further discusses the consequences of this early development in terms of further radiometals that were used (68Ga, 177Lu etc.), more chelators that were developed, new biological targets that were addressed (SSTR, PSMA, FAP, etc.) and subsequent generations of radiometal-theranostics that resulted out of that. [ABSTRACT FROM AUTHOR]

Atmospheric radioxenon analyses conducted under the Comprehensive Test Ban Treaty Organization (CTBTO) necessitates the collection of air samples to quantify 135Xe, an indicator for nuclear explosions and reactor operations. Analytical instrument calibration for these analyses requires high quality, monoisotopic reference standards that are typically short lived, and therefore must be produced and shipped promptly to monitoring stations worldwide. The work described here outlines two methods to produce highly enriched 135Xe by irradiating stable monoisotopic targets by (1) neutron capture (n, ɣ) on monoisotopic 134Xe and (2) high energy photon irradiation (ɣ, n) of monoisotopic 136Xe. The targets were prepared by electromagnetic isotope separation of natural xenon. Results from each process were compared for 135Xe yield and purity. [ABSTRACT FROM AUTHOR]

Single and binary titanium and silicon xerogels were prepared to evaluate and compare their sorption performance with commercial sorbents (Al2O3 and TiO2) used for the 99Mo/99mTc separation, under neutral pH and room temperature conditions. Molybdenum sorption capacities were determined by batch equilibrium systems using Mo(VI) solutions labelled with 99Mo radiotracer. Ti-xerogel showed the highest 99Mo distribution coefficient and sorption capacity, while Si-xerogel exerted null affinity. Binary xerogels and reference sorbents showed similar capacities. Additionally, Ti-xerogel, after a heating process, drastically decreased its sorption capacity. Finally, a molybdenum sorption mechanism was studied. [ABSTRACT FROM AUTHOR]

Trace metal toxicology research aimed at generating human-relevant information for risk assessment requires the use of sensitive and sophisticated analytical techniques to determine typically µg kg−1 or lower concentrations of trace metals in tissues, cells, intracellular components of laboratory animals and humans. The results of these techniques are needed for an understanding of the biochemical mechanisms and bio-transformations involving trace metals. In this context, radioanalytical and nuclear methods plays a pivotal role. In order to give an idea of typical results which can be obtained by radioanalytical and nuclear techniques when used in combination with biochemical and molecular biology techniques of cellular fractionation we report here some typical studies carried out by means of non-carrier added radiotracers with high specific activity, and neutron activation analysis (NAA). The investigations have been performed in the context of an integrated and complementary in vivo and in vitro approach that uses both animal and human test systems. Applications reported concern: (1) the in vivo work on laboratory animals (brain regional thallium distribution in rats and identification of thallium binders in testis, by means of 201+202Tl); (2) in vitro investigations on cells of animal origin (arsenic uptake and biomethylation in rat brain aggregates, neurons, microglia and astrocytes as well as speciation of vanadate in Balb/3T3 cells, by means of 73As and 48V, respectively); (3) in vitro experiments on cell of human origin (intracellular behavior of cadmium in human umbilical cord blood stem cells, by means of 109Cd); (4) analytical determinations of trace metals in tissues of general population and patients potentially affected by metal-related disease, by means of NAA. The analytical determinations carried out allowed to relate total element concentrations in cells to the results of investigations at the intracellular and molecular levels with the goal of identifying the biochemical components that interact with trace metals. These findings demonstrate the great potential of radioanalytical and nuclear techniques in the context of an integrated in vivo-in vitro strategy adopted in trace metal toxicology research for a mechanistically-based hazard characterization concerning the exposure to low doses of trace metals. [ABSTRACT FROM AUTHOR]

The biological activity influence on the mangrove sediment capacity to remove 65Zn and 109Cd from tidal water was evaluated in a site chronically polluted. Benthic Activity Indexes (BAI), corresponding to relative estimates of biological impact on radiotracer accumulation, were higher for 109Cd (~ 38%) than for 65Zn (~ 10%) in the top centimetre of sediment. However, BAI exceeded 96% for deeper sediment layers. This apparent decrease in radiotracer diffusion into deep sediments through biological activity inhibition is stronger than reported for much less polluted mangrove nearby, suggesting that benthic organisms tolerant of chronic metal pollution may affect metal sorption mechanisms. [ABSTRACT FROM AUTHOR]

The aim of this study is to develop cerebral radiotracers for central nervous system receptors imaging. The synthesis, characterization and biological evaluation of two aryl piperazine Tc-radiocomplexes based on the piano stool motif [CpM(CO)] (Cp = cyclopentadienyl, M = Tc/Re) is reported. The Tc-radiocomplexes were obtained quickly (time < 5 min) with high radiochemical yields. The Tc-radiocomplexes characterized by high performance liquid chromatography comparison with the rhenium surrogates have both a suitable lipophilicity and are able to cross the blood brain barrier with 0.43 ± 0.05 and 1.96 ± 0.06% ID/g of brain uptake, at 10 min post injection. [ABSTRACT FROM AUTHOR]

Mangrove sediment cores sampled from Sepetiba Bay (SE Brazil) were covered with tidal water spiked with Se, Cr and Co to evaluate the removal efficiency of these radiotracers by underlying sediments. Variable time-evolution trends were observed along 115 h experiments, with significant differences between removal efficiencies of all radiotracers observed only after 70 h (Cr > Co > Se). After an event of Co release back to overlying water, there was a general trend of lower Co removal than observed for other radiotracers during the period from 20 to 54 h. After this event, alternated periods of higher Co and higher Se removal trends were observed, attributed to behavioural differences expected for such anionic and cationic radiotracers. While Se and Cr showed uniform time-evolution curves, as typically found in the literature for most radiotracers, Co removal rates presented oscillations, probably due to sensitivity to changes in redox conditions within underlying sediments. Results evidenced the role of mangrove sediments as trace element sinks, which have implications for coastal water quality and for possible uses of such sediments in wastewater treatment systems. [ABSTRACT FROM AUTHOR]

A study on the trace elements transfer from tidal water to mangrove sediments from Guanabara Bay (southeastern Brazil) was performed in laboratory microcosms. Sediment cores were covered with tidal water spiked with Cs, Mn and Co during 5-h experiments, and water samples were taken at regular intervals to measure uptake kinetics at the sediment-water interface. At the end of the experiments, the uptake and diffusional penetration into the sediments was evaluated. Half-removal times from water to sediments were slightly higher for Cs (3.4 ± 1.7 h) than observed for Mn (2.3 ± 0.2 h) and Co (2.6 ± 1.1 h). After these experiments, all radioisotopes presented decreasing activities with increasing sediment depth, being the distribution of Cs indicative of higher diffusion within the upper 2 cm. This study on the removal of Cs, Mn and Co from tidal water by mangrove sediments suggests that while Co and Mn presented closer behaviors, there was a slightly higher mobility of Cs. [ABSTRACT FROM AUTHOR]