RESUMEN
Targeted Radionuclide Therapies (TRTs) based on Auger emitting radionuclides have the potential to deliver extremely selective therapeutic payloads on the cellular level. However, to fully exploit this potential, suitable radionuclides need to be applied in combination with appropriate delivery systems. In this review, we summarize the state-of-the-art production, purification, chelation and applications of two promising candidates for Targeted Auger Therapy, namely antimony- 119 (119Sb) and mercury-197 (197Hg). Both radionuclides have great potential to become efficient tools for TRT. We also highlight our current progress on the production of both radionuclides at TRIUMF and the University of Wisconsin.
Asunto(s)
Antimonio/farmacología , Radioisótopos de Mercurio/farmacología , Radioquímica/métodos , Radioisótopos/farmacología , Radiofármacos/farmacología , Antimonio/química , Electrones , Radioisótopos de Mercurio/química , Radioisótopos/química , Radiofármacos/síntesis químicaRESUMEN
Methylmercury (MeHg) is known to biomagnify in marine food chains, resulting in higher concentrations in upper trophic level animals than their prey. To better understand how marine copepods, an important intermediate between phytoplankton and forage fish at the bottom of the food chain, assimilate and release MeHg, the authors performed a series of laboratory experiments using the gamma-emitting radiotracer 203 Hg2+ and Me203 Hg with the calanoid copepod Acartia tonsa. Assimilation efficiencies of Hg2+ and MeHg ranged from 25% to 31% and 58% to 79%, respectively, depending on algal diets. Assimilation efficiencies were positively related to the fraction of Hg in the cytoplasm of the algal cells that comprised their diet. Efflux rates of Hg2+ (0.29/d) and MeHg (0.21/d) following aqueous uptake were similar, but efflux rates following dietary uptake were significantly lower for MeHg (0.11-0.22/d) than Hg2+ (0.47-0.66/d). The calculated trophic transfer factors in copepods were >1 for MeHg and consistently low (≤0.2) for Hg2+ . The authors used the parameters measured to quantitatively model the relative importance of MeHg sources (water or diet) for copepods and to predict the overall MeHg concentrations in copepods in different marine environments. In general, MeHg uptake from the diet accounted for most of the body burden in copepods (>50%). For an algal diet with a MeHg dry weight bioconcentration factor ≥106 , >90% of a copepod's MeHg body burden can be shown to derive from the diet. The model-predicted MeHg concentrations in the copepods were comparable to independent measurements for copepods in coastal and open-ocean regions, implying that the measured parameters and model are applicable to natural waters. Environ Toxicol Chem 2017;36:1287-1293. © 2016 SETAC.
Asunto(s)
Copépodos/química , Compuestos de Metilmercurio/análisis , Contaminantes Químicos del Agua/análisis , Animales , Carga Corporal (Radioterapia) , Copépodos/metabolismo , Criptófitas/metabolismo , Cadena Alimentaria , Iones/química , Mercurio/análisis , Mercurio/metabolismo , Radioisótopos de Mercurio/química , Compuestos de Metilmercurio/metabolismo , Compuestos de Metilmercurio/toxicidad , Fitoplancton/química , Fitoplancton/metabolismo , Contaminantes Químicos del Agua/metabolismoRESUMEN
Mercury is a toxic compound that can contaminate humans through food and especially via fish consumption. Mercury's toxicity depends on the species, with methylmercury being the most hazardous form for humans. Hg speciation analysis has been and remains a widely studied subject because of the potential difficulty of preserving the initial distribution of mercury species in the analysed sample. Accordingly, many analytical methods have been developed and most of them incur significant loss and/or cross-species transformations during sample preparation. Therefore, to monitor and correct artefact formations, quantification by isotope dilution is increasingly used and provides significant added value for analytical quality assurance and quality control. This review presents and discusses the two different modes of application of isotope dilution analysis for elemental speciation (i.e. species-unspecific isotope dilution analysis and species-specific isotope dilution analysis) and the different quantification techniques (i.e. classical and multiple spike isotope dilution analyses). Isotope tracers are thus used at different stages of sample preparation to determine the extent of inter-species transformations and correct such analytical artefacts. Finally, a synthesis of the principal methods used for mercury speciation in seafood using isotope dilution analysis is presented.
Asunto(s)
Peces/metabolismo , Contaminación de Alimentos/análisis , Mercurio/análisis , Compuestos de Metilmercurio/análisis , Alimentos Marinos/análisis , Animales , Liofilización , Humanos , Espectrometría de Masas , Radioisótopos de Mercurio/química , Control de Calidad , Técnica de Dilución de Radioisótopos , Sensibilidad y EspecificidadRESUMEN
The excitation function of the proton exchange reactions on gold was investigated in the energy range from threshold up to 20MeV. We presented our experimental results upto 14MeV stacked-foil technique was used, the target was of high purity gold foils (99.99%.) Reactions cross-sections and excitation functions were studied. Both isomeric level cross sections of (197)Hg were measured and calculated theoretically using the DDHMS routine of the EMPIRE-II (v2.19) code. Isomeric cross-section ratios for the pair (197m,g)Hg were calculated and presented as a function of proton energy.
Asunto(s)
Oro/química , Oro/efectos de la radiación , Radioisótopos de Mercurio/química , Radioisótopos de Mercurio/efectos de la radiación , Modelos Químicos , Simulación por Computador , Radioisótopos de Mercurio/aislamiento & purificación , ProtonesRESUMEN
Seasonal trends of benthic methylmercury (methyl-Hg) production were examined in both littoral and open water sites of three lakes (Escondido, Moreno, and Morenito) in the North Andean Patagonia region of Argentina. Potentials of methyl-Hg production were measured by amending sediment samples with inorganic (197)Hg(II), incubating for either 24 and 32 h at room temperature, and subsequently assaying the radiolabelled organomercury produced. Seasonal variations of benthic methyl-Hg production were studied but no significant correlation was observed. Lake littoral sites exhibited up to two fold higher methyl-Hg production potentials in most cases. Sediment from lakes Moreno and Morenito generally exhibited much lower (up to 10 fold) methyl-Hg production potentials than those from Lake Escondido, possibly due to differences in particulate and dissolved organic matter quantity and quality, which is higher in Lake Escondido and primarily allochthonous, whereas in lakes Moreno and Morenito is primarily autochthonous. This study represents the first to directly examine benthic microbial Hg(II)-methylation in aquatic ecosystems of Patagonia.
Asunto(s)
Ecosistema , Mercurio/análisis , Compuestos de Metilmercurio/análisis , Contaminantes del Suelo/análisis , Argentina , Monitoreo del Ambiente , Sedimentos Geológicos/química , Radioisótopos de Mercurio/química , Compuestos de Metilmercurio/química , Estaciones del Año , Contaminantes del Suelo/químicaRESUMEN
The absolute 4pi-betagamma coincidence counting has been used to measure the activity concentrations of 54Mn and 203Hg, and the Sum-Peak method was used for 125I. 54Mn and 125I radionuclides have been part of international key-comparisons coordinated by the Bureau International des Poids et Measures (BIPM) in 2003/2004, while 203Hg is part of the traceability programme of the National Laboratory for Ionizing Radiation Metrology (LNMRI)/Brazil. Three different detectors were used for the Sum-Peak method: 3''x3'' NaI(Tl) and 5''x5'' well NaI(Tl) scintillation detectors and a planar germanium detector. Direct measurements were made of the photon emission probabilities of the 35.5-, 834.8- and 279.2-keV gamma-rays of 125I, 54Mn and 203Hg to give values of (0.0667+/-0.0014), (0.9997+/-0.0055) and (0.8161+/-0.0005), respectively. The half-lives of 203Hg and 54Mn were also determined by means of a 4pigamma ionization chamber (203Hg) and by the reference source method using a HPGe detector (54Mn) to give values of (46.639+/-0.023) days and (312.1+/-0.9) days, respectively.
Asunto(s)
Modelos Químicos , Radioisótopos/análisis , Radioisótopos/normas , Radiometría/métodos , Brasil , Simulación por Computador , Guías como Asunto , Semivida , Radioisótopos de Yodo/análisis , Radioisótopos de Yodo/química , Radioisótopos de Yodo/normas , Manganeso/análisis , Manganeso/química , Manganeso/normas , Radioisótopos de Mercurio/análisis , Radioisótopos de Mercurio/química , Radioisótopos de Mercurio/normas , Dosis de Radiación , Radioisótopos/química , Radiometría/normas , Estándares de Referencia , Valores de Referencia , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Batch studies have been carried out in the removal of Hg(II) from aqueous solutions by using well-synthesized and -characterized hydrous manganese oxide (HMO) and hydrous tin oxide (HTO) employing a radiotracer technique. Results obtained reveal that increased sorptive concentration (10(-8)-10(-2) mol dm(-3)), temperature (298-328 K), and pH (ca. 2.0-10.5) enhance the removal efficiency of these solids. First-order uptake of Hg(II) on HMO and HTO follows the Freundlich adsorption isotherm for entire concentration range. Positive values of DeltaH0 for the uptake process on both solids indicate endothermic uptake and desorption experiments point to irreversible uptake. Radiation stability of the adsorbents has also been assessed using a 300-mCi (Ra-Be) neutron source having an integral neutron flux of 3.85 x 10(6) N cm(-2) s(-1) and associated with a nominal gamma-dose of ca. 1.72 Gy/h.