Latest ArticlesInternal contamination of actinides has led to significant health hazards to the public and workers in the context of nuclear power plant accidents, uranium ore mining, and reprocessing of the used fuel. An effective sequestering agent that is able to remove accidentally incorporated actinides in vivo with low toxicity is always in urgent need. The molecular decorporation ligands have been the most widely researched agents for the past few decades, while preliminary studies of functionalized nanoparticles have shown their clear advantages in metal binding selectivity, toxicity, and oxidative stress alleviation. Herein, the state-of-the-art of those two types of decorporation agents is presented with special attention being paid on the correlation between the solution and solid-state chemistry of those agents with actinides and the corresponding decorporation efficacies.
Uranium removal from aqueous solutions using environmentally friendly photocatalytic technology is a novel approach for resource recovery. Herein, carbon nitride/activated carbon composite materials (CN/AC) were investigated for U(Ⅵ) reduction under visible light. An exceptional boost in photocatalytic activity was observed for CN/AC composites (up to 70 times over the conventional bulk g-C3N4). The strong interactive conjugated π-bond structure between g-C3N4 and AC accelerated the migration of carriers and then prolonged the electron lifetime. CN/AC composites exhibited excellent compatibility with different water substrates and were resilience to a wide range of pH changes and abundant competitive anions/cations. Quenching experiments and electron microscopy characterization indicated that U(Ⅵ) was reduced by photogenerated electrons and deposited on the edge of CN/AC composites. The low-cost, high-performance carbon-based composite material proposed in this work is a potential candidate for the efficient treatment of radioactive wastewater.
Soft N-donor bis-triazin bipyridines derives (R-BTBP) are a type of very promising extratant for extraction and complexation with long-lived trivalent minor actinides over lanthanides from highly active liquid waste (HLW). In addition to minor actinides, R-BTBP also holds very strong complexation ability toward fission palladium. However, few studies have been focused on the separation and complexation with the fission product Pd(Ⅱ) by R-BTBP. Herein, the complexation behaviors of Pd(Ⅱ) with four typical R-BTBP ligands were systematically studied by single crystal X-ray diffraction, 1H NMR titration and theoretical calculation. The effects of R-BTBP initial conformation and nitrate anions on the complexation behaviors of R-BTBP with Pd(Ⅱ) were thoughtfully analyzed. Both the 1:1 and 2:1 binuclear complexes could be formed between Pd(Ⅱ) and R-BTBP with initial Ⅱ conformation in the presence of nitrate anions, while only one 1:1 type Pd(Ⅱ) complex could be formed for those with initial OO conformation. Without nitrate anion, only one 1:1 type complex was formed in solution. The structure of the 1:1 Pd(Ⅱ)/R-BTBP complex was firstly characterized by single crystal crystallography. DFT calculation results showed that a significant large rotational energy barrier (21.8~22.6 kcal/mol) must be overcome to form the Ⅱ type 2:1 Pd(Ⅱ) complex for those OO type R-BTBP ligands, however which would not prevent them from forming the 1:1 type complex.
Radionuclide imaging is now the premier imaging method in clinical practice for its high sensitivity and tomographic capability. Current clinically available radio imaging methods mostly use positron-emission tomography (PET) and single-photon emission computed tomography (SPECT) to detect anatomic abnormalities that conventional imaging techniques typically have challenges for visualizing. Contrast agents are indispensable for radionuclide imaging, and the radionuclide is always attached to a suitable vector that achieves targeted delivery. Nowadays, peptides have attracted increasing interest in targeting vectors of contrast agents, mainly due to their high specificity for target receptors at nanomolar concentrations and low toxicity. Radiolabeled peptide probes as kinds of PET/SPECT tracers had become essential tools for clinical radionuclide diagnosis. This review mainly summarizes radiolabeled peptide probes for bioimaging, including fundamental concepts of radiolabeled peptide probe design, some typical peptide analogs radiocontrast agents for PET, SPECT, and the combination imaging.
Astatine-211 (211At, t1/2 = 7.21 h) emitting two α particles with energies of 5.87 and 7.45 MeV, can lead to a high linear energy transfer (LET = 98.84 keV/µm) and short tissue range (50~90 µm). Since the 1950s, 211At had stepped into endoradiotherapy and has always been regarded as one of the most promising α-emitters for targeted-alpha therapy (TAT) in various malignancies. In the past two decades, 211At related radiopharmaceuticals have achieved great progress in the studies of basic physicochemical properties of astatine, 211At labeling strategies, preclinical and clinical studies, producing profound effects in nuclear medicine. This work will give a panorama of 211At-related researches in the recent 20 years, which will cover both the fundamental insights of 211At radiochemistry and applied labeling compounds. It can provide some important hints for the studies of TAT and other radiopharmaceuticals applied in tumor radiotherapy.
Based on the outstanding application advantages of nitrogen-rich materials with regular porous frameworks in the capture of gaseous radioactive iodine, a series of covalent organic frameworks (COFs) with dual channels and abundant tertiary-amine active sites were constructed herein via a unique multi-nitrogen node design. The high density of up-to-six nitrogen adsorption sites in a single structural unit of the products effectively improved the adsorption capacities of the materials for iodine. Moreover, the adsorption affinity of the active sites can be further regulated by charge-induced effect of different electron-donating groups introduced into the COFs. Adsorption experiments combined with DFT theoretical calculations confirmed that the introduction of electron-donating groups can effectively increase the electron density around the active sites and enhance the binding energy between the materials and iodine, and thus improve the iodine adsorption capacity to 5.54 g/g. The construction strategy of multi-nitrogen node and charge-induced effect proposed in this study provides an important guidance for the study of the structure-activity relationship of functional materials and the design and preparation of high-performance iodine adsorption materials.
The abundances of heavy elements produced in r-process nucleosynthesis in the early solar system need experimental verification. 244Pu could be the heaviest primordial nuclide produced before the formation of the Earth still being detectable today. As recent attempts failed to confirm the discovery of 244Pu signals at a concentration of 1.0 × 10−18 g/g in bastnaesite reported by Hoffman et al. in this study, the total primordial 244Pu in 450 g bastnaesite sample from Bayan Obo ore (China) was measured using ultra-sensitive compact accelerator mass spectrometry (AMS). As no 244Pu signal was detected, an upper limit for the 244Pu in our bastnaesite sample was estimated to be 2.1 × 10−20 g/g at 99% confidence level.
Tumor-related PD-L2 expression is associated with the clinical efficacy of PD-1/PD-L1 blockade therapy. PD-L2-specific imaging can help selecting patients for appropriate immunotherapy. In this study, a PD-L2-targeting peptide (PDP2) was screened by the one-bead one-compound combinatorial library approach. Using the retro-inverso D-peptide of PDP2 (RD-PDP2) and PEGylation strategies, we developed a novel Tc-99m-labeled PD-L2-targeting peptide as a SPECT tracer (99mTc-PEG6-RD-PDP2) for imaging of tumor PD-L2 expression. The radiolabeling yield of 99mTc-PEG6-RD-PDP2 was greater than 95% by the standard HYNIC/tricine/TPPTS labeling procedure. 99mTc-PEG6-RD-PDP2 displayed high PD-L2-binding specificity both in vitro and in vivo. SPECT/CT imaging with 99mTc-PEG6-RD-PDP2 showed that the A549-PD-L2 tumors were clearly visualized, whereas the signals in PD-L2-negative A549 tumors were much lower. In vivo blocking study suggested that the tumor uptake of 99mTc-PEG6-RD-PDP2 was PD-L2 specifically mediated. 99mTc-PEG6-RD-PDP2 is a promising SPECT probe for the non-invasive imaging of tumor PD-L2 expression and has a great potential in guiding the anti-PD-1 or anti-PD-L1 immunotherapy of cancer.
A simple and convenient method has been developed for the pre-concentration and separation of inorganic selenium species from environmental water samples using anion exchange chromatographic column combined with high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) measurement. 75Se(Ⅳ) and 75Se(Ⅵ) were prepared and used as tracers during the experiments. The volatility of selenium during solution evaporation was investigated to establish a reliable water samples pretreatment procedure. The parameters which affect the uptake of Se(Ⅳ) and Se(Ⅵ) on Dowex1 × 8 resin was optimized and the procedure for Se(Ⅳ) and Se(Ⅵ) separation was proposed. Both Se(Ⅳ) and Se(Ⅵ) are retained on the column in natural or alkaline solution with high distribution coefficient. The successive gradient elution of pre-concentrated species of selenium with HNO3 solution allows to differentiate between them. Se(Ⅳ) and Se(Ⅵ) finally were eluted with 0.05 mol/L HNO3 and 5.0 mol/L HNO3, respectively. The proposed method has been successfully verified using the certified reference materials (CRMs) of real water samples, and spiked recoveries for real samples were 98%-104% with 5% relative standard deviations (RSDs). The developed procedure is proved to be reliable and can be used for the rapid determination of selenium species in environmental water samples.
Plutonium (Pu) is an anthropogenic radionuclide which mainly derived from atmospheric nuclear tests in the environment. In this study, the Pu isotopes (239Pu and 240Pu) in aerosol samples collected during the sandstorm and non-sandstorm period were measured by accelerator mass spectrometry (AMS) and the behavior of Pu was studied. The activity concentrations of 239Pu and 240Pu in the aerosol samples of Beijing were ranged from 0.62 nBq/m3 to 99.6 nBq/m3 for 239Pu and 3.51 nBq/m3 to 60.23 nBq/m3 for 240Pu, respectively. 239Pu and 240Pu concentrations exhibited a remarkable seasonal variation trend, with the higher results showed in spring, and the relatively lower concentrations in winter. The observed higher concentration of 239Pu and 240Pu detected in sandstorm samples further indicated Pu was closely related to the occurrence of sandstorms. The global fallout characteristics of 240Pu/239Pu atom ratios (average 0.20, ranging from 0.16 to 0.27) in aerosol samples indicating that global fallout was the major source of Pu in the atmosphere. Using aluminum (Al) as an indicator of soil resuspension, significant positive correlation between 239Pu and Al (r2 = 0.934), 240Pu and Al (r2 = 0.525) revealed that soil resuspension was a primary source of atmospheric Pu in Beijing. These results implied that the combination of 239Pu, 240Pu and Al could be used as the potential tracer of sandstorm.
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