Latest ArticlesPlutonium (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.
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.
Actinide metallacycles are an emerging class of functional coordination assemblies, but multi-level assembly from metallacycle units toward hierarchical supramolecular structures are still rarely investigated. In this work, we put forward a novel supramolecular inclusion-based method through introducing two macrocyclic hosts, cucurbit[7]uril (CB[7]) and cucurbit[8]uril (CB[8]) to facilitate hierarchical assembly of uranyl metallacycles with higher complexity, and successfully prepare two different kinds of uranyl metallacycle-based complexes with intriguing hierarchical structures, a CB[7]-based four-member molecular necklace ([4]MN) and a CB[8]-involved ring-in-ring supramolecular polymer chain. The results obtained here prove the feasibility of supramolecular inclusion for regulating coordination assembly of uranyl metallacycles and related hierarchical structures. It is believed that this method can be used to achieve the construction of actinide coordination assemblies with higher structural complexity.
Thioredoxin reductase 1 (TrxR1) is over activity in tumor cell to maintain their redox balance. Although gold clusters have great potential in antitumor drug as they could well inhibit TrxR1, the molecular mechanism has not been disclosed yet. In this work, we revealed gold clusters can well inhibit the activity of TrxR1 in lung tumor cells and further disclosed the inhibition mechanism by using computational simulation methods. We firstly inferred the binding sites of gold in the hydrophobic cavities on TrxR1. The simulation results show that the gold ion (released from Au cluster) interact with –SH of Cys189 in TrxR1, this greatly increase the distance between the C-terminal redox center of TrxR1 and the Trx redox center, thereby destroy the electron transfer pathway between them. Our electron transfer destroying mechanism is different from the previous hypothesis that gold binds to the Sec498 of TrxR1 which has never been proved by experimental and theory studies. This work provides a new understanding of the gold clusters to inhibit TrxR1 activity.
The hunt for agents that are suitable for actinide decorporation to reduce the whole-body load of actinide in accidental internal exposure is the ever-lasting goal in radiation protection and medical treatment in nuclear emergency. All current decorporation agents can be categorized as two groups, one is the molecular ligands, and the other is the nanoparticles decorated with molecular ligands. Here in this work, functional nanodiamonds (fNDs) with ssDNA (the endogenous biomacromolecule rich in phosphate groups) loaded on the NDs is reported, which poses good uranyl adsorption selectivity, high cellular uptake, fast excretion, and effective decorporation of uranyl from rat renal proximal tubular epithelial cells (NRK-52E). All those results corroborate that fNDs can potentially serve as a brand new family of chelators for actinide decorporation.
Phototheranostics have attracted tremendous attention in cancer diagnosis and treatment because of the noninvasiveness and promising effectiveness. Developing advanced phototheranostic agents with long emission wavelength, excellent biocompatibility, great tumor-targeting capability, and efficient therapeutic effect is highly desirable. However, the mutual constraint between imaging and therapeutic functions usually hinders their wide applications in biomedical field. To balance this contradiction, we herein rationally designed and synthesized three novel tumor-targeted NIR-II probes (QR-2PEG321, QR-2PEG1000, and QR-2PEG5000) by conjugating three different chain lengths of PEG onto an integrin αvβ3-targeted NIR-II heptamethine cyanine fluorophore, respectively. In virtue of the essential amphiphilic characteristics of PEG polymers, these probes display various degree of aggregation in aqueous buffer accompanying with differential NIR-II imaging and photothermal (PTT) therapeutic performance. Both in vitro and in vivo results have demonstrated that probe QR-2PEG5000 has the best NIR-II imaging performance with prominent renal clearance, whereas QR-2PEG321 possesses excellent photoacoustic signal as well as PTT effect, which undoubtedly provides a promising toolbox for tumor diagnosis and therapy. We thus envision that these synthesized probes have great potential to be explored as a toolkit for precise diagnosis and treatment of malignant tumors.
The complexation of pentavalent neptunium, Np(V), with nitrate ion in an ionic liquid solution has been studied spectroscopically for the first time. The characteristic f-f transition absorption band of Np(V) in the NIR region changes significantly upon the titration of nitrate ion into the solution, revealing strong complexation of Np(V) with nitrate ion in the ionic liquid. Most notably, the absorption band of Np(V) almost disappears when a sufficiently high concentration of nitrate ion is present in the solution. Such a rare optically "silent" species can be assigned to the 1:2 Np(V)/nitrate complex with a centrosymmetric coordination environment where Np sits at the inversion center.
The development of uranyl ion detection technology has exhibited its significance in public security and environmental fields for the radioactivity and chemical toxicity of uranyl ion. The WHO standard of uranyl ion makes it necessary to develop highly sensitive uranyl rapid warning system in drinking water monitoring. Herein, a visualized rapid warning system for trace uranyl ion is carried out based on electrochemiluminescence (ECL) imaging technology to give an ultra-low limit of detection (LOD) and high selectivity. Amidoxime, a bi-functional group with both uranyl ion capturing and co-reactive functions, is modified on a conjugated polymer backbone with strong ECL signal to be prepared into three-in-one polymer nanoparticles (PNPs) with self-enhanced ECL property. The captured uranyl ion can enhance the ECL signal of PNPs via resonance energy transfer process to give the LOD as 0.5 ng/L, which is much lower than the known luminescent uranyl sensors. Furthermore, ECL imaging technology is introduced into realizing visualized uranyl rapid warning, and can be successfully applied on natural water samples. This study provides a novel strategy for uranyl rapid warning, and shows its potential meaning in public security and environmental fields.
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.
The in vivo degradation behavior of metallic nanoparticles (NPs) is very important for their biomedical applications and safety evaluation. Here, a method of laser ablation-single particle inductively coupled plasma mass spectrometry (LA-sp-ICP-MS) is shown to have high spatial resolution, sensitivity and accuracy for simultaneous imaging the in situ distribution of particulate Ag (P-Ag) and released ionic Ag (Ion-Ag) in the sub-organs of spleen, liver and kidney after intravenous injection of Ag nanoparticles (50 nm, AgNPs) to mice. Under the optimized parameters of 0.4 J/cm2 laser fluence on a 30 µm spot with dwell time at 100 µs, the signals of P-Ag and Ion-Ag in the organic tissues can be easily distinguished from the mass spectra. The method of iterative threshold algorithm has been used to distract the signals of P-Ag and Ion-Ag and separate each other. The resulting images for the first time provide visualized evidence that a considerable amount of P-Ag accumulated in the splenic marginal zone, but widely distributed in the liver parenchyma at 24 h after injection of AgNPs, and in the meantime, obvious amounts of ionic Ag released and distributed in the organs. In addition, the imaging results indicate that the AgNP excretion in the kidney is mainly in ionic forms. The investigation here demonstrates that the developed LA-sp-ICP-MS method with high spatial resolution, sensitivity and visualization capability can become a powerful tool in the clinical context of metallic NPs.
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