Uranium speciation and distribution on the surface of Shewanella putrefaciens in the presence of inorganic phosphate and zero-valent iron under anaerobic conditions.

Shewanella putrefaciens (S. putrefaciens) is one of the main microorganisms in soil bioreactors, which mainly immobilizes uranium through reduction and mineralization processes. However, the effects of elements such as phosphorus and ZVI, which may be present in the actual environment, on the mineralization and reduction processes are still not clearly understood and the environment is mostly in the absence of oxygen. In this study, we ensure that all experiments are performed in an anaerobic glove box, and we elucidate through a combination of macroscopic experimental findings and microscopic characterization that the presence of inorganic phosphates enhances the mineralization of uranyl ions on the surface of S. putrefaciens, while zero-valent iron (ZVI) facilitates the immobilization of uranium by promoting the reduction of uranium by S. putrefaciens. Interestingly, when inorganic phosphates and ZVI co-exist, both the mineralization and reduction of uranium on the bacterial surface are simultaneously enhanced. However, these two substances exhibit a certain degree of antagonism in terms of uranium immobilization by S. putrefaciens. Furthermore, it is found that the influence of pH on the mineralization and reduction of uranyl ions is far more significant than that of inorganic phosphates and ZVI. This study contributes to a better understanding of the environmental fate of uranium in real-world settings and provides valuable theoretical support for the bioremediation and risk assessment of uranium contamination.

[Nano-silicon Dioxide Affects Apoptosis of Alveolar Macrophages via PI3K/AKt Signaling Pathway].

OBJECTIVE: To investigate the effect of phosphatidyl inositol 3-kinase/protein kinase B (PI3K/AKt) signaling pathway on the apoptosis of alveolar macrophages (AM) induced by nano-silica (NS) dust. METHODS: After exposure to different concentrations of NS suspension, CCK-8 assay was used to detect the AM viability; the cellular morphology of apoptotic AM was observed under fluorescence microscopy; the apoptosis rate and mitochondrial transmembrane potential of cells were detected by flow cytometry before and after pretreatment with phosphatidyl inositol 3-kinase (PI3K) inhibitor LY294002; Western blot was used to detect the expression of apoptosis-related proteins Bax, Bcl-2, p-PI3K and p-AKt. RESLUTS: The survival rate of AM was decreased in a time-dose relationship after NS exposure. With LY294002 pretreatment, the mitochondrial transmembrane potential level and the expressions of p-PI3K, p-AKt and Bcl-2 were decreased, the expression of Bax and the apoptosis rate were increased. CONCLUSION: Our data suggested that the activation of PI3K/AKt signaling pathway played an important role in NS-induced apoptosis in alveolar macrophages.

Photovoltage response of (XZn)Fe2O4-BiFeO3 (X=Mg, Mn or Ni) interfaces for highly selective Cr3+, Cd2+, Co2+ and Pb2+ ions detection.

High-photostability fluorescent (XZn)Fe2O4 (X=Mg, Mn or Ni) embedded in BiFeO3 spinel-perovskite nanocomposites were successfully fabricated via a novel bio-induced phase transfer method using shewanella oneidensis MR-1. These nanocomposites have the near-infrared fluorescence response (XZn or Fe)-O-O-(Bi) interfaces (785/832nm), and the (XZn)Fe2O4/BiFeO3 lattices with high/low potentials (572.15-808.77meV/206.43-548.1meV). Our results suggest that heavy metal ion (Cr3+, Cd2+, Co2+ and Pb2+) d↓ orbitals hybridize with the paired-spin X-Zn-Fe d↓-d↓-d↑↓ orbitals to decrease the average polarization angles (-29.78 to 44.71°), qualitatively enhancing the photovoltage response selective potentials (39.57-487.84meV). The fluorescent kinetic analysis shows that both first-order and second-order equilibrium adsorption isotherms are in line and meet the Langmuir and Freundlich modes. Highly selective fluorescence detection of Co2+, Cr3+ and Cd2+ can be achieved using Fe3O4-BiFeO3 (Langmuir mode), (MgZn)Fe2O4-BiFeO3 and (MnZn)Fe2O4-BiFeO3 (Freundlich mode), respectively. Where the corresponding max adsorption capacities (qmax) are 1.5-1.94, 35.65 and 43.7 multiple, respectively, being more competitive than that of other heavy metal ions. The present bio-synthesized method might be relevant for high-photostability fluorescent spinel-perovskite nanocomposites, for design of heavy metal ion sensors.

Enhanced Photovoltage Response of Hematite-X-Ferrite Interfaces (X = Cr, Mn, Co, or Ni).

High-fluorescent p-X-ferrites (XFe2O4; XFO; X = Fe, Cr, Mn, Co, or Ni) embedded in n-hematite (Fe2O3) surfaces were successfully fabricated via a facile bio-approach using Shewanella oneidensis MR-1. The results revealed that the X ions with high/low work functions modify the unpaired spin Fe2+-O2- orbitals in the XFe2O4 lattices to become localized paired spin orbitals at the bottom of conduction band, separating the photovoltage response signals (73.36~455.16/-72.63~-32.43 meV). These (Fe2O3)-O-O-(XFe2O4) interfacial coupling behaviors at two fluorescence emission peaks (785/795 nm) are explained via calculating electron-hole effective masses (Fe2O3-FeFe2O4 17.23 × 10-31 kg; Fe2O3-CoFe2O4 3.93 × 10-31 kg; Fe2O3-NiFe2O4 11.59 × 10-31 kg; Fe2O3-CrFe2O4 -4.2 × 10-31 kg; Fe2O3-MnFe2O4 -11.73 × 10-31 kg). Such a system could open up a new idea in the design of photovoltage response biosensors.

Mechanism of Fluorescence Enhancement of Biosynthesized XFe2O4-BiFeO3 (X = Cr, Mn, Co, or Ni) Membranes.

Ferrites-bismuth ferrite is an intriguing option for medical diagnostic imaging device due to its magnetoelectric and enhanced near-infrared fluorescent properties. However, the embedded XFO nanoparticles are randomly located on the BFO membranes, making implementation in devices difficult. To overcome this, we present a facile bio-approach to produce XFe2O4-BiFeO3 (XFO-BFO) (X = Cr, Mn, Co, or Ni) membranes using Shewanella oneidensis MR-1. The perovskite BFO enhances the fluorescence intensity (at 660 and 832 nm) and surface potential difference (-469 ~ 385 meV and -80 ~ 525 meV) of the embedded spinel XFO. This mechanism is attributed to the interfacial coupling of the X-Fe (e- or h+) and O-O (h+) interfaces. Such a system could open up new ideas in the design of environmentally friendly fluorescent membranes.

[Comparation of Toxic Effect of Silicious Mineral Dusts on Lung Epithelial A549 Cells].

Considering the high contents of minerals and the potential health risk of mineral dusts to human and the environment, this paper was aimed to figure out the toxic effect and mechanism of four common mineral particles (quartz, albite, sericite, and montmorillonite). Cytotoxicity assays for cell viability (MTT assay), membrane integrity (LDH assay), oxidative stress (H2O2 assay) and inflammatory cytokines (TNF-α and IL-6 assay) were applied. The results showed the influence of these mineral particles on A549 cell viability followed the order of momtmorillonite > cericite≥quartz > albite. There was no obvious relation between cell viability and the content of SiO2, however, good linear correlation with the content of iron, and the cytotoxicity of mineral dusts was strengthened with increasing iron content. Mineral dusts generated H2O2 in cell or cell-free systems. In particular, H2O2 exhibited a linear correlation with the iron content, which meant that iron in the mineral dusts played an important role in the generation of reactive radical. Among those samples, oxidative stress induced by montmorillonite was distinctly stronger, while there was negligible influence induced by quartz and albite. Besides, all the tested samples induced damage to A549 cell membrane, and triggered the release of TNF-α or IL-6, but differed by the kinds of mineral dusts. In conclusion, composition and structure directly affected, but were not the only factors that contributed to the biological activity of mineral dusts, the evaluation of cell viability, membrane damage, free radicals and inflammatory reaction induced by mineral dusts should take the external morphology, surface active groups, solubility, adsorption and ion exchange properties into consideration.

[Biosorption and Biomineralization of Uranium(VI) from Aqueous Solutions by Landoltia Punctata].

The biosorption and biomineralization characteristics of uranium by the duckweed Landoltia punctata was investigated in aqueous solutions enriched with 1 to 250 mg · L(-1) of U(VI) supplied as uranyl nitrate [UO2(NO3)2 · 6H2O]. The maximum uranium removal for the plant cultivar occurred at pH 4~5 of solution and their uranium removal efficiencies exceeded 90% after 24 h. In kinetics studies, the dried powder of duckweed can finished nearly 80% adsorption within 5 min, the batch adsorption equilibrium can be reached within 24 h for the living and dried powder of duckweed, Both for the living and dried powder of duckweed, the experimental data were well fitted by the pseudo-second-order rate model with the degree of fitting (r) higher than 0.99. The adsorption isotherms could be better described by the Freundlich model than the Langmuir model. In addition, Fourier transform infrared spectroscopy (FTIR) revealed that the surface of Landoltia punctata possess many active groups such as hydroxyl, carboxyl, phosphate and amide groups, the hydroxyl, amino groups involved in adsorption of U(VI) by living and dried powder of Landoltia punctata, and the phosphate groups also participated in the adsorption behavior of U(VI) by the living Landoltia punctata. The living Landoltia punctata reduction part of U(VI) to U(IV) was observed by XPS analysis. SEM and energy dispersive X-ray spectroscopy (EDS) of duckweed from 10~200 mg · L(-1) uranium treatments indeed showed root surface of living Landoltia punctata formed a significant portion of U precipitates with nanometer sized schistose structures that consisted primarily U and P, not containing C. Inorganic phosphate was released by the root cells of Landoltia punctata during the experiments providing ligands for formation of insoluble U(VI) and U(IV) phosphates. The distinct uranium peaks in the EDS spectra of the cluster on the root surface can be observed after biosorption and the uranium and phosphorus mass ratio of the cluster spot was measured to be 82.5% and 8.76% of the total component weight, respectively, and the atomic percentage of 30.89% and 25.19%, respectively. It is worth noting that the phosphorus mass ratio and the atomic rate of the control group is only 0.24% and 0.11%, respectively. But there was no similar crystals observed on the surface of dried powder of Landoltia punctata after biosorption. The present work suggests that living and dried powder of Landoltia punctata can remove more than 90% U(VI) from solution simultaneously precipitated together with phosphate by the living Landoltia punctata, and the dried powder of Landoltia punctata adsorption U(VI) is mainly through the effect of electrostatic attraction, ion exchange and complexation coordination, etc. Here, for the first time, the presence of U immobilization mechanisms within one aquatic plant is reported using Landoltia punctata.

[Biosorption of Radionuclide Uranium by Deinococcus radiodurans].

As a biological adsorbent, Living Deinococcus radiodurans was used for removing radionuclide uranium in the aqueous solution. The effect factors on biosorption of radionuclide uranium were researched in the present paper, including solution pH values and initial uranium concentration. Meanwhile, the biosorption mechanism was researched by the method of FTIR and SEM/EDS. The results show that the optimum conditions for biosorption are as follows: pH = 5, co = 100 mg · L(-1) and the maximum biosorption capacity is up to 240 mgU · g(-1). According to the SEM results and EDXS analysis, it is indicated that the cell surface is attached by lots of sheet uranium crystals, and the main biosorpiton way of uranium is the ion exchange or surface complexation. Comparing FTIR spectra and FTIR fitting spectra before and after biosorption, we can find that the whole spectra has a certain change, particularly active groups (such as amide groups of the protein, hydroxy, carboxyl and phosphate group) are involved in the biosorption process. Then, there is a new peak at 906 cm(-1) and it is a stretching vibration peak of UO2(2+). Obviously, it is possible that as an anti radiation microorganism, Deinococcus radiodurans could be used for removing radionuclide uranium in radiation environment.

Computational Study of the Cation-Modified GSH Peptide Interactions With Perovskite-Type BFO-(111) Membranes Under Aqueous Conditions.

We elucidated a number of facets regarding glutathione (GSH)-bismuth ferrite (BiFeO3, BFO) interactions and reactivity that have previously remained unexplored on a molecular level. In this approach, the cation-modified reduced GSH (or oxidised glutathione (GS·)) formed on the (111)-oriented BiFeO3 membrane (namely BFO-(111)) can serve as an efficient quencher, and the luminescence mechanism is explained in aqueous conditions. Notably, we suggest the use of Fe(2+)↓ ion as an electron donor and K(+) ion as an electron acceptor to exert a "gluing" effect on the glutamic acid (Glu) and glycine (Gly) side chains, producing an exposed sulfhydryl (-SH) configuration. This method may enable the rational design of a convenient platform for biosensors.

DFT and two-dimensional correlation analysis methods for evaluating the Pu(3+)-Pu(4+) electronic transition of plutonium-doped zircon.

Understanding how plutonium (Pu) doping affects the crystalline zircon structure is very important for risk management. However, so far, there have been only a very limited number of reports of the quantitative simulation of the effects of the Pu charge and concentration on the phase transition. In this study, we used density functional theory (DFT), virtual crystal approximation (VCA), and two-dimensional correlation analysis (2D-CA) techniques to calculate the origins of the structural and electronic transitions of Zr1-cPucSiO4 over a wide range of Pu doping concentrations (c=0-10mol%). The calculations indicated that the low-angular-momentum Pu-fxy-shell electron excites an inner-shell O-2s(2) orbital to create an oxygen defect (VO-s) below c=2.8mol%. This oxygen defect then captures a low-angular-momentum Zr-5p(6)5s(2) electron to form an sp hybrid orbital, which exhibits a stable phase structure. When c>2.8mol%, each accumulated VO-p defect captures a high-angular-momentum Zr-4dz electron and two Si-pz electrons to create delocalized Si(4+)→Si(2+) charge disproportionation. Therefore, we suggest that the optimal amount of Pu cannot exceed 7.5mol% because of the formation of a mixture of ZrO8 polyhedral and SiO4 tetrahedral phases with the orientation (10-1). This study offers new perspective on the development of highly stable zircon-based solid solution materials.

First principles simulation of temperature dependent electronic transition of FM-AFM phase BFO.

Understanding how temperature affects the electronic transitions of BFO is important for design of BiFeO3 (BFO)-based temperature-sensitive device. Hitherto, however, there have been only very limited reports of the quantitative simulation. Here, we used density functional theory (DFT) and two-dimensional correlation analysis (2D-CA) techniques to calculate the systematic variations in electronic transitions of BFO crystal, over a range of temperature (50~1500 K). The results suggest that the heat accumulation accelerates the O-2p(4) orbital splitting, inducing the Fe(3+)-3d(5) → Fe(2+)-3d(5)d(0) charge disproportionation. The origin is observed as the temperature-dependent electron transfer process changes from threefold degeneracy to twofold degeneracy. Additionally, the crystallographic orientation (111) can be used to control the 2p-hole-induced electronic transition as O → unoccupied Fe(3+)-3d(5), in comparison to the O → Bi-6p(3) + Fe(3+)-3d(5)d(0) on the orientations (001) and (101). This study offers new perspective on the improvement of BFO-based temperature-sensitive device.

[Quantitative detection of hydroxyl radical generated in quartz powder/phosphate buffer solution system by fluorescence spectrophotometry].

Quartz powder would release radical hydroxyl in phosphate buffer solution. In order to detect the quantity of radical hydroxyl with a quite low concentration, the present paper established a fluorescence method. According to the relationship between the concentration of 2-hydroxyl of terephthalic acid (HOTP) and fluorescence intensity at the wavelength of EX(max)/EM(max) = 316 nm/422 nm, a working standard curve was constructed. Then through the filtrated fluorescence intensity obtained from the powder and solution system, cumulative concentration of * OH can be measured indirectly. By repeating tests and analysis of five different experimental conditions of * OH cumulative concentration, the minimum detection limit of the method reached 1.59 x 10(-10) mol x L(-1), with a relative deviation of 1.20%-7.89%, standard deviation was 1.09 x 10(-9)-2.17 x 10(-9) mol x L(-1) and the relative standard deviation was 3.5%-5.8%. The method features high accuracy and good repeatability performance. Compared to other quantitative studies, this method might be applied to test radical hydroxy produced in pH neutral solution systems. In addition, it has apparent advantages such as low detection limit, low cost, higher sensitivity, and better stability and reproducibility. That provides the means for the quantitative study of mixed systems consisting of quartz powder and phosphate buffered solution.

[Characteristics of U (VI) biosorption by biological adsorbent of platanus leaves].

The platanus leaves were used as adsorbent to study uranium removal efficiency from aqueous solution on the basis of adsorption kinetics and isotherm equations. Static adsorption affected by initial pH values and contact time was analyzed, and surface characteristics of platanus leaves and uranium removal mechanism were investigated with the help of SEM, FTIR, XRD and XRF. The adsorption process fits pseudo-second-order kinetic model and Freundlich isotherm equation, and the maximum adsorption capacity for uranium was 19.68 mg x g(-1). Results showed that hydroxyl groups, amides II belt and carboxyl active functional groups were important for uranium removal. Structure characteristic adsorption band of cellulose was found in XRD spectra, uranium was detected, and also Ca and Na elements of the content increased. Mg element content relative decrease was found on platanus leaves after adsorption by XRF, and it proved the reaction feasibility. Speculation for the behavior of uraniu adsorption by platanus leaves was both physical adsorption and chemical adsorption, exhibiting joint action of electrostatic attraction, redox reaction, chelating ligand and ion exchange.

[FTIR analysis of Sr2+ biosorption by Bacillus spp. strains isolated from soil treated with gamma-ray radiation].

One strain bacterium was isolated from purple soil of Sichuan basin. It was subject to Bacillus according to analysis results of 16S rDNA. The effect of its biosorption to Sr2+ under gamma-ray radiation was studied in this paper. As for the whole kinetic biosorption curves, the results show that bacterial growth rates of test groups have retardation phenomena compared to the control groups without radiation. Such as the appearance of biosorption equilibrium retarded 1.5 d while the max growth rate retarded 0.5 d after the radiation SEM analysis showed that the bacterial cells had abnormity distortion after radiation. This proved that gamma-ray radiation can bring obvious damage to experimental bacterial cells. FTIR analysis results indicated that bacteria cells were damaged by radiation and Sr2+ has cooperation damage effects with radiation in aqueous condition, and the bacterial cells of log phase are easier to be damaged by coming forth radiation than those of lag phase. This radiation damage under different radiation condition mainly leads to that the characteristic peaks of amylase, protein amide and lipids on bacterial cells are slightly shifted.

[Comparative study of the cytotoxicity induced by chrysotile asbestos, rock wool and substitute fibers in vitro].

OBJECTIVE: To study the cytotoxicity induced by chrysotile asbestos (CA), rock wool (RW) and wollastonite (WS). METHODS: V79 cells were divided into 4 groups. i.e. CA group, WS group, RW group and control group (200 microl PBS). The exposure concentration of dusts was 100 mg/L, The cell viability was detected by MTT and lactate dehydrogenase (LDH) activity assays. The technique of scanning electron microscopy was used to examine the change of V79 cells. RESULTS: SiO2 was main constituent for 3 kinds of dusts. In MTT assay, the cell viability of RW and WS groups was 64.8% and 65.7%, respectively, which were significantly higher than that (54.5%) of CA group (P < 0.01). In LDH assay, the LDH activity of RW and WS groups [(15.7 +/- 50.9), (12.3 +/- 3.7) U/L, respectively] was significantly lower than that [(20.2 +/- 0.9) U/L] of CA group (P < 0.05). In scanning electron microscopy examination, it was found that the two ends of V79 cells in CA group contained a great deal of fibers remaining bodies, but the V79 cell appearance in RW and WS groups was normal. CONCLUSION: The cytotoxicity induced by RW and WS is significantly lower than that induced by CA for V79 cell.

Research on the additives to reduce radioactive pollutants in the building materials containing fly ash.

Several kinds of functional additives such as barite, zeolite, ferric oxide, gypsum, and high alumina cement were introduced to prepare a low-radiation cement-based composite to reduce radioactive pollutants contained in fly ash. The effect of content and granularity of the functional additives on the release of radioactive pollutants were investigated. Composites were characterized by X-ray diffraction, Scan electron microscopy. The results indicate that the radioactive pollutants contained in the fly ash can be reduced by adding a proper amount of zeolite, ferric oxide, gypsum, and high alumina cement. The release of radon from fly ash decreases with a decrease in the granularity of additives. Compared with traditional cement-based composite containing fly ash, the release of radon can be reduced 64.8% in these composites, and the release of gamma-ray is decreased 45%. Based on the microstructure and phase analysis, we think that by added functional additives, there are favorable to form self-absorption of radioactivity in the interior composites. This cement-based composite will conducive to fly ash are large-scale applied in the field of building materials.

[Biosorption of lead ions on dried waste beer yeast and the analysis by FTIR].

The biosorption of lead ions on dried waste beer yeast was investigated with respect to the adsorption conditions and the biosorption mechanism was analyzed with the instruments of AAS, SEM/EDS and FTIR. The results show that the metal uptake value obtained was 47.6 mg x g(-1) and the adsorptive efficiency was above 90%. Under our experiment conditions, the biosorption of Pb2+ on dried waste beer yeast is a fast process. The biosroption quantity of Pb2+ on beer yeast cells was 47.6 mg x g(-1) and the adsorption efficiency obtained was 91.6% in fisrt 30 min, then the metal uptake value obtained was 48.8 mg x g(-1) and the adsorptive efficiency was above 94% at 90 min. The cells cracking and breaking off were seen after the biosorption of lead ions on beer yeast through SEM analysis, and the cytoplasts from yeast cell should be responsible for the last period biosorption of lead ions. EDS analysis also proved that lead ions were absorbed on the yeast cells. FTIR analysis showed that the infrared spectrograms are different at different pH and biosorption time, especially hydroxyl groups, carboxylate groups and amide groups have obviously changed. Amylase and amide of protein were considered as main components to participate the chemical absorption of lead ions on yeast cells. Consequently, dried waste beer yeast is an inexpensive, readily available adsorbent for metals and especially has a high adsorption capacity for lead ions.

[Spectra study on the varied features of crocidolite fibers in rat].

OBJECTIVE: To further study the pathogenic mechanism of crocidolite, the imperceptible changes of crocidolite surface in rat were observed. METHODS: The animal model was established and the changes in the rat infected with dust were observed by use of microscopy, SEM, differential thermal analysis and IR spectroscopy. RESULTS: In the course of interaction between organism protein and crocidolite, the protein symmetry decreased and structure loosened. The silicon of crocidolite was bonded with the alkyl, amido- of protein. New absorption bands of Si-O-C(N), Si-R clearly appeared. The organism cleared the dust by means of dissolution, enwrapping, winding or in the way of biochemical dissolution, and the fibre became shortened, broken, bifurcated, ends-rounded, and also it could dissolve, transfer and chemically react on surface. CONCLUSION: The results showed that the surface radicals of asbestos fibre reacted with some albumen in tissue and hence formed new surface mediator. It is a new form of dissolution and reaction of fibre in vivo that fibres in alveoli transform to carbonate. The residual substances of crocidolite are mainly Si-O. Tissue membrane is the retardation cingulum of dust transference in vivo.