Biosorption of uranium on Bacillus sp. dwc-2: preliminary investigation on mechanism

In this paper, the biosorption mechanisms of uranium on an aerobic Bacillus sp. dwc-2, isolated from a potential disposal site for (ultra-) low uraniferous radioactive waste in Southwest China, was explored by transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, FT-IR spectroscopy, proton induced X-ray emission (PIXE) and enhanced proton backscattering spectrometry (EPBS). The biosorption experiments for uranium were carried out at a low pH (pH 3.0), where the uranium solution speciation is dominated by highly mobile uranyl ions. The bioaccumulation was found to be the potential mechanism involved in uranium biosorption by Bacillus sp. dwc-2, and the bioaccumulated uranium was deposited in the cell interior as needle shaped particles at pH 3.0, as revealed by TEM analysis as well as EDX spectra. FTIR analysis further suggested that the absorbed uranium was bound to amino, phosphate and carboxyl groups of bacterial cells. Additionally, PIXE and EPBS results confirmed that ion-exchange also contributed to the adsorption process of uranium. All the results implied that the biosorption mechanism of uranium on Bacillus sp. is complicated and at least involves bioaccumulation, ion exchange and complexation process.

Synthesis of Water-Soluble Cyclen-Functionalised Fullerene C60 Derivatives

The fullerene family has interesting photophysical, electrochemical and mechanical properties with applications in organic solar cells, nanotechnology, superconductivity, chemosensors and biomedicine. Water-soluble cyclen-functionalised fullerene derivatives cyclen-C60-1 and bis(cyclen)-C60-2 have been synthesised. The whole synthetic routes are simple and the total yields are relatively high.

Strontium adsorption on tantalum-doped hexagonal tungsten oxide

Hexagonal tungsten oxide (hex-WO3) has the potential to separate (137)Cs and (90)Sr from nuclear power plant or fission (99)Mo production waste. This study aims to increase the capacity of hex-WO3 to adsorb Sr(2+). Ta-doped hex-WO3 was synthesized by the hydrothermal treatment of sodium tungstate dihydrate and tantalum chloride in concentrated HCl, in the presence of ammonium sulfate. Incorporating Ta into the WO3 framework caused the interlayer spacing to expand, and the band gap to shift to higher energy. The Sr(2+) adsorption capacity of Ta-doped hex-WO3 was significantly higher than that of hex-WO3. Sr(2+) adsorption reached equilibrium within 2h in acidic solution. Maximum Sr(2+) removal occurred at pH 4. Sr(2+) uptake by hex-WO3 was described better by the Freundlich model than by the Langmuir model. Sr(2+) adsorption on hex-WO3 was spontaneous under the studied conditions.

CMPO-calix[4]arenes with spacer containing intramolecular hydrogen bonding: effect of local rigidification on solvent extraction toward f-block elements

To understand intramolecular hydrogen bonding in effecting liquid-liquid extraction behavior of CMPO-calixarenes, three CMPO-modified calix[4]arenes (CMPO-CA) 5a-5c with hydrogen-bonded spacer were designed and synthesized. The impact of spacer rotation that is hindered by introduction of intramolecular hydrogen bonding upon extraction of La(3+), Eu(3+), Yb(3+), Th(4+), and UO2(2+) has been examined. The results show that 5b and 5c containing only one hydrogen bond with a less hindered rotation spacer extract La(3+) more efficiently than 5a containing two hydrogen bonds with a more hindered rotation spacer, demonstrating the importance of local rigidification of spacer in the design of extractants in influencing the coordination environment. The large difference in extractability between La(3+) and Yb(3+) (or Eu(3+)) by 5b (or 5c), and the small difference by 5a, suggests intramolecular hydrogen bonding do exert pronounced influence upon selective extraction of light and heavy lanthanides. Log-log plot analysis indicates a 1:1, 2:1 and 1:1 stoichiometry (ligand/metal) for the extracted complex formed between 5b and La(3+), Th(4+), UO2(2+), respectively. Additionally, their corresponding acyclic analogs 7a-7c exhibit negligible extraction toward these metal ions. These results reveal the possibility of selective extraction via tuning local chelating surroundings of CMPO-CA by aid of intramolecular hydrogen bonding.

Regioselective Synthesis of 2- and 3-Substituted Imidazo[1,2-a]pyridines

A range of 2- or 3-substituted imidazo[1,2- a]pyridines were prepared from 2-aminopyridine derivatives and gem-dibromovinyl compounds by the tandem nucleophilic substitution (or nucleophilic addition)/cyclisation reaction.

[A new radiopharmaceutical for bone imaging: experimental study of 99mTc-HEDTMP]

The purpose of this study is to prepare 99mTc-HEDTMP [N-(2-hydroxyethyl) ethlenediamine-1,1,2-tri (methylene phosphonic acid), a new kind of bone seeking compound; to investigate its biological properties; and to explore the possibility of using it as a potential radiopharmaceutical for skeleton scintigraphy. HEDTMP was labeled with 99mTc by "pretinning" method, the radiochemical purity was 97.00% +/- 0.34%. 99mTc-HEDTMP was found to be stable in 5 hours in vitro with the radiochemical purity over 95% even after being diluted by physiological saline with the factor of dilution 100. The plane bone scanning of rabbits showed that 99mTc-HEDTMP was principally absorbed by skeletal system. Skull, spine and legs could be observed clearly, and were more legible than the images of 99mTc-MDP. Mice trial also indicated the high bone seeking of 99mTc-HEDTMP. The skeletal uptake was 11.92% ID/g, 13.19% ID/g, 10.14% ID/g, 10.04% ID/g, 7.71% ID/g separately at 30 minutes, 1 hour, 3 hours, 6 hours and 24 hours after the injection. Kidney seemed to be the major excretory organ. The clearance of blood was quick and the retaining amount in non-target organs was small. These results indicate that 99mTc-HEDTMP can be prepared easily, and its biological properties can be compared favorably with the commonly used bone imaging agent, and it is well worth further researching as a promising potential radiopharmaceutical in nuclide diagnosis for skeleton diseases.

The effect of temperature changes on electrical performance of the betavoltaic cell

There is a significant relationship between temperature and electrical performance of a betavoltaic cell. Two silicon diodes used as energy conversion devices of betavoltaic cells were irradiated by Ni-63, and the relationships between the temperature and the electrical performance such as V(oc), I(sc), and P(max) were examined. I(sc) increased very little as temperature increased but V(oc) decreased considerably. The changing values of V(oc) were -3.1 and -3.0 mV/K, respectively, in the temperature range 233.15-333.15 K. As a result of this, P(max) and eta also decreased markedly.

Biosorption of americium-241 by Candida sp

As an important radioisotope in nuclear industry and other fields, americium-241 is one of the most serious contamination concerns duo to its high toxicity and long half-life. In this experiment, the biosorption of 241Am from solution by Candida sp., and the effects of various experimental conditions on the adsorption were investigated. The preliminary results showed that the adsorption of 241Am by Candida sp. was efficient. 241Am could be removed by Candida sp. of 0.82g/L (dry weight) from 241Am solutions of 5.6-111MBq/L (44.3-877.2μg/L)(C 0), with maximum adsorption rate (R) of 98 and maximum adsorption capacities (W) of 63.5MBq/g biomass (dry weight) (501.8μg/g). The biosorption equilibrium was achieved within 4 hour and the optimum pH was pH=2. No significant differences on 241Am adsorption were observed at 10°C–45°C, or in solutions containing Au3+ or Ag+, even 1500 times or 4500 times above the 241Am concentration, respectively. The relationship between concentrations and adsorption capacities of 241Am indicated the biosorption process should be described by a Langmuir adsorption isotherm.

Rhenium-188 labelled meso-tetrakis[3,4-bis(carboxymethyleneoxy)phenyl] porphyrin for targeted radiotherapy: preliminary biological evaluation in mice

PURPOSE

This study focusses on a promising carrier system for therapeutic and imaging purposes using meso-tetrakis[3,4-bis(carboxymethyleneoxy)phenyl] porphyrin (T(3,4)CPP). To assess its potential for clinical use, we labelled T(3,4)CPP with (188)Re and analysed some kinetic biodistribution parameters after intravenous injection in mice.

MATERIALS AND METHODS

T(3,4)CPP was synthesized and labelled with (188)Re. Normal Kunming (KM) mice and melanoma- or hepatoma-bearing BALB/c nude mice were injected intravenously with 5.55 MBq (188)Re-labelled T(3,4)CPP and sacrificed at 0.5, 2, 4, and 24 h and 8, and 24 h, respectively.

RESULTS

The (188)Re-T(3,4)CPP yield was more than 95% with specific activity 16.9 GBq (mol)(-1), and Vitamin C (VC) could increase its stability in vitro. In normal KM mice, (188)Re-T(3,4)CPP had fast blood clearance (approximately 99%, 24 h postinjection), low retention in the vital organs and hepatotropic characteristics. In nude mice, more than 4.4 and 6.1% uptake per gram of tumour (%ID g(-1)) at 8 h postinjection was in melanoma and hepatoma, respectively; this remained as high levels after 24 h as 4.6 and 6.5%, respectively. At 8 h, the tumour/blood and tumour/muscle (T/M) ratios in melanomas and hepatoma bearing mice were 7.3, 13,and 7.0, 20, respectively. Twenty-four hours later, these high ratios still continued in existence which were 9.6, 19 and 10, 25, respectively.

CONCLUSION

The results obtained in this study indicate that (188)Re-T(3,4)CPP has better tumour affinity and retainable accumulation characteristics in carcinoma which can potentially be used for tumour-targeted radiotherapy.

[Preliminarily experimental study on biological properties of 153Sm-citrate-nano-Hydroxyapatite]

OBJECTIVE

To investigate the biological character of new agent 153Sm-citrate-nano-Hydroxyapatite (nano-HA) in vitro and in vivo, and to explore a new radiopharmaceutical for the target therapy of bone metastasis cancer.

METHODS

The nano-HA was synthesized by collosol-gelatum method, and evaluated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). 153Sm was produced at a high specific activity and excellent radionuclidic purity, with which nano-HA was labeled by citrate transfer ligands in the best environment. By adopting the independent variable method, we also studied the optimally labeled condition and stability of 153Sm-citrate-nano-HA in vitro. And 153Sm-citrate-nano-HA was injected into normal rabbits for radio scanning performed. The cancer cell SMMC-7721 and MCF-7 cell lines were divided into two groups, and treated with nano-HA, 153Sm-citrate and 153Sm-citrate-nano-HA in vitro respectively, of which the cell survival rate was measured by MTT methods.

RESULTS

Through the detections of TEM, XRD showed that nano-HA consisted of needle-like microcrystals. The label rate of 153Sm-citrate-nano-HA was more than 95%, and extremely stable in vitro. The radio scanning of normal rabbits showed the skeletal system to be clear, and other systems, for example liver, spleen and kidney, could also be seen. The cell culture experiments in vitro indicated that 153Sm-citrate-nano-HA strongly inhibited the proliferation of SMMC-7721 and MCF-7 cells. 153Sm-citrate-nano-HA's half effective inhibition concentrations were 1.89 mg/L and 0.094 mg/L respectively; nano-HA's half effective inhibition concentrations were 3. 31 mg/L and 0.52 mg/L respectively; 153Sm-citrate's half effective inhibition concentrations were 4. 32 mg/L and 0. 67 mg/L respectively.

CONCLUSIONS

Sm-citrate-nano-HA shows fine biological properties, and is well worth for further researched and prepared as a promising potential radiopharmaceutical in nuclidic treatment for cancer bone metastases.

Labeling conditions, in vitro properties and biodistributions of various Sn-labeled complexes

Conditions for preparing Sn-EDTMP, Sn-DTPMP, Sn-TTHMP, Sn-HEDTMP and Sn-DTPA in aqueous solution in open air environments, and their in vitro properties including adsorption on hydroxyapatite (HA) and collagen (I) and binding to bovine serum albumin (BSA) were studied using (117m)Sn and 113Sn as tracers. Biodistributions of SnO2.xH2O.yEDTMP, SnO2.xH2O.yDTPMP, SnO2.xH2O.yTTHMP, SnO2.xH2O.yHEDTMP, SnO2.xH2O.yDTPA in normal mice were also tested. Based on the above experiments, the relationship between in vitro biochemical properties and biodistributions of these SnO2.xH2O.yLigands was investigated. The results show that Sn(IV)-Ligands are prone to hydrolysis into SnO2.xH2O.yLigands in aqueous solutions in open air environments, especially when the ligand is DTPA, when the molar ratio of metal to ligand is higher than 1:200, or when the pH of the solution is higher than 10. The in vitro experiments show that all of the SnO2.xH2O.yLigands bind strongly to BSA, and the binding percentages of SnO2.xH2O.yLigands to BSA are much higher than those of the corresponding Sn(IV)-Ligands. The biodistribution data indicate that all of the SnO2.xH2O.yLigands locate mainly in bone with little uptake in liver. When the binding percentages of SnO2.xH2O.yLigands to BSA are similar, those SnO2.xH2O.yLigands with higher adsorption on HA and collagen (I) undergo lower liver uptake.

Biosorption of americium-241 by immobilized Rhizopus arrihizus

Rhizopus arrihizus (R. arrihizus), a fungus, which in previous experiments had shown encouraging ability to remove 241Am from solutions, was immobilized by calcium alginate and other reagents. The various factors affecting 241Am biosorption by the immobilized R. arrihizus were investigated. The results showed that not only can immobilized R. arrihizus adsorb 241Am as efficiently as free R. arrihizus, but that also can be used repeatedly or continuously. The biosorption equilibrium was achieved within 2 h, and more than 94% of 241Am was removed from 241Am solutions of 1.08 MBq/l by immobilized R. arrihizu in the pH range 1-7. Temperature did not affect the adsorption on immobilized R. arrihizus in the range 15-45 degrees C. After repeated adsorption for 8 times, the immobilized R. arrihizus still adsorbed more than 97% of 241Am. At this time, the total adsorption of 241Am was more than 88.6 KBq/g, and had not yet reached saturation. Ninety-five percent of the adsorbed 241Am was desorbed by saturated EDTA solution and 98% by 2 mol/l HNO(3).