The effect of various cations and pH on the adsorption of U(VI) on Amberlite IR-118H resin

The effects of various metal cations and pH on the adsorption of uranium(VI) on strongly acidic cation exchanger Amberlite IR-118H (AIR-118H) were studied. The metal cations suppress U(VI) adsorption differently depending on their ionic radii. Adsorption of U(VI) on AIR-118H peaks at pH 3.4, which was attributed to the occurrence of different forms of U(VI) at different pH values. The adsorption data were then processed using the Frumkin–Fowler–Guggenheim equation, and the standard free energy of adsorption was calculated.     

Green Approach to Develop Bee Pollen-Loaded Alginate Based Nanofibrous Mat

Green electrospun materials are gaining popularity in the quest for a more sustainable environment for human life. Bee pollen (BP) is a valuable apitherapeutic product and has many beneficial features such as antioxidant and antibacterial properties. Alginate is a natural and low-cost polymer. Both natural materials show good compatibility with human tissues for biomedical applications and have no toxic effect on the environment. In this study, bee pollen-loaded sodium alginate and polyvinyl alcohol (SA/PVA) nanofibrous mats were fabricated by the electrospinning technique. The green electrospun nanofibrous mats were analyzed by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), and differential scanning calorimeter (DSC). According to the findings of the study, the toxin-free electrospinning method is suitable for producing green nanomaterial. Because of the useful properties of the bee pollen and the favorable biocompatibility of the alginate fibers, the bee pollen-loaded SA/PVA electrospun mats have the potential for use in a variety of biomedical applications.     

Analysis of the degradation of a model dental composite

Dental composites undergo material property changes during exposure to the oral environment and may release compounds of potential toxicity, such as bisphenol A. Degradation of dental composites was studied in a simplified overlayer model in which bisphenol A diglycidyl methacrylate (BisGMA) was covalently bound to a porous silicon oxide surface. It was hypothesized that the chemical structure of this overlayer would allow release of bisphenol A, BisGMA, and the decomposition products thereof, upon exposure to water for an extended period. Liquid chromatography mass spectrometry found leaching of intact BisGMA and several degradation products that contained the bisphenol A moiety from the overlayer into distilled water after 2 wks of aging. The absence of bisphenol A release from the overlayer reduces concerns regarding its potential health risk in dental composites. Nevertheless, health concerns might arise with respect to BisGMA and the leached degradation products, since they all contain the bisphenol A moiety. Abbreviations: BisGMA, bisphenol A diglycidyl methacrylate; HPLC, high-performance liquid chromatography; LCMS, liquid chromatography mass spectrometry; MA, methacrylic acid; MPS, 3-(trimethoxysilyl) propyl methacrylate; m/z, mass-to-charge ratio; and TIC, total ion chromatogram.     

Thermodynamic and kinetic investigations of uranium adsorption on amberlite IR-118H resin.

The adsorption behavior of uranium(VI) on a strongly acidic cation exchanger amberlite IR-118H has been studied as a function of the solution concentration and temperature. Results have been analyzed by Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption 7.14kJmol(-1) was calculated from the D-R adsorption isotherm. In order to understand the significance of the diffusion mechanisms and to accurately estimate the diffusivities inside the adsorbent particles, a model for uranium(VI) adsorption on amberlite IR-118H was used. The rate constants have been calculated for 293, 313 and 333K using Lagergren equation and the activation energy (E(a)) was derived using the Arhenius equation. The thermodynamic quantities for the process of adsorption have been estimated by plotting Ln K(D) versus 1/T. The DeltaH(o) and DeltaG(o) values of uranium(VI) adsorption on amberlite IR-118H show endothermic heat of adsorption; higher temperatures favor the process.     

Adsorption of uranium from aqueous solution on heat and acid treated sepiolites

In this work adsorption of uranium on natural, heat and acid treated sepiolite was studied. For acid treatment HCl and H₂SO₄ were used separately. Heat and acid treatment caused some changes in sepiolite such as surface area, micropore volume (cm³/g) and average pore diameter (Å). Different amounts of Mg ions were extracted from the lattice depending on the type of acid. After acid treatment with HCl, the amount of Mg left in the sepiolite changed a little. During H₂SO₄ treatment the sepiolite structure was progressively transformed into amorphous silica. These heat and acid treatments changed adsorption capacity and mechanism of uranium on sepiolite. Data obtained from the adsorption experiments were applied to Langmuir and Dubinin–Radushkevich (D–R) adsorption isotherms. Using these isotherms different adsorption capacities were found for natural and treated sepiolite samples. The capacity values were 3.58×10^?3, 3.14×10^?3, 2.78×10^?3 and 1.55×10^?3 mol/g for HCl treated, heat treated, natural and H₂SO₄ treated sepiolite samples, respectively. In order to evaluate the adsorption mechanism adsorption energies were calculated by the D–R isotherm. According to the adsorption energy values uranium fixed to the natural and heat treated sepiolite surface with ion exchange (12.75 and 12.12 kJ/mol, respectively). Simple physical attractions were the driving force for adsorption on HCl and H₂SO₄ treated ones (6.62 and 6.87 kJ/mol, respectively).     

Evaluation of Conformation and Association Behavior of Multivalent Alanine-Rich Polypeptides

Purpose Helical alanine-rich polypeptides with functional groups displayed along the backbone can display desired molecules such as saccharides or therapeutic molecules at a prescribed spacing. Because these polypeptides have promise for application as biomaterials, the conformation and association of these molecules have been investigated under biologically relevant conditions. Methods Three polypeptide sequences, 17-H-3, 17-H-6, and 35-H-6, have been produced through recombinant techniques. Circular dichroic (CD) spectroscopy was used to monitor the secondary structure of the polypeptides in PBS (phosphate buffered saline, pH 7.4). The aggregation behavior in PBS was monitored via analytical ultracentrifugation and non-denaturing polyacrylamide gel electrophoresis. Results The three polypeptides adopt a highly helical structure at low and ambient temperatures, and when heated, undergo a helix-to-coil transition, typical of other alanine-rich peptide sequences. The melting temperatures and van’t Hoff enthalpies, extracted from the CD data, suggest similar stability of the sequences. Although alanine-rich sequences can be prone to aggregation, there is no indication of aggregation for the three polypeptides at a range of concentrations relevant for possible biological applications. Conclusions The helical polypeptides are monomeric under biologically relevant conditions enabling application of these polypeptides as useful scaffolds for ligand or drug display. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users.     

Field-in-field IMRT versus 3D-CRT of the breast. Cardiac vessels, ipsilateral lung, and contralateral breast absorbed doses in patients with left-sided lumpectomy: a dosimetric comparison

Purpose

This study evaluated dose distribution and homogeneity of field-in-field intensity-modulated radiation treatment (FIF-IMRT) compared with standard wedged tangential-beam 3D conformal radiotherapy (CRT) of the left breast in patients who have undergone lumpectomy. Our aim was to improve dose-distribution homogeneity in the breast and decrease the dose to organs at risk (OAR), i.e, heart and vessels, ipsilateral lung, and contralateral breast.

Materials and methods

FIF-IMRT and wedge plans of 3D-CRT were carried out for 18 patients with cancer of the left breast. Plans were compared according to cumulative dose-volume histogram (c-DVH) analysis in terms of planned treatment volume (PTV), homogeneity index (HI), and conformity index (CI), as well as dose and volume parameters of OARs.

Results

When the targeted volumes receiving 105 % and 110 % of the prescribed dose in the PTV were compared, significant decreases were found with the FIF-IMRT technique. With the 105 % dose to the OARs, monitor unit (MU) counts were significantly lower with the FIF-IMRT technique. V2 of pulmonary artery, left atrium, and aorta and V1 for the contralateral breast were statistically significantly lower with FIF-IMRT plans (p = 0.001). PTV showed a better HI and CI with FIF-IMRT.

Conclusions

FIF-IMRT enables better dose distribution in the PTV and reduces dose to OARs in breast cancer radiotherapy.     

Multivalent protein polymers with controlled chemical and physical properties

In this review, we describe our work on the design, characterization, and modification of a series of alanine-rich helical polypeptides with novel functions. Glycosylation of the polypeptides has permitted investigation of polymer architecture effects on multivalent interactions. One of the members of this polypeptide family exhibits polymorphological behavior that is easily manipulated via simple changes in solution pH and temperature. Polypeptide-based fibrils formed at acidic pH and high temperature were shown to direct the one-dimensional organization of gold nanoparticles via electrostatic interactions. As a precursor to fibrils, aggregates likely comprising alanine-rich cores form at low temperatures and acidic pH and reversibly dissociate into monomers upon deprotonation. PEGylation of these polypeptides does not alter the self-association or conformational behavior of the polypeptide, suggesting potential applications in the development of assembled delivery vehicles, as modification of the polypeptides should be a useful strategy for controlling assembly.     

Antinociceptive and neurotoxicologic screening of chronic intrathecal administration of ketorolac tromethamine in the rat

Many drugs are tested intrathecally to investigate alternatives to opioids. We aimed to explore the analgesic and possible neurotoxic effects of chronic intrathecally-administered ketorolac tromethamine in rats. Catheters were placed via atlantoaxial interval in 28 Wistar rats under anesthesia of intraperitoneally-injected thiopental 30 mg/kg. Rats were randomized into 4 groups and administered 4 repeated intrathecal doses of therapy with 5-day intervals. The control group received 10 microL of saline, and the other groups received 50, 150, and 400 microg of ketorolac tromethamine respectively. The formalin test, behavioral test, and histopathological examination of four different spinal cord levels were performed. Neither behavioral testing nor histopathological examination revealed abnormalities that would suggest neurotoxicity. Formalin tests showed that both phase I and phase II responses of ketorolac tromethamine groups were significantly less than those of the control group. Although phase I responses did not differ during comparisons among ketorolac tromethamine-administered groups, phase II responses decreased significantly in groups that received 150 and 400 microg of ketorolac tromethamine. Intrathecally administered ketorolac tromethamine reduced nociceptive responses and exhibited no untoward neurological effect even at large doses. However, its intrathecal use as a safe alternative drug for chronic pain remains to be investigated in other species. IMPLICATIONS: The present study is unique because it has demonstrated that chronic intrathecal administration of ketorolac tromethamine in rats, even at considerably large doses, showed a potent analgesic effect during the formalin test without exhibiting any neurotoxic side effect.     

Kinetics of isotopic exchange between strontium polymolybdate and strontium ions in aqueous solution

A heterogeneous isotopic exchange reaction of strontium polymolybdate in strontium chloride solution was studied using ⁹⁰Sr as a tracer. The effects of low and high strontium chloride concentration on the rate and mechanism of the isotopic exchange reaction were investigated. It was found that, at high concentrations, the rate is independent of strontium concentration, but, at low concentrations, the rate is proportional to the strontium concentration. These results support a hypothesis that, at low concentrations, the rate is controlled by film diffusion, whereas at high concentrations it is controlled by particle diffusion. Experiments were performed at 293, 303 and 313 K. Activation energy of isotopic exchange reaction and thermodynamic parameters ΔH^*, ΔS^*, and ΔG^* were calculated using the Arrhenius and Eyring equations. The results also indicated that recrystallization is a predominant factor in the present exchange reaction.