"Multicolor" electrochemical labeling of DNA hybridization probes with osmium tetroxide complexes

Labeling of oligonucleotide reporter probes (RP) with electroactive markers has frequently been utilized in electrochemical detection of DNA hybridization. Osmium tetroxide complexes with tertiary amines (Os,L) bind covalently to pyrimidine (predominantly thymine) bases in DNA, forming stable, electrochemically active adducts. We propose a technique of electrochemical "multicolor" DNA coding based on RP labeling with Os,L markers involving different nitrogenous ligands (such as 2,2' -bipyridine, 1,10-phenanthroline derivatives or N,N,N',N'-tetramethylethylenediamine). At carbon electrodes the Os,L-labeled RPs produce specific signals, with the potentials of these differing depending on the ligand type. When using Os,L markers providing sufficiently large differences in their peak potentials, parallel analysis of multiple target DNA sequences can easily be performed via DNA hybridization at magnetic beads followed by voltammetric detection at carbon electrodes. Os,L labeling of oligonucleotide probes comprising a segment complementary to target DNA and an oligo(T) tail (to be modified with the osmium complex) does not require any organic chemistry facilities and can be achieved in any molecular biological laboratory. We also for the first time show that this technology can be used for labeling of oligonucleotide probes hybridizing with target DNAs that contain both purine and pyrimidine bases.     

Separation of Electrochemically Generated Ce(IV) from Rare Earths(III) in Nitric Acid Media by TBP Impregnated Resin

Abstract

Electro‐oxidation of Ce(III) to Ce(IV) in nitric acid media at different anode materials with high oxygen evolution overpotential was carried out. Ce(IV) nitrato complexes were adsorbed on a novel resin, based on porous silica beads with immobilized polystyrene/DVB copolymer, that was impregnated with tri‐n‐butyl phosphate (TBP). Under the studied conditions, Ce(IV) sorption increased with increasing nitric acid concentration (0.5–6 mol · dm^?3). Oxidation of sorbent by adsorbed Ce(IV) species resulting in Ce(III) release to the solution was observed and thoroughly evaluated. In spite of problems with TBP leakage (12%), column separation of pure Ce(IV) from Y(III) and La(III) was achieved in 6 mol · dm^?3 HNO₃ at 288 K. Ce(IV) breakthrough capacity was 0.48 mol · kg^?1‐TBP. Column regeneration with 0.1 mol · dm^?3 nitric acid yielded Ce solution with purity higher than 99.99 wt.% with respect to La and Y impurities.     

Water-born 3D nanofiber mats using cost-effective centrifugal spinning: comparison with electrospinning process: A complex study

A comparison of the electrostatic and centrifugal spinning of poly(vinyl alcohol) and poly(vinyl pyrrolidone) is shown in terms of the resulting fiber morphology and the process conditions. Specific parameters of centrifugal spinning, such rotational speed of spinneret and the relative humidity, were extensively investigated in details. Morphologies and diameters of resulting fiber mats were investigated by a scanning electron microscopy and compared between the two spinning techniques. The results revealed that formation of fibers is mainly affected by the initial polymer concentrations (and resulting viscosities) of polymeric solutions, which is in line with previous reports. However, the key novel finding of this work is that increasing relative humidity during centrifugal spinning process leads to greatly reduced fiber diameters to the levels typical for electrospinning. The obtained comparison is discussed and clearly shows technological advantages of the centrifugal spinning over electrospinning, enabling quantitative production of fibers with same or similar diameters.     

Vascular Remodeling of Clinically Used Patches and Decellularized Pericardial Matrices Recellularized with Autologous or Allogeneic Cells in a Porcine Carotid Artery Model

Background: Cardiovascular surgery is confronted by a lack of suitable materials for patch repair. Acellular animal tissues serve as an abundant source of promising biomaterials. The aim of our study was to explore the bio-integration of decellularized or recellularized pericardial matrices in vivo. Methods: Porcine (allograft) and ovine (heterograft, xenograft) pericardia were decellularized using 1% sodium dodecyl sulfate ((1) Allo-decel and (2) Xeno-decel). We used two cell types for pressure-stimulated recellularization in a bioreactor: autologous adipose tissue-derived stromal cells (ASCs) isolated from subcutaneous fat of pigs ((3) Allo-ASC and (4) Xeno-ASC) and allogeneic Wharton’s jelly mesenchymal stem cells (WJCs) ((5) Allo-WJC and (6) Xeno-WJC). These six experimental patches were implanted in porcine carotid arteries for one month. For comparison, we also implanted six types of control patches, namely, arterial or venous autografts, expanded polytetrafluoroethylene (ePTFE Propaten^® Gore^®), polyethylene terephthalate (PET Vascutek^®), chemically stabilized bovine pericardium (XenoSure^®), and detoxified porcine pericardium (BioIntegral^® NoReact^®). The grafts were evaluated through the use of flowmetry, angiography, and histological examination. Results: All grafts were well-integrated and patent with no signs of thrombosis, stenosis, or aneurysm. A histological analysis revealed that the arterial autograft resembled a native artery. All other control and experimental patches developed neo-adventitial inflammation (NAI) and neo-intimal hyperplasia (NIH), and the endothelial lining was present. NAI and NIH were most prominent on XenoSure^® and Xeno-decel and least prominent on NoReact^®. In xenografts, the degree of NIH developed in the following order: Xeno-decel > Xeno-ASC > Xeno-WJC. NAI and patch resorption increased in Allo-ASC and Xeno-ASC and decreased in Allo-WJC and Xeno-WJC. Conclusions: In our setting, pre-implant seeding with ASC or WJC had a modest impact on vascular patch remodeling. However, ASC increased the neo-adventitial inflammatory reaction and patch resorption, suggesting accelerated remodeling. WJC mitigated this response, as well as neo-intimal hyperplasia on xenografts, suggesting immunomodulatory properties.     

Electro-Oxidation of Concentrated Ce(Ⅲ) at Carbon Felt Anode in Nitric Acid Media

Electro-oxidation of Ce( Ⅲ) to Ce( Ⅳ ) in parallel plate flow type electrolyzer divided with cation exchange membrane was carried out in nitric acid media at carbon felt anode under galvanostatic conditions. Carbon felt was used as an anode for its high specific surface area and high oxygen evolution overpotential. Pt coated Ti plates were used as cathcurrent efficiency (92%) until about 80% of Ce( Ⅲ) was oxidized. Then, oxygen evolution, accompanied by terminal voltage jump, took place, lowering current efficiency. Ce( Ⅲ ) was oxidized up to 90% with current efficiency of 62%. In this mode, strong carbon felt anode oxidation was observed. The wear out of carbon felt was 46% in six consequent runs (6 h of operation). After each run, carbon felt surface had to be renewed with slightly alkaline solution to remove carbon oxidation products and ensure regular operational conditions. When anode surface was blocked, oxygen evolution took place from the beginning of electrolysis due to higher actual current density. The wear out of carbon felt anode could be minimized by means of oxygen evolution prevention. In the case when electrolysis had been stopped before oxygen evolution started (at Ce( Ⅳ ) conversion of about 80% ), the wear out of anode was less than 2% during 6 consequent runs (4 h of operation).     

Potential of houseflies to contaminate ready-to-eat food with antibiotic-resistant enterococci

It was shown previously that houseflies in fast-food restaurants commonly carry antibiotic-resistant and potentially virulent enterococci. In this study, the potential of field-collected houseflies to contaminate ready-to-eat (RTE) food with enterococci was assessed by laboratory bioassays. Houseflies were collected with a sweep net in a cattle feedlot and exposed in groups of 5, 10, 20, and 40 to a beef patty (from an RTE hamburger) for 0.5, 1.0, 3.0, and 24 h. The exposure of RTE food to flies resulted in 100% contamination with enterococci in all bioassays, regardless of the number of houseflies and the length of exposure time. In addition, with the increasing number of houseflies as well as with the increasing time exposure, the concentration of enterococci in RTE food increased. Even a short time exposure (0.5 h) resulted in food contamination, ranging from 3.1 x 10(3) CFU/g (5 houseflies) to 8.4 x 10(4) CFU/g (40 houseflies). The analysis of 23 randomly selected enterococcal isolates from RTE food after the fly exposure revealed a single species, Enterococcus faecalis. In contrast, four Enterococcus species, including E. faecalis (57.1%), E. gallinarum (19.1%), E. hirae (14.3%), and E. faecium (9.5%), represented 21 randomly selected and identified isolates from houseflies. Phenotypic screening showed that E. faecalis isolates from RTE food were resistant to ciprofloxacin (17.4%), tetracycline (13.0%), erythromycin (13.0%), and chloramphenicol (4.3%). This study demonstrates a great potential of houseflies from a cattle feedlot to contaminate RTE food with enterococci in a short time.     

Direct Spectroscopic Determination of Europium（ Ⅱ ） Concentration During Europium（ Ⅲ ） Electro-Reduction in Hydrochloric Acid Medium

Europiumis one of the most important rare earth(RE) element .It is widely used as a component ofcathode ray tubes , with screen coated with red phos-phor ,as phosphorescent pigments ,andinlaser optics .It can also be used as neutron-absorbing material .In…