Kinetic analysis of superoxide anion radical-scavenging and hydroxyl radical-scavenging activities of platinum nanoparticles

There are few reports on the physiological effects of metal nanoparticles (nps), especially with respect to their functions as scavengers for superoxide anion radical (O2(.-)) and hydroxyl radical (.OH). We tried to detect the scavenging activity of Pt nps using a hypoxanthine-xanthine oxidase system for O2(.-) and using a Fenton and a UV/H2O2 system for .OH. Electron spin resonance analysis revealed that 2 nm particle size Pt nps have the ability to scavenge O2(.-) and .OH. The calculated rate constant for the O2(.-)-scavenging reaction was 5.03 +/- 0.03 x 10(7) M (-1) s (-1). However, the analysis of the Fenton and UV/H 2O 2 system in the presence of Pt nps suggested that the .OH-scavenging reaction cannot be determined in both systems. Among particle sizes tested from 1 to 5 nm, 1 nm Pt nps showed the highest O2(.-)-scavenging ability. Almost no cytotoxicity was observed even after adherent cells (TIG-1, HeLa, HepG2, WI-38, and MRC-5) were exposed to Pt nps at concentrations as high as 50 mg/L. Pt nps scavenged intrinsically generated reactive oxygen species (ROS) in HeLa cells. Additionally, Pt nps significantly reduced the levels of intracellular O2(.-) generated by UVA irradiation and subsequently protected HeLa cells from ROS damage-induced cell death. These findings suggest that Pt nps may be a new type of antioxidant capable of circumventing the paradoxical effects of conventional antioxidants.     

Integrating sensitive quantification of hepatic metabolic functions by capillary electrophoresis with laser-induced fluorescence detection

We report the establishment of capillary electrophoresis with laser-induced fluorescence (CE-LIF) detection as a common analytical platform for sensitive quantification of both phase I and II metabolism in various hepatic in vitro models.     

A novel 3D mammalian cell perfusion-culture system in microfluidic channels

Mammalian cells cultured on 2D surfaces in microfluidic channels are increasingly used in drug development and biological research applications. These systems would have more biological or clinical relevance if the cells exhibit 3D phenotypes similar to the cells in vivo. We have developed a microfluidic channel based system that allows cells to be perfusion-cultured in 3D by supporting them with adequate 3D cell-cell and cell-matrix interactions. The maximal cell-cell interaction was achieved by perfusion-seeding cells through an array of micropillars; and 3D cell-matrix interactions were achieved by a polyelectrolyte complex coacervation process to form a thin layer of matrix conforming to the 3D cell shapes. Carcinoma cell lines (HepG2, MCF7), primary differentiated (hepatocytes) and primary progenitor cells (bone marrow mesenchymal stem cells) were perfusion-cultured for 72 hours to 1 week in the microfluidic channel, which preserved their 3D cyto-architecture and cell-specific functions or differentiation competence. This transparent 3D microfluidic channel-based cell culture system also allows direct optical monitoring of cellular events for a wide range of applications.     

Ultra-performance liquid chromatography/time-of-flight mass spectrometry based metabolomics of raw and steamed Panax notoginseng

At present, metabolite profiling is of growing importance in herbal medicine fields such as breeding, formulation, quality control and clinical trials. This preliminary study indicated that ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOFMS)-based metabolomics allows direct detection of down-stream derivatives of metabolites, arising from the herbal formulation process. This analytical approach allows the discrimination and tentative authentication of unique biomarkers related to different herbal extracts using unsupervised multivariate principal component analysis (PCA). The tentative identification of biomarkers is complemented significantly by the accurate mass measurement of TOFMS and the high resolution and high retention time reproducibility rendered by UPLC. The application of this approach in herbal extract discrimination and ginsenoside biomarker discovery of raw and steamed Panax notoginseng (Burk.) F.H. Chen is demonstrated and discussed.     

Purity of rubrene single crystals

Liquid chromatography connected with mass spectroscopy reveals that the oxidized form of rubrene is the major impurity in commercial powder of rubrene as well as in rubrene single crystals. One form of rubrene impurity can be transformed into the other. In solution, rubrene undergoes photo-oxidation completely until the red color of the rubrene solution disappears. Single crystals, due to compact packing of molecules and the required molecular shape change during oxidation, oxidize only on the surface.     

Study of the vi13/2-1 band in 189Pt

High-spin levels of 189Pt have been studied with the in-beam γ-spectroscopy method via the 176Yb(18O,5n) reaction at the beam energies of 88 and 95 MeV. The previously known vi13/2-1 band has been confirmed, and its unfavored signature branch extended up to the 31/2+ state. Within the framework of the triaxial particle-rotor model, the vi13/2-1 band is suggested to be associated with the 11/2[615] configuration, and to have triaxial deformation.     

Two-dimensional fluorescence difference gel electrophoresis for comparison of affinity and non-affinity based downstream processing of recombinant monoclonal antibody

Although Staphylococcus Protein A (SpA) affinity chromatography is the state of the art capture step for antibody purification, non-affinity methods are more economical. We used two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) to evaluate the purification of a recombinant IgG₁ antibody from cultured cells, with two different processes: (1) SpA capture followed by cation-exchange chromatography (CEX); and (2) CEX capture, followed by anion exchanger, then hydrophobic interaction chromatography. Efficiencies were similar in sodium dodecylsulphate polyacrylamide gel electrophoresis and size-exclusion chromatography; however, 2-D DIGE revealed higher efficiency with SpA than with CEX capture. Thus, 2-D DIGE is a valuable tool for downstream process development.     

Sensitive detection of potassium ion using Prussian blue nanotube sensor

A model K⁺ sensor using Prussian blue nanotubes is fabricated by electrochemical deposition of Prussian blue (PB) within the nanochannels of a porous metal-coated membrane with partially covered pore openings. The PB nanotube sensor exhibits excellent stability giving reproducible peak potentials up to 500 measurement cycles, a very low detection limit of 2.0 × 10⁻⁸ M and extremely wide logarithmic linear ranges between 5.0 × 10⁻⁸–7.0 × 10⁻⁴ M and 7.0 × 10⁻⁴–1.0 M. Negligible interferences by Na⁺, Mg²⁺ and Ca²⁺ are observed and a rapid analysis time of 30 s is readily achieved. The ease of electrodeposition, high stability of PB nanotubes and outstanding analytical performance which surpasses conventional PB voltammetric and potentiometric sensors demonstrates potential sensing applications including ion sensors and biosensors using PB and other metal hexacyanoferrate nanotubes.     

Large area impingement spray cooling from multiple normal and inclined spray nozzles

An inclined spray chamber with four multiple nozzles to cool a 1 kW 6U electronic test card has been designed and tested in this study. The multiple inclined sprays can cover the same heated surface area as that with the multiple normal sprays but halve the volume of the spray chamber. The spray cooling system used R134a as a working fluid in a modified refrigeration cycle. It is observed that increasing mass flow rate and pressure drop across the nozzles improved the heat transfer coefficient with a maximum enhancement of 117 %, and reduced the maximum temperature difference at the heated surface from 13.8 to 8.4 °C in the inclined spray chamber with a heat flux of 5.25 W/cm², while the heat transfer coefficient of the normal spray increased with a maximum enhancement of 215 % and the maximum temperature difference decreased from 10.8 to 5.4 °C under similar operating conditions. We conclude that the multiple inclined sprays could produce a higher heat transfer coefficient but with an increase in non-uniformity of the surface temperature compared with the multiple normal sprays.     

Nanosize-induced drastic drop in equilibrium hydrogen pressure for hydride formation and structural stabilization in pd-rh solid-solution alloys

We have synthesized and characterized homogeneous solid-solution alloy nanoparticles of Pd and Rh, which are immiscible with each other in the equilibrium bulk state at around room temperature. The Pd-Rh alloy nanoparticles can absorb hydrogen at ambient pressure and the hydrogen pressure of Pd-Rh alloys for hydrogen storage is dramatically decreased by more than 4 orders of magnitude from the corresponding pressure in the metastable bulk state. The solid-solution state is still maintained in the nanoparticles even after hydrogen absorption/desorption, in contrast to the metastable bulks which are separated into Pd and Rh during the process.