Separation of two phenotypically similar cell types via a single common marker in microfluidic channels

To isolate clinically and biologically relevant cell types from a heterogeneous population, fluorescent or magnetic tagging together with knowledge of surface biomarker profiles represents the state of the art. To date, it remains exceedingly difficult to separate phenotypically and physically similar cell types from a mixed population. We report a microfluidic platform engineered to separate two highly similar cell types using a single antibody by taking advantage of subtle variations in surface receptor density and cell size. This platform utilizes antibody-conjugated surfaces in microfluidic channels together with precise modulation of fluid shear stresses to accomplish selective fractionation in a continuous flow process. Antibody conjugation density variation on the adhesive surfaces is achieved by covalently immobilizing an antibody in the presence of poly(ethylene glycol). This platform is used to demonstrate separation of two CD31 positive cell types, human umbilical vein endothelial cells and human micro vascular endothelial cells.     

Applications of cavity ring-down spectroscopy to high precision isotope ratio measurement of 13C/12C in carbon dioxide

Recent measurements of carbon isotopes in carbon dioxide using near-infrared, diode-laser-based cavity ring-down spectroscopy (CRDS) are presented. The CRDS system achieved good precision, often better than 0.2 per thousand, for 4% CO2 concentrations, and also achieved 0.15-0.25 per thousand precision in a 78 min measurement time with cryotrap-based pre-concentration of ambient CO2 concentrations (360 ppmv). These results were obtained with a CRDS system possessing a data rate of 40 ring-downs per second and a loss measurement of 4.0 x 10(-11) cm(-1) Hz(-1/2). Subsequently, the measurement time has been reduced to under 10 min. This standard of performance would enable a variety of high concentration (3-10%) isotopic measurements, such as medical human breath analysis or animal breath experiments. The extension of this ring-down to the 2 microm region would enable isotopic analysis at ambient concentrations, which, combined with the small size, robust design, and potential for frequent measurements at a remote site, make CRDS technology attractive for remote atmospheric measurement applications.     

Monitoring/measurement of out-of-plane vibrations using shearing interferometry and interferometric grating

In this paper, an application of shear plate interferometry combined with moiré readout to monitor/measure out-of-plane vibrations is presented. Moiré fringes are produced between the fringe pattern from the shear plate and interferometric grating recorded by photographing the interference pattern generated from the shear plate. It is demonstrated that the method can be used to study periodic and non-periodic vibrations.     

Substituted benzimidazo[2,1 -h]pteridine-2,4-diones

5-Alkyl-5,6-dihydrobenzimidazo[2,1 -h]pteridine-2,4(1H,3H)-diones (4 a–d) have been synthesised by the condensation of 2-(alkyl-aminomethyl)benzimidazole dihydrochloride (1 a–d) with 5-bromobarbituric acid (2). Similarly, 5-alkyl-5,6-dihydro-4 a-nitrobenzimidazo[2,1 -h] pteridine-2,4(3H,4aH)-diones (10 a–d) have also been synthesised by the condensation of1 a–d with 5-bromo-5-nitrobarbituric acid (8) followed by cyclisation of the intermediate 5-[(benzimidazol-2-ylmethyl)alkylamino]-5-nitrobarbituric acid (9 a–d) with 5% NaOH. Thermal cyclisation of the intermediates9 a–d have also been studied. Methylation of the compound10 a has been carried out with CH₃I and K₂CO₃ usingD M F as solvent to confirm cyclisation. The structures are supported by elemental analyses, IR and PMR spectra.

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Substituierte Benzimidazo[2,1 -h]pteridin-2,4-dione

Zusammenfassung Die 5-Alkyl-5,6-dihydrobenzimidazo[2,1 -h]pteridin-2,4(1H,3H)-dione4 a-d wurden mittels Kondensation von 2-(Alkylaminomethyl)benzimidazolidhydrochloriden1 a–d mit 5-Brombarbitursäure (2) dargestellt. In ähnlicher Weise wurden die 5-Alkyl-5,6-dihydro-4a-nitrobenzimidazo[2,1 -h]pteridin-2,4(3H,4aH)-dione10 a–d über die Kondensation von1 a–d mit 5-Brom-5-nitrobarbitursäure (8) und nachfolgender Cyclisierung der intermediären 5-[(Benzimidazol-2-ylmethyl)alkylamino]-5-nitrobarbitursäuren9 a–d mit 5% NaOH dargestellt. Die thermische Cyclisierung der Produkte9 a–d wurde ebenfalls untersucht. Die Verbindungen wurden mittels Elementaranalyse, IR und PMR charakterisiert.

     

Bis(2,4–pentanedionato)vanadium(IV) aryloxides

Complexes of composition [VCl(acac)2(OAr1–4)] and [V(acac)2(OAr1–4)2] (HOAr1=HOC6H4NO2–4, HOAr2= HOC6H4OMe-4, HOAr3=HOC6H4But-4 and HOAr4= HOC6H2But-2,6–Me-4; acac=2,4–pentanedionato ion) have been synthesized by the reaction of [VCl2(acac)2] with the respective phenols or their trimethylsilyl derivatives. The complexes have been characterized by physicochemical and spectroscopic techniques. They are non-electrolytes in nitrobenzene. Room temperature magnetic moments in the 1.71–1.82B range are consistent with the VIV system. The reactions of [VCl(acac)2(OAr2)] and [VCl(acac)2(OAr3)] with chloride acceptors have been studied by conductance techniques and the formation of ionic complexes of the types [V(acac)2(OAr2,3)][MCl4] (M=Fe, Al or Sb) and [V(acac)2(OAr2,3)][MCl6] (M=P or Sb) is indicated by the conductance composition curves. Several of these complexes have been isolated and characterized.     

Microfluidic depletion of endothelial cells, smooth muscle cells, and fibroblasts from heterogeneous suspensions

Interactions between ligands and cell surface receptors can be exploited to design adhesion-based microfluidic cell separation systems. When ligands are immobilized on the microfluidic channel surfaces, the resulting cell capture devices offer the typical advantages of small sample volumes and low cost associated with microfluidic systems, with the added benefit of not requiring complex fabrication schemes or extensive operational infrastructure. Cell-ligand interactions can range from highly specific to highly non-specific. This paper describes the design of an adhesion-based microfluidic separation system that takes advantage of both types of interactions. A 3-stage system of microfluidic devices coated with the tetrapeptides arg-glu-asp-val (REDV), val-ala-pro-gly (VAPG), and arg-gly-asp-ser (RGDS) is utilized to deplete a heterogeneous suspension containing endothelial cells, smooth muscle cells, and fibroblasts. The ligand-coated channels together with a large surface area allow effective depletion of all three cell types in a stagewise manner.     

Interaction of metallic nanoparticles with a biologically active molecule, dopamine

We present the results of first-principles molecular orbital calculations describing the interaction of metallic nanoparticles, represented by Mn(13), Ag(13), and Al(13) atomic clusters, with a biologically active molecule, dopamine. The interaction strength, determined in terms of the nanoparticle-molecule complex binding energy, is found to be higher for Mn than either Ag or Al and can be explained in terms of the degree of the hybridization of the (metal) atomic orbitals with the molecular orbitals in the complex. Furthermore, smaller interaction strength of these metallic nanoparticles with water compared to that with dopamine predicts the preference of forming a complex of dopamine with the metallic nanoparticles in the aqueous solution. The calculated results may therefore suggest that the presence of these metallic nanoparticles could induce different levels of dopamine depletion in solution.     

Isolation and purification of acetylshikonin and beta-acetoxyisovalerylshikonin from cell suspension cultures of Arnebia euchroma (Royle) Johnston using rapid preparative HPLC

Shikonin and its derivatives are important red colored naphthoquinone pigments found in a large number of Arnebia species, including A. euchroma, that are responsible for the various pharmacological activities exhibited by the plant. The precise separation of each naphthoquinone is essential for total quality evaluation and bioactivity analysis of herbal formulations of A. euchroma. Furthermore, the overexploitation of this useful plant has resulted in species becoming endangered. With this in mind, a simple and rapid preparative scale HPLC method with single compound recovery for the isolation and purification of two shikonin derivatives (i. e. acetylshikonin, beta-acetoxyisovalerylshikonin) from cell suspension cultures of A. euchroma is presented. The compounds were separated on a C(18) column within 10 min using acetonitrile/methanol (95:5) as mobile phase in isocratic mode. The isolated compounds were found to be more than 98% pure. The LOD for acetylshikonin and beta-acetoxyisovalerylshikonin was estimated at 0.063 and 0.146 mug/mL, respectively, while the LOQ was found to be 0.209 and 0.487 mug/mL, respectively. The recoveries accomplished for both the shikonin derivatives were in the range of 94.7-96.8%. The repeatability, expressed as %RSD, of acetylshikonin and beta-acetoxyisovalerylshikonin was found to be 1.74 and 1.27, respectively.     

Morphology-controlled assembly of ZnO nanostructures: a bioinspired method and visible luminescence

In a bioinspired methodology, positively charged polypeptides and polyamines directly catalyse ZnO mineralization under "green" conditions of room temperature and neutral pH. The polyamines not only act as mineralizing agents for the formation of ZnO nanoparticles, but also self-assemble the nanoparticles to form spindle-like morphologies at these very ambient conditions. Both the directional growth of ZnO and its luminescent property have a pH dependency. At higher pH, the ZnO shape changes to a rodlike morphology that exhibits green photoluminescence with different intensity than that for ZnO spindles.