Science.gov

Sample records for dielectrophoretic field-flow fractionation

  1. Numerical simulation of bioparticle separation by dielectrophoretic field-flow-fractionation (DEP-FFF)

    NASA Astrophysics Data System (ADS)

    Marchis, Andreea; Neculae, Adrian

    2014-11-01

    The separation systems based on dielectrophoretic field-flow-fractionation (DEP-FFF) are used for a wide range of bioparticle types, including cells, bacteria, viruses, proteins, etc. An array of interdigitated microelectrodes lining the bottom surface of a thin chamber is used to generate dielectrophoretic forces that levitate the bioparticle mixture. The balance between DEP levitation and gravitational forces determines the bioparticles position at equilibrium heights within a fluid-flow profile, and consequently determines their velocities and the corresponding elution times. The elution time depends on the voltage applied on the microelectrodes, geometry of the device, bioparticle dielectric properties and density. This paper analyses numerically the behavior of a bioparticle mixture suspended in a dense and viscous fluid under dielectrophoresis. The controlled spatial separation of bioparticle mixture is performed by a combination of dielectrophoretic and hydrodynamic forces. The theoretical background and a set of numerical results (calculated DEP force, particle trajectories, etc.) are presented. The numerical solutions are obtained using the COMSOL Multiphysics finite element solver. The presented results demonstrate that the DEP-FFF method can be successfully applicable to many biomedical cell separation problems, including microfluidic-scale diagnosis and preparative-scale purification of cell subpopulations.

  2. Enrichment of putative stem cells from adipose tissue using dielectrophoretic field-flow fractionation

    PubMed Central

    Vykoukal, Jody; Vykoukal, Daynene M.; Freyberg, Susanne; Alt, Eckhard U.; Gascoyne, Peter R. C.

    2009-01-01

    We have applied the microfluidic cell separation method of dielectrophoretic field-flow fractionation (DEP-FFF) to the enrichment of a putative stem cell population from an enzyme-digested adipose tissue derived cell suspension. A DEP-FFF separator device was constructed using a novel microfluidic-microelectronic hybrid flex-circuit fabrication approach that is scaleable and anticipates future low-cost volume manufacturing. We report the separation of a nucleated cell fraction from cell debris and the bulk of the erythrocyte population, with the relatively rare (<2% starting concentration) NG2-positive cell population (pericytes and/or putative progenitor cells) being enriched up to 14-fold. This work demonstrates a potential clinical application for DEP-FFF and further establishes the utility of the method for achieving label-free fractionation of cell subpopulations. PMID:18651083

  3. Dielectrophoretic Field-Flow Fractionation System for Detection of Aquatic Toxicants

    PubMed Central

    Pui-ock, Sittisak; Ruchirawat, Mathuros; Gascoyne, Peter

    2009-01-01

    Dielectrophoretic field-flow fractionation (dFFF) was applied as a contact-free way to sense changes in the plasma membrane capacitances and conductivities of cultured human HL-60 cells in response to toxicant exposure. A micropatterned electrode imposed electric forces on cells in suspension in a parabolic flow profile as they moved through a thin chamber. Relative changes in the dFFF peak elution time, reflecting changes in cell membrane area and ion permeability, were measured as indices of response during the first 150 min of exposure to eight toxicants having different single or mixed modes of action (acrylonitrile, actinomycin D, carbon tetrachloride, endosulfan, N-nitroso-N-methylurea (NMU), paraquat dichloride, puromycin, and styrene oxide). The dFFF method was compared with the cell viability assay for all toxicants and with the mitochondrial potentiometric dye assay or DNA alkaline comet assay according to the mode of action of the specific agents. Except for low doses of nucleic acid-targeting agents (actinomycin D and NMU), the dFFF method detected all toxicants more sensitively than other assays, in some cases up to 105 times more sensitively than the viability approach. The results suggest the dFFF method merits additional study for possible applicability in toxicology. PMID:18788754

  4. Dynamic physical properties of dissociated tumor cells revealed by dielectrophoretic field-flow fractionation

    PubMed Central

    Shim, Sangjo; Gascoyne, Peter; Noshari, Jamileh; Stemke Hale, Katherine

    2013-01-01

    Metastatic disease results from the shedding of cancer cells from a solid primary tumor, their transport through the cardiovascular system as circulating tumor cells (CTCs) and their engraftment and growth at distant sites. Little is known about the properties and fate of tumor cells as they leave their growth site and travel as single cells. We applied analytical dielectrophoretic field-flow fractionation (dFFF) to study the membrane capacitance, density and hydrodynamic properties together with the size and morphology of cultured tumor cells after they were harvested and placed into single cell suspensions. After detachment, the tumor cells exhibited biophysical properties that changed with time through a process of cytoplasmic shedding whereby membrane and cytoplasm were lost. This process appeared to be distinct from the cell death mechanisms of apoptosis, anoikis and necrosis and it may explain why multiple phenotypes are seen among CTCs isolated from patients and among the tumor cells obtained from ascitic fluid of patients. The implications of dynamic biophysical properties and cytoplasmic loss for CTC migration into small blood vessels in the circulatory system, survival and gene expression are discussed. Because the total capacitance of tumor cells remained higher than blood cells even after they had shed cytoplasm, dFFF offers a compelling, antibody-independent technology for isolating viable CTCs from blood even when they are no larger than peripheral blood mononuclear cells. PMID:21691666

  5. Separation of polystyrene microbeads using dielectrophoretic/gravitational field-flow-fractionation.

    PubMed Central

    Wang, X B; Vykoukal, J; Becker, F F; Gascoyne, P R

    1998-01-01

    The characterization of a dielectrophoretic/gravitational field-flow-fractionation (DEP/G-FFF) system using model polystyrene (PS) microbeads is presented. Separations of PS beads of different surface functionalization (COOH and none) and different sizes (6, 10, and 15 microm in diameter) are demonstrated. To investigate the factors influencing separation performance, particle elution times were determined as a function of particle suspension conductivity, fluid flow rate, and applied field frequency and voltage. Experimental data were analyzed using a previously reported theoretical model and good agreement between theory and experiment was found. It was shown that separation of PS beads was based on the differences in their effective dielectric properties. Particles possessing different dielectric properties were positioned at different heights in a fluid-flow profile in a thin chamber by the balance of DEP and gravitational forces, transported at different velocities under the influence of the fluid flow, and thereby separated. To explore hydrodynamic (HD) lift effects, velocities of PS beads were determined as a function of fluid flow rate in the separation chamber when no DEP field was applied. In this case, particle equilibrium height positions were governed solely by the balance of HD lift and gravitational forces. It was concluded that under the experimental conditions reported here, the DEP force was the dominant factor in controlling particle equilibrium height and that HD lift force played little role in DEP/G-FFF operation. Finally, the influence of various experimental parameters on separation performance was discussed for the optimization of DEP/G-FFF. PMID:9591693

  6. Model-based analysis of a dielectrophoretic microfluidic device for field-flow fractionation.

    PubMed

    Mathew, Bobby; Alazzam, Anas; Abutayeh, Mohammad; Stiharu, Ion

    2016-08-01

    We present the development of a dynamic model for predicting the trajectory of microparticles in microfluidic devices, employing dielectrophoresis, for Hyperlayer field-flow fractionation. The electrode configuration is such that multiple finite-sized electrodes are located on the top and bottom walls of the microchannel; the electrodes on the walls are aligned with each other. The electric potential inside the microchannel is described using the Laplace equation while the microparticles' trajectory is described using equations based on Newton's second law. All equations are solved using finite difference method. The equations of motion account for forces including inertia, buoyancy, drag, gravity, virtual mass, and dielectrophoresis. The model is used for parametric study; the geometric parameters analyzed include microparticle radius, microchannel depth, and electrode/spacing lengths while volumetric flow rate and actuation voltage are the two operating parameters considered in the study. The trajectory of microparticles is composed of transient and steady state phases; the trajectory is influenced by all parameters. Microparticle radius and volumetric flow rate, above the threshold, do not influence the steady state levitation height; microparticle levitation is not possible below the threshold of the volumetric flow rate. Microchannel depth, electrode/spacing lengths, and actuation voltage influence the steady-state levitation height. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Field-Flow Fractionation.

    ERIC Educational Resources Information Center

    Caldwell, Karin D.

    1988-01-01

    Describes a technique for separating samples that range over 15 orders of magnitude in molecular weight. Discusses theory, apparatus, and sample preparation techniques. Lists several types of field-flow fractionation (FFF) and their uses: sedimentation FFF, thermal FFF, flow FFF, electrical FFF, and steric FFF. (ML)

  8. Dielectrophoretic field-flow method for separating particle populations in a chip with asymmetric electrodes

    PubMed Central

    Iliescu, Ciprian; Tresset, Guillaume; Xu, Guolin

    2009-01-01

    This paper presents a field-flow method for separating particle populations in a dielectrophoretic (DEP) chip with asymmetric electrodes under continuous flow. The structure of the DEP device (with one thick electrode that defines the walls of the microfluidic channel and one thin electrode), as well as the fabrication and characterization of the device, was previously described. A characteristic of this structure is that it generates an increased gradient of electric field in the vertical plane that can levitate the particles experiencing negative DEP. The separation method consists of trapping one population to the bottom of the microfluidic channel using positive DEP, while the other population that exhibits negative DEP is levitated and flowed out. Viable and nonviable yeast cells were used for testing of the separation method. PMID:20216966

  9. Introducing dielectrophoresis as a new force field for field-flow fractionation.

    PubMed Central

    Huang, Y; Wang, X B; Becker, F F; Gascoyne, P R

    1997-01-01

    We present the principle of cell characterization and separation by dielectrophoretic field-flow fractionation and show preliminary experimental results. The operational device takes the form of a thin chamber in which the bottom wall supports an array of microelectrodes. By applying appropriate AC voltage signals to these electrodes, dielectrophoretic forces are generated to levitate cells suspended in the chamber and to affect their equilibrium heights. A laminar flow profile is established in the chamber so that fluid flows faster with increasing distance from the chamber walls. A cell carried in the flow stream will attain an equilibrium height, and a corresponding velocity, based on the balance of dielectrophoretic, gravitational, and hydrodynamic lift forces it experiences. We describe a theoretical model for this system and show that the cell velocity is a function of the mean fluid velocity, the voltage and frequency of the signals applied to the electrodes, and, most significantly, the cell dielectric properties. The validity of the model is demonstrated with human leukemia (HL-60) cells subjected to a parallel electrode array, and application of the device to separating HL-60 cells from peripheral blood mononuclear cells is shown. PMID:9251828

  10. Field-flow fractionation of chromosomes

    SciTech Connect

    Giddings, J.C.

    1991-09-01

    The work done on this project is divided into two principal areas. The first involves the application of sedimentation/steric FFF to metaphase chromosomes in an attempt to fractionate the chromosomes according to their size. The preparation of chromosomes from a number of organisms was attempted; procedures were finally worked out in collaboration with Los Alamos National Laboratory for the preparation of metaphase chromosomes from Chinese hamster cells. After extensive experimental work was done to identify suitable operating conditions, the partial fractionation of the Chinese hamster chromosomes was achieved. In the second component of the project, flow FFF was applied to the separation of DNA fragments. Figures are provided that show considerable success in the separation of plasmid digests and in the separation of single from double stranded DNA under 10{sup 4} base pairs. Preliminary work was done on DNA fragments having a size greater than 10{sup 4} base pairs. This work has served to establish the inversion point for DNA.

  11. Field-flow fractionation: addressing the nano challenge.

    PubMed

    Williams, S Kim Ratanathanawongs; Runyon, J Ray; Ashames, Akram A

    2011-02-01

    Field-flow fractionation is coming of age as a family of analytical methods for separating and characterizing macromolecules, nanoparticles, and particulates. The capabilities and versatility of these techniques are discussed in light of the challenges that are being addressed in analyzing nanometer-sized sample components and the insights gained through their use in applications ranging from materials science to biology. (To listen to a podcast about this feature, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html .).

  12. Field-Flow Fractionation of Carbon Nanotubes and Related Materials

    SciTech Connect

    John P. Selegue

    2011-11-17

    During the grant period, we carried out FFF studies of carbonaceous soot, single-walled and multi-walled carbon nanotubes, carbon nano-onions and polyoxometallates. FFF alone does not provide enough information to fully characterize samples, so our suite of characterization techniques grew to include light scattering (especially Photon Correlation Spectroscopy), scanning and transmission electron microscopy, thermogravimetric analysis and spectroscopic methods. We developed convenient techniques to deposit and examine minute FFF fractions by electron microscopy. In collaboration with Arthur Cammers (University of Kentucky), we used Flow Field-Flow Fractionation (Fl-FFF) to monitor the solution-phase growth of keplerates, a class of polyoxometallate (POM) nanoparticles. We monitored the evolution of Mo-POM nanostructures over the course of weeks by by using flow field-flow fractionation and corroborated the nanoparticle structures by using transmission electron microscopy (TEM). Total molybdenum in the solution and precipitate phases was monitored by using inductively coupled plasma analyses, and total Mo-POM concentration by following the UV-visible spectra of the solution phase. We observe crystallization-driven formation of (Mo132) keplerate and solution phase-driven evolution of structurally related nanoscopic species (3-60 nm). FFF analyses of other classes of materials were less successful. Attempts to analyze platelets of layered materials, including exfoliated graphite (graphene) and TaS2 and MoS2, were disappointing. We were not able to optimize flow conditions for the layered materials. The metal sulfides react with the aqueous carrier liquid and settle out of suspension quickly because of their high density.

  13. Gravitational field-flow fractionation of human hemopoietic stem cells.

    PubMed

    Roda, Barbara; Reschiglian, Pierluigi; Alviano, Francesco; Lanzoni, Giacomo; Bagnara, Gian Paolo; Ricci, Francesca; Buzzi, Marina; Tazzari, Pier Luigi; Pagliaro, Pasqualepaolo; Michelini, Elisa; Roda, Aldo

    2009-12-25

    New cell sorting methodologies, which are simple, fast, non-invasive, and able to isolate homogeneous cell populations, are needed for applications ranging from gene expression analysis to cell-based therapy. In particular, in the forefront of stem cell isolation, progenitor cells have to be separated under mild experimental conditions from complex heterogeneous mixtures prepared from human tissues. Most of the methodologies now employed make use of immunological markers. However, it is widely acknowledged that specific markers for pluripotent stem cells are not as yet available, and cell labelling may interfere with the differentiation process. This work presents for the first time gravitational field-flow fractionation (GrFFF), as a tool for tag-less, direct selection of human hematopoietic stem and progenitor cells from cell samples obtained by peripheral blood aphaeresis. These cells are responsible to repopulate the hemopoietic system and they are used in transplantation therapies. Blood aphaeresis sample were injected into a GrFFF system and collected fractions were characterized by flow cytometry for CD34 and CD45 expression, and then tested for viability and multi-differentiation potential. The developed GrFFF method allowed obtaining high enrichment levels of viable, multi-potent hematopoietic stem cells in specific fraction and it showed to fulfil major requirements of analytical performance, such as selectivity and reproducibility of the fractionation process and high sample recovery.

  14. Autophagic subpopulation sorting by sedimentation field-flow fractionation.

    PubMed

    Naves, Thomas; Battu, Serge; Jauberteau, Marie-Odile; Cardot, Philippe J P; Ratinaud, Marie-Hélène; Verdier, Mireille

    2012-10-16

    The development of hypoxic areas often takes place in solid tumors and leads cells to undergo adaptive signalization like autophagy. This process is responsible for misfolded or aggregated proteins and nonfunctional organelle recycling, allowing cells to maintain their energetic status. However, it could constitute a double-edged pathway leading to both survival and cell death. So, in response to stress such as hypoxia, autophagic and apoptotic cells are often mixed. To specifically study and characterize autophagic cells and the process, we needed to develop a method able to (1) isolate autophagic subpopulation and (2) respect apoptotic and autophagic status. Sedimentation field-flow fractionation (SdFFF) was first used to monitor physical parameter changes due to the hypoxia mimetic CoCl(2) in the p53 mutated SKNBE2(c) human neuroblastoma cell line. Second, we showed that "hyperlayer" elution is able to prepare autophagic enriched populations, fraction (F3), overexpressing autophagic markers (i.e., LC3-II accumulation and punctiform organization of autophagosomes as well as cathepsin B overactivity). Conversely, the first eluted fraction exhibited apoptotic markers (caspase-3 activity and Bax increased expression). For the first time, SdFFF was employed as an analytical tool in order to discriminate apoptotic and autophagic cells, thus providing an enriched autophagic fraction consecutively to a hypoxic stress.

  15. Sedimentation field flow fractionation monitoring of bimodal wheat starch amylolysis.

    PubMed

    Salesse, C; Battu, S; Begaud-Grimaud, G; Cledat, D; Cook-Moreau, J; Cardot, P J P

    2006-10-06

    Enzymatic starch granule hydrolysis is one of the most important reactions in many industrial processes. In this study, we investigated the capacity of sedimentation field flow fractionation (SdFFF) to monitor the amylolysis of a bimodal starch population: native wheat starch. Results demonstrated a correlation between fractogram changes and enzymatic hydrolysis. Furthermore, SdFFF was used to sort sub-populations which enhanced the study of granule size distribution changes occurring during amylolysis. These results show the interest in coupling SdFFF with particle size measurement methods to study complex starch size/density modifications associated to hydrolysis. These results suggested different applications such as the association of SdFFF with structural investigations to better understand the specific mechanisms of amylolysis or starch granule structure.

  16. Field flow fractionation techniques to explore the "nano-world".

    PubMed

    Contado, Catia

    2017-04-01

    Field flow fractionation (FFF) techniques are used to successfully characterize several nanomaterials by sizing nano-entities and producing information about the aggregation/agglomeration state of nanoparticles. By coupling FFF techniques to specific detectors, researchers can determine particle-size distributions (PSDs), expressed as mass-based or number-based PSDs. This review considers FFF applications in the food, biomedical, and environmental sectors, mostly drawn from the past 4 y. It thus underlines the prominent role of asymmetrical flow FFF within the FFF family. By concisely comparing FFF techniques with other techniques suitable for sizing nano-objects, the advantages and the disadvantages of these instruments become clear. A consideration of select recent publications illustrates the state of the art of some lesser-known FFF techniques and innovative instrumental set-ups.

  17. Human lymphocyte sorting by gravitational field-flow fractionation.

    PubMed

    Roda, Barbara; Reschiglian, Pierluigi; Zattoni, Andrea; Tazzari, Pier Luigi; Buzzi, Marina; Ricci, Francesca; Bontadini, Andrea

    2008-09-01

    Interest in biological studies on various cell types for many biomedical applications, from research to patient treatments, is constantly increasing. The ability to discriminate (sort) and/or quantify distinct subpopulations of cells has become increasingly important. For instance, not only detection but also the highest depletion of neoplastic cells from normal cells is an important requisite in the autologous transplantation of lymphocytes for blood cancer treatments. In this work, gravitational field-flow fractionation (GrFFF) is shown to be effective for sorting a heterogeneous mixture of human, living lymphocytes constituted of neoplastic B cells from a Burkitt lymphoma cell line and healthy T and B lymphocytes from blood samples. GrFFF does not require the use of fluorescent immunotags for sorting cells, and the sorted cells can be collected for their further characterization. Flow cytometry was used to assess the viability of the cells collected, and to evaluate the cell fractionation achieved. A low amount of neoplastic B lymphocytes (less than 2%) was found in a specific fraction obtained by GrFFF. The high depletion from neoplastic cells (more than 98%) was confirmed by a clonogenicity test.

  18. Field_flow Fractionation For The Characterisation of Natural Colloids

    NASA Astrophysics Data System (ADS)

    von der Kammer, F.; Saal, C.; Baborowski, M.

    The investigation of colloid contribution to transport processes requires a detailed analysis of the actually and potentially mobile colloidal phases present in a certain system of interest. In general all important parameters can not be determined with a single method. Field Flow Fractionation (FFF) is considered as a powerful technique regarding the analysis of colloid molecular weight or size-distributions. FFF can be labelled as a hydrodynamic chromatography that provides a fractionation of an usu- ally aqueous colloid dispersion due to the selective retention of particles/colloids in a ribbon shaped channel. The retention ratios of particles are depending on particle volume, density or diffusion coefficient, depending on the type of channel and method used. In contrast to methods like size exclusion chromatography, the absence of a sta- tionary phase enables FFF to cover a particle size range of theoretically five orders of magnitude (0.001 to 100 µm) and provides the analysis even of fragile aggregates. FFF equipped with modern detection systems like on-line (or quasi-on-line) static or dynamic light scattering detectors provide an internal verification of the fractionation itself and methods to retrieve the particles mean shape factor from the combination of different fractionation/detection methods are in development. Moreover, regarding the light scattering techniques, FFF provides close to monodisperse sample slices, enabling the scattering techniques to work at optimal conditions even with broad dis- tributed samples. ICP-detectors provide main and trace element distributions over par- ticle size. The presentation will give a critical overview of the application of advanced FFF methods on natural colloidal samples, covering Flow-FFF, Sedimentation-FFF and hyphenated methods using static and dynamic light scattering, UV-VIS and fluo- rescence detection as well as ICP-MS couplings.

  19. Coating microchannels to improve Field-Flow Fractionation

    NASA Astrophysics Data System (ADS)

    Shendruk, Tyler N.; Slater, Gary W.

    2011-03-01

    We propose a selective-steric-mode Field-Flow Fractionation (ssFFF) technique for size separation of particles. Grafting a dense polymer brush onto the accumulation wall of a microchannel adds two novel effects to FFF: the particles must pay an entropic cost to enter the brush and the brush has a hydrodynamic thickness that shifts the no-slip condition. For small particles, the brush acts as a low-velocity region, leading to chromatographic-like retention. We present an analytical retention theory for small but finite-sized particles in a microchannel with a dense Alexander brush coating that possesses a well-defined hydrodynamic thickness. This theory is compared to a numerical solution for the retention ratio given by a flow approximated by the Brinkman equation and particle-brush interaction that is both osmotic and compressional. Large performance improvements are predicted in several regimes. Multi-Particle Collision simulations of the system assess the impact of factors neglected by the theory such as the dynamics of particle impingement on the brush subject to a flow.

  20. Paper-based flow fractionation system for preconcentration and field-flow fractionation.

    NASA Astrophysics Data System (ADS)

    Hong, Seokbin; Kwak, Rhokyun; Kim, Wonjung

    2015-11-01

    We present a novel paper-based flow fractionation system for preconcentration and field-flow fractionation. The paper fluidic system consisting of a straight channel connected with expansion regions can generate a fluid flow with a constant flow rate for 10 min without any external pumping devices. The flow bifurcates with a fraction ratio of up to 30 depending on the control parameters of the channel geometry. Utilizing this simple paper-based bifurcation system, we developed a continuous-flow preconcentrator and a field-flow fractionator on a paper platform. Our experimental results show that the continuous-flow preconcentrator can produce a 33-fold enrichment of the ion concentration and that the flow fractionation system successfully separates the charged dyes. Our study suggests simple, cheap ways to construct preconcentration and field-flow fractionation systems for paper-based microfluidic diagnostic devices. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP) (NRF-2015R1A2A2A04006181).

  1. Illustrating Some Principles of Separation Science through Gravitational Field-Flow Fractionation

    ERIC Educational Resources Information Center

    Beckett, Ronald; Sharma, Reshmi; Andric, Goja; Chantiwas, Rattikan; Jakmunee, Jaroon; Grudpan, Kate

    2007-01-01

    Particle separation is an important but often neglected topic in undergraduate curricula. This article discusses how the method of gravitational field-flow fractionation (GrFFF) can be used to illustrate many principles of separation science and some fundamental concepts of physical chemistry. GrFFF separates particles during their elution through…

  2. Illustrating Some Principles of Separation Science through Gravitational Field-Flow Fractionation

    ERIC Educational Resources Information Center

    Beckett, Ronald; Sharma, Reshmi; Andric, Goja; Chantiwas, Rattikan; Jakmunee, Jaroon; Grudpan, Kate

    2007-01-01

    Particle separation is an important but often neglected topic in undergraduate curricula. This article discusses how the method of gravitational field-flow fractionation (GrFFF) can be used to illustrate many principles of separation science and some fundamental concepts of physical chemistry. GrFFF separates particles during their elution through…

  3. Coupling gravitational and flow field-flow fractionation, and size-distribution analysis of whole yeast cells.

    PubMed

    Sanz, Ramsés; Puignou, Lluís; Galceran, Maria Teresa; Reschiglian, Pierluigi; Zattoni, Andrea; Melucci, Dora

    2004-08-01

    This work continues the project on field-flow fractionation characterisation of whole wine-making yeast cells reported in previous papers. When yeast cells are fractionated by gravitational field-flow fractionation and cell sizing of the collected fractions is achieved by the electrosensing zone technique (Coulter counter), it is shown that yeast cell retention depends on differences between physical indexes of yeast cells other than size. Scanning electron microscopy on collected fractions actually shows co-elution of yeast cells of different size and shape. Otherwise, the observed agreement between the particle size distribution analysis obtained by means of the Coulter counter and by flow field-flow fractionation, which employs a second mobile phase flow as applied field instead of Earth's gravity, indicates that yeast cell density can play a major role in the gravitational field-flow fractionation retention mechanism of yeast cells, in which flow field-flow fractionation retention is independent of particle density. Flow field-flow fractionation is then coupled off-line to gravitational field-flow fractionation for more accurate characterisation of the doubly-fractionated cells. Coupling gravitational and flow field-flow fractionation eventually furnishes more information on the multipolydispersity indexes of yeast cells, in particular on their shape and density polydispersity.

  4. Asymmetrical flow field-flow fractionation of white wine chromophoric colloidal matter.

    PubMed

    Coelho, Christian; Parot, Jérémie; Gonsior, Michael; Nikolantonaki, Maria; Schmitt-Kopplin, Philippe; Parlanti, Edith; Gougeon, Régis D

    2017-04-01

    Two analytical separation methods-size-exclusion chromatography and asymmetrical flow field-flow fractionation-were implemented to evaluate the integrity of the colloidal composition of Chardonnay white wine and the impact of pressing and fermentations on the final macromolecular composition. Wine chromophoric colloidal matter, representing UV-visible-absorbing wine macromolecules, was evaluated by optical and structural measurements combined with the description of elution profiles obtained by both separative techniques. The objective of this study was to apply these two types of fractionation on a typical Chardonnay white wine produced in Burgundy and to evaluate how each of them impacted the determination of the macromolecular chromophoric content of wine. UV-visible and fluorescence measurements of collected fractions were successfully applied. An additional proteomic study revealed that grape and microorganism proteins largely impacted the composition of chromophoric colloidal matter of Chardonnay wines. Asymmetrical flow field-flow fractionation appeared to be more reliable and less invasive with respect to the native chemical environment of chromophoric wine macromolecules, and hence is recommended as a tool to fractionate chromophoric colloidal matter in white wines. Graphical Abstract An innovative macromolecular separation method based on Asymmetrical Flow Field-Flow Fractionation was developed to better control colloidal dynamics across Chardonnay white winemaking.

  5. Modification of glass channel walls for separation of biological particles by gravitational field-flow fractionation.

    PubMed

    Plocek, J; Konecný, P; Chmelík, J

    1994-06-17

    In the gravitational field-flow fractionation of complex samples, various interaction and adsorption phenomena can occur in separation channels that influence fractionation and complicate the explanation of resulting fractograms. To overcome these problems, the glass surface was modified to create charge-free, non-adsorbing hydrophilic media for the mild treatment of hydrophilic biological particles. The modification was carried out in two steps: (1) by a simple lacquering of the glass surface with polystyrene diluted in toluene and (2) subsequent adsorption of a detergent layer on polystyrene. Essential suppression of ionic interactions between soluble low-molecular-mass compounds and the channel wall and decreased adsorption effects were demonstrated in separations of blood samples by gravitational field-flow fractionation.

  6. Trajectory of microscale entities in a microdevice for field-flow fractionation based on dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Mathew, Bobby; Alazzam, Anas; Khashan, Saud A.; El-Khasawneh, Bashar S.

    2015-06-01

    This article deals with the development of a two-dimensional dynamic model for tracking the path of cells subjected to dielectrophoresis, in a continuous flow microfluidic device, for purposes of field-flow fractionation. The nonuniform electric field exists between the top and bottom surface of the microchannel; the top electrode runs over the entire length of the microchannel while the bottom surface of the same holds multiple finite sized electrodes of opposite polarity. The model consists of two governing equations with each describing the movement of the cell in one of the two dimensions of interest. The equations governing of the cell trajectories as well as that of the electric potential inside the microchannel are solved using finite difference method. The model is subsequently used for parametric study; the parameters considered include cell radii, actuation voltage, microchannel height and volumetric flow rate. The model is particularly useful in the design of microfluidic device employing dielectrophoresis for field flow fractionation.

  7. Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

    DOEpatents

    Stevens, Fred J.

    1992-01-01

    A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.

  8. Sedimentation field flow fractionation and flow field flow fractionation as tools for studying the aging effects of WO₃ colloids for photoelectrochemical uses.

    PubMed

    Contado, Catia; Argazzi, Roberto

    2011-07-08

    WO₃ colloidal suspensions obtained through a simple sol-gel procedure were subjected to a controlled temperature aging process whose time evolution in terms of particle mass and size distribution was followed by sedimentation field flow fractionation (SdFFF) and flow field flow fractionation (FlFFF). The experiments performed at a temperature of 60 °C showed that in a few hours the initially transparent sol of WO₃ particles, whose size was less than 25 nm, undergoes a progressive size increase allowing nanoparticles to reach a maximum equivalent spherical size of about 130 nm after 5 h. The observed shift in particle size distribution maxima (SdFFF), the broadening of the curves (FlFFF) and the SEM-TEM observations suggest a mixed mechanism of growth-aggregation of initial nanocrystals to form larger particles. The photoelectrochemical properties of thin WO₃ films obtained from the aged suspensions at regular intervals, were tested in a biased photoelectrocatalytic cell with 1M H₂SO₄ under solar simulated irradiation. The current-voltage polarization curves recorded in the potential range 0-1.8 V (vs. SCE) showed a diminution of the maximum photocurrent from 3.7 mA cm⁻² to 2.8 mA cm⁻² with aging times of 1h and 5h, respectively. This loss of performance was mainly attributed to the reduction of the electroactive surface area of the sintered particles as suggested by the satisfactory linear correlation between the integrated photocurrent and the cyclic voltammetry cathodic wave area of the W(VI)→W(V) process measured in the dark.

  9. [Effects of carrier liquid and flow rate on the separation in gravitational field-flow fractionation].

    PubMed

    Guo, Shuang; Zhu, Chenqi; Gao-Yang, Yaya; Qiu, Bailing; Wu, Di; Liang, Qihui; He, Jiayuan; Han, Nanyin

    2016-02-01

    Gravitational field-flow fractionation is the simplest field-flow fractionation technique in terms of principle and operation. The earth' s gravity is its external field. Different sized particles are injected into a thin channel and carried by carrier fluid. The different velocities of the carrier liquid in different places results in a size-based separation. A gravitational field-flow fractionation (GrFFF) instrument was designed and constructed. Two kinds of polystyrene (PS) particles with different sizes (20 µm and 6 µm) were chosen as model particles. In this work, the separation of the sample was achieved by changing the concentration of NaN3, the percentage of mixed surfactant in the carrier liquid and the flow rate of carrier liquid. Six levels were set for each factor. The effects of these three factors on the retention ratio (R) and plate height (H) of the PS particles were investigated. It was found that R increased and H decreased with increasing particle size. On the other hand, the R and H increased with increasing flow rate. The R and H also increased with increasing NaN3 concentration. The reason was that the electrostatic repulsive force between the particles and the glass channel wall increased. The force allowed the samples approach closer to the channel wall. The results showed that the resolution and retention time can be improved by adjusting the experimental conditions. These results can provide important values to the further applications of GrFFF technique.

  10. Characterization of magnetic nanoparticles using programmed quadrupole magnetic field-flow fractionation

    PubMed Central

    Williams, P. Stephen; Carpino, Francesca; Zborowski, Maciej

    2010-01-01

    Quadrupole magnetic field-flow fractionation is a relatively new technique for the separation and characterization of magnetic nanoparticles. Magnetic nanoparticles are often of composite nature having a magnetic component, which may be a very finely divided material, and a polymeric or other material coating that incorporates this magnetic material and stabilizes the particles in suspension. There may be other components such as antibodies on the surface for specific binding to biological cells, or chemotherapeutic drugs for magnetic drug delivery. Magnetic field-flow fractionation (MgFFF) has the potential for determining the distribution of the magnetic material among the particles in a given sample. MgFFF differs from most other forms of field-flow fractionation in that the magnetic field that brings about particle separation induces magnetic dipole moments in the nanoparticles, and these potentially can interact with one another and perturb the separation. This aspect is examined in the present work. Samples of magnetic nanoparticles were analysed under different experimental conditions to determine the sensitivity of the method to variation of conditions. The results are shown to be consistent and insensitive to conditions, although magnetite content appeared to be somewhat higher than expected. PMID:20732895

  11. Fractionating power and outlet stream polydispersity in asymmetrical flow field-flow fractionation. Part I: isocratic operation.

    PubMed

    Williams, P Stephen

    2016-05-01

    Asymmetrical flow field-flow fractionation (As-FlFFF) has become the most commonly used of the field-flow fractionation techniques. However, because of the interdependence of the channel flow and the cross flow through the accumulation wall, it is the most difficult of the techniques to optimize, particularly for programmed cross flow operation. For the analysis of polydisperse samples, the optimization should ideally be guided by the predicted fractionating power. Many experimentalists, however, neglect fractionating power and rely on light scattering detection simply to confirm apparent selectivity across the breadth of the eluted peak. The size information returned by the light scattering software is assumed to dispense with any reliance on theory to predict retention, and any departure of theoretical predictions from experimental observations is therefore considered of no importance. Separation depends on efficiency as well as selectivity, however, and efficiency can be a strong function of retention. The fractionation of a polydisperse sample by field-flow fractionation never provides a perfectly separated series of monodisperse fractions at the channel outlet. The outlet stream has some residual polydispersity, and it will be shown in this manuscript that the residual polydispersity is inversely related to the fractionating power. Due to the strong dependence of light scattering intensity and its angular distribution on the size of the scattering species, the outlet polydispersity must be minimized if reliable size data are to be obtained from the light scattering detector signal. It is shown that light scattering detection should be used with careful control of fractionating power to obtain optimized analysis of polydisperse samples. Part I is concerned with isocratic operation of As-FlFFF, and part II with programmed operation.

  12. Hollow-Fiber Flow Field-Flow Fractionation for Mass Spectrometry: From Proteins to Whole Bacteria

    NASA Astrophysics Data System (ADS)

    Reschiglian, Pierluigi; Zattoni, Andrea; Rambaldi, Diana Cristina; Roda, Aldo; Hee Moon, Myeong

    Mass spectrometry (MS) provides analyte identification over a wide molar-mass range. However, particularly in the case of complex matrices, this ability is often enhanced by the use of pre-MS separation steps. A separation, prototype technique for the "gentle" fractionation of large/ultralarge analytes, from proteins to whole cells, is here described to reduce complexity and maintain native characteristics of the sample before MS analysis. It is based on flow field-flow fractionation, and it employs a micro-volume fractionation channel made of a ca. 20 cm hollow-fiber membrane of sub-millimeter section. The key advantages of this technique lie in the low volume and low-cost of the channel, which makes it suitable to a disposable usage. Fractionation performance and instrumental simplicity make it an interesting methodology for in-batch or on-line pre-MS treatment of such samples.

  13. Improved performance of gravitational field-flow fractionation for screening wine-making yeast varieties.

    PubMed

    Sanz, R; Torsello, B; Reschiglian, P; Puignou, L; Galceran, M T

    2002-08-09

    Performance of gravitational field-flow fractionation (GFFF) is improved here with respect to the ability to fractionate and distinguish different varieties of wine-making yeast from Saccharomyces cerevisiae. A new GFFF channel with non-polar walls has been employed to enhance fractionation selectivity and reproducibility. Since GFFF retention depends from first principles on particle size, Coulter counter measurements were performed in order to compare size distribution profiles with GFFF profiles. From such a comparison, GFFF was shown to be able to reveal differences in yeast cells other than size. This could make use of GFFF for screening different varieties of wine-making yeast towards future quality assessment procedures based on a possible correlation between yeast cell morphology indexes and quality indexes.

  14. Theory for nanoparticle retention time in the helical channel of quadrupole magnetic field-flow fractionation

    NASA Astrophysics Data System (ADS)

    Williams, P. Stephen; Carpino, Francesca; Zborowski, Maciej

    2009-05-01

    Quadrupole magnetic field-flow fractionation (QMgFFF) is a separation and characterization technique for magnetic nanoparticles such as those used for cell labeling and for targeted drug therapy. A helical separation channel is used to efficiently exploit the quadrupole magnetic field. The fluid and sample components therefore have angular and longitudinal components to their motion in the thin annular space occupied by the helical channel. The retention ratio is defined as the ratio of the times for non-retained and a retained material to pass through the channel. Equations are derived for the respective angular and longitudinal components to retention ratio.

  15. Meeting in Florida: Using Asymmetric Flow Field-Flow Fractionation (AF4) to Determine C60 Colloidal Size Distributions

    EPA Science Inventory

    The study of nanomaterials in environmental systems requires robust and specific analytical methods. Analytical methods which discriminate based on particle size and molecular composition are not widely available. Asymmetric Flow Field-Flow Fractionation (AF4) is a separation...

  16. Meeting in Florida: Using Asymmetric Flow Field-Flow Fractionation (AF4) to Determine C60 Colloidal Size Distributions

    EPA Science Inventory

    The study of nanomaterials in environmental systems requires robust and specific analytical methods. Analytical methods which discriminate based on particle size and molecular composition are not widely available. Asymmetric Flow Field-Flow Fractionation (AF4) is a separation...

  17. Circuit modification in electrical field flow fractionation systems generating higher resolution separation of nanoparticles.

    PubMed

    Tasci, Tonguc O; Johnson, William P; Fernandez, Diego P; Manangon, Eliana; Gale, Bruce K

    2014-10-24

    Compared to other sub-techniques of field flow fractionation (FFF), cyclical electrical field flow fractionation (CyElFFF) is a relatively new method with many opportunities remaining for improvement. One of the most important limitations of this method is the separation of particles smaller than 100nm. For such small particles, the diffusion rate becomes very high, resulting in severe reductions in the CyElFFF separation efficiency. To address this limitation, we modified the electrical circuitry of the ElFFF system. In all earlier ElFFF reports, electrical power sources have been directly connected to the ElFFF channel electrodes, and no alteration has been made in the electrical circuitry of the system. In this work, by using discrete electrical components, such as resistors and diodes, we improved the effective electric field in the system to allow high resolution separations. By modifying the electrical circuitry of the ElFFF system, high resolution separations of 15 and 40nm gold nanoparticles were achieved. The effects of applying different frequencies, amplitudes and voltage shapes have been investigated and analyzed through experiments. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Monitoring the growth of polyoxomolybdate nanoparticles in suspension by flow field-flow fractionation.

    PubMed

    Chen, Bailin; Jiang, Huijian; Zhu, Yan; Cammers, Arthur; Selegue, John P

    2005-03-30

    We follow the evolution of polyoxomolybdate nanoparticles in suspensions derived from the keplerate (NH4)42[MoVI72MoV60O372(CH3CO2)30(H2O)72].ca..300H2O.ca..10CH3CO2NH4 ({Mo132}) by flow field-flow fractionation (FlFFF) to monitor the particle-size distribution in situ, atomic force and high-resolution transmission electron microscopy (AFM, SEM, and HRTEM) to confirm particle sizes, inductively coupled plasma-optical emission spectrometry (ICP-OES) to determine the Mo content of the FlFFF-separated fractions, and UV/visible spectroscopy to confirm the identity of the species in suspension. We observe the formation of 3-75-nm polyoxomolybdate particles in suspension and the dynamic growth of {Mo132} crystals.

  19. Quantitative analysis of virus-like particle size and distribution by field-flow fractionation.

    PubMed

    Chuan, Yap P; Fan, Yuan Y; Lua, Linda; Middelberg, Anton P J

    2008-04-15

    Asymmetric flow field-flow fractionation (AFFFF) coupled with multiple-angle light scattering (MALS) is a powerful technique showing potential for the analysis of pharmaceutically-relevant virus-like particles (VLPs). A lack of published methods, and concerns that membrane adsorption during sample fractionation may cause sample aggregation, have limited widespread acceptance. Here we report a reliable optimized method for VLP analysis using AFFFF-MALS, and benchmark it against dynamic light scattering (DLS) and transmission electron microscopy (TEM). By comparing chemically identical VLPs having very different quaternary structure, sourced from both bacteria and insect cells, we show that optimized AFFFF analysis does not cause significant aggregation, and that accurate size and distribution information can be obtained for heterogeneous samples in a way not possible with TEM and DLS. Optimized AFFFF thus provides a quantitative way to monitor batch consistency for new vaccine products, and rapidly provides unique information on the whole population of particles within a sample.

  20. Combination of gravitational SPLITT fractionation and field-flow fractionation for size-sorting and characterization of sea sediment.

    PubMed

    Moon, Myeong Hee; Yang, Sung Gwon; Lee, Jae Young; Lee, Seungho

    2005-03-01

    A combination of gravitational split-flow thin (SPLITT) fractionation and sedimentation/steric field-flow fractionation (Sd/StFFF) has been used for continuous size-sorting of a sediment sample and for size analysis of the collected fractions. An IAEA (International Atomic Energy Agency) sediment material was separated into four size fractions (with theoretical size ranges <1.0, 1.0-3.0, 3.0-5.0, and >5.0 microm in diameter) by means of a three-step gravitational SPLITT fractionation (GSF) for which the same GSF channel was used throughout. The GSF fractions were collected and examined by optical microscopy (OM) and by Sd/St FFF. The mean diameters of the GSF fractions measured by OM were within the size interval predicted by GSF theory, despite the theory assuming that all particles are spherical, which is not true for the sediment particles. The Sd/St FFF results showed that retention shifted toward shorter elution time (or larger size) than expected, probably because of the shape effect. The results from GSF, OM, and Sd/StFFF are discussed in detail.

  1. High Speed Size Sorting of Subcellular Organelles by Flow Field-Flow Fractionation.

    PubMed

    Yang, Joon Seon; Lee, Ju Yong; Moon, Myeong Hee

    2015-06-16

    Separation/isolation of subcellular species, such as mitochondria, lysosomes, peroxisomes, Golgi apparatus, and others, from cells is important for gaining an understanding of the cellular functions performed by specific organelles. This study introduces a high speed, semipreparative scale, biocompatible size sorting method for the isolation of subcellular organelle species from homogenate mixtures of HEK 293T cells using flow field-flow fractionation (FlFFF). Separation of organelles was achieved using asymmetrical FlFFF (AF4) channel system at the steric/hyperlayer mode in which nuclei, lysosomes, mitochondria, and peroxisomes were separated in a decreasing order of hydrodynamic diameter without complicated preprocessing steps. Fractions in which organelles were not clearly separated were reinjected to AF4 for a finer separation using the normal mode, in which smaller sized species can be well fractionated by an increasing order of diameter. The subcellular species contained in collected AF4 fractions were examined with scanning electron microscopy to evaluate their size and morphology, Western blot analysis using organelle specific markers was used for organelle confirmation, and proteomic analysis was performed with nanoflow liquid chromatography-tandem mass spectrometry (nLC-ESI-MS/MS). Since FlFFF operates with biocompatible buffer solutions, it offers great flexibility in handling subcellular components without relying on a high concentration sucrose solution for centrifugation or affinity- or fluorescence tag-based sorting methods. Consequently, the current study provides an alternative, competitive method for the isolation/purification of subcellular organelle species in their intact states.

  2. Development of a downscale sedimentation field flow fractionation device for biological event monitoring.

    PubMed

    Bégaud-Grimaud, G; Battu, S; Liagre, B; Beneytout, J L; Jauberteau, M O; Cardot, P J P

    2009-12-25

    Classically described as a macroscale size-density based method, Sedimentation field flow fractionation (SdFFF) has been successfully used for cell sorting. The goal of this study was to develop a new SdFFF device for downscale applications, in particular for oncology research to rapidly monitor chemical biological event induction in a cell line. The development of a downscale SdFFF device required reduction of the separation channel volume. Taking advantage of a newly laboratory designed apparatus, channel volume was successfully decreased by reducing both length and breadth. To validate the apparatus and method, we used the well-known model of diosgenin dose-dependent induction of apoptosis or megakaryocytic differentiation in HEL cells. After a minute scale acquisition of a reference profile, the downscale device was able to perform fast, early, significant and reproducible monitoring of apoptosis and differentiation, two important biological mechanisms in the field of cancer research.

  3. Size characterization of inclusion bodies by sedimentation field-flow fractionation

    PubMed Central

    Margreiter, Gerd; Messner, Paul; Caldwell, Karin D.; Bayer, Karl

    2015-01-01

    Sedimentation field-flow fractionation (sedFFF) was evaluated to characterize the size of Δ(4–23)TEM-β-lactamase inclusion bodies (IBs) overexpressed in fed-batch cultivations of Escherichia coli. Heterologous Δ(4–23)TEM-β-lactamase protein formed different sizes of IBs, depending upon the induction conditions. In the early phases of recombinant protein expression, induced with low concentrations of IPTG (isopropyl-β-d-thiogalactoside), IB masses were larger than expected and showed heterogeneous size distributions. During cultivation, IB sizes showed a Gaussian distribution and reached a broad range by the end of the fed-batch cultivations. The obtained result proved the aptitude of sedFFF to rapidly assess the size distribution of IBs in a culture. PMID:18760314

  4. Development of flow/steric field-flow fractionation as a routine process control method

    SciTech Connect

    Barman, B.N.

    1988-08-30

    Researchers studied the feasibility of using the Flow/Steric Field-Flow Fractionation (Flow/StFFF) method for the characterization of particulate materials with diameters in the 1-100 micrometers range. Studies on the optimization of the method for the separation and characterization of different size particulate samples, as well as on the role of the crossflow field and channel flowrate on the separation and resolution, were performed with a number of spherical polystyrene divinylbenzene latex standards and included in the report. Applicability of the method as a fast and reliable practical tool for industrial process control, particularly for grinding operations, was examined by analyzing a number of samples obtained by grinding. Examples of materials considered include coal, limestone and glass.

  5. Hydrodynamic chromatography and field flow fractionation in finite aspect ratio channels.

    PubMed

    Shendruk, T N; Slater, G W

    2014-04-25

    Hydrodynamic chromatography (HC) and field-flow fractionation (FFF) separation methods are often performed in 3D rectangular channels, though ideal retention theory assumes 2D systems. Devices are commonly designed with large aspect ratios; however, it can be unavoidable or desirable to design rectangular channels with small or even near-unity aspect ratios. To assess the significance of finite-aspect ratio effects and interpret experimental retention results, an ideal, analytical retention theory is needed. We derive a series solution for the ideal retention ratio of HC and FFF rectangular channels. Rather than limiting devices' ability to resolve samples, our theory predicts that retention curves for normal-mode FFF are well approximated by the infinite plate solution and that the performance of HC is actually improved. These findings suggest that FFF devices need not be designed with large aspect ratios and that rectangular HC channels are optimal when the aspect ratio is unity.

  6. Nanoparticle separation with a miniaturized asymmetrical flow field-flow fractionation cartridge

    PubMed Central

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; de Mello, Andrew J.

    2015-01-01

    Asymmetrical Flow Field-Flow Fractionation (AF4) is a separation technique applicable to particles over a wide size range. Despite the many advantages of AF4, its adoption in routine particle analysis is somewhat limited by the large footprint of currently available separation cartridges, extended analysis times and significant solvent consumption. To address these issues, we describe the fabrication and characterization of miniaturized AF4 cartridges. Key features of the down-scaled platform include simplified cartridge and reagent handling, reduced analysis costs and higher throughput capacities. The separation performance of the miniaturized cartridge is assessed using certified gold and silver nanoparticle standards. Analysis of gold nanoparticle populations indicates shorter analysis times and increased sensitivity compared to conventional AF4 separation schemes. Moreover, nanoparticulate titanium dioxide populations exhibiting broad size distributions are analyzed in a rapid and efficient manner. Finally, the repeatability and reproducibility of the miniaturized platform are investigated with respect to analysis time and separation efficiency. PMID:26258119

  7. A novel approach to improve operation and performance in flow field-flow fractionation.

    PubMed

    Johann, Christoph; Elsenberg, Stephan; Roesch, Ulrich; Rambaldi, Diana C; Zattoni, Andrea; Reschiglian, Pierluigi

    2011-07-08

    A new system design and setup are proposed for the combined use of asymmetrical flow field-flow fractionation (AF4) and hollow-fiber flow field-flow fractionation (HF5) within the same instrumentation. To this purpose, three innovations are presented: (a) a new flow control scheme where focusing flow rates are measured in real time allowing to adjust the flow rate ratio as desired; (b) a new HF5 channel design consisting of two sets of ferrule, gasket and cap nut used to mount the fiber inside a tube. This design provides a mechanism for effective and straightforward sealing of the fiber; (c) a new AF4 channel design with only two fluid connections on the upper plate. Only one pump is needed to deliver the necessary flow rates. In the focusing/relaxation step the two parts of the focusing flow and a bypass flow flushing the detectors are created with two splits of the flow from the pump. In the elution mode the cross-flow is measured and controlled with a flow controller device. This leads to reduced pressure pulsations in the channel and improves signal to noise ratio in the detectors. Experimental results of the separation of bovine serum albumin (BSA) and of a mix of four proteins demonstrate a significant improvement in the HF5 separation performance, in terms of efficiency, resolution, and run-to-run reproducibility compared to what has been reported in the literature. Separation performance in HF5 mode is shown to be comparable to the performance in AF4 mode using a channel with two connections in the upper plate.

  8. Size characterization of incinerator fly ash using sedimentation/steric field-flow fractionation.

    PubMed

    Kimt, Won-Suk; Lee, Dai Woon; Lee, Seungho

    2002-02-15

    Fly ash particles emitted from municipal solid waste-incinerators are of environmental concern. This study aims to investigate the applicability of sedimentation/steric field-flow fractionation (Sd/StFFF) and to develop a Sd/StFFF method for the separation and size characterization of incinerator fly ash. This study focuses on the fly ash particles larger than approxiamtely 1 microm, which comprise more than 90% (w/w) of the fly ash. Fly ash is a complex mixture of particles having various chemical compositions, sizes, shapes, and densities. Prior to Sd/StFFF analysis, fly ash particles are prefractionated into six density classes using a modified centrifugal procedure. It was found that fly ash particles are most abundant in the density range between 2.4 and 2.8 g/cm3. Different density fractions seem to contain particles of different chemical compositions. The Sd/StFFF conditions for the size-characterization of fly ash are sample concentration, approximately 0.3% (w/v); dispersing medium, 50% ethanol in water; and carrier liquid, water with 1.0% FL-70 (ionic strength approximately 0.012 M). Sd/StFFF data show no significant differences in size distribution among different density fractions. Generally, the sizes obtained from Sd/StFFF are larger than those obtained from a Coulter Multisizer and microscopy, probably because of the irregular shapes of the fly ash particles.

  9. Asymmetric flow field-flow fractionation of manufactured silver nanoparticles spiked into soil solution.

    PubMed

    Koopmans, G F; Hiemstra, T; Regelink, I C; Molleman, B; Comans, R N J

    2015-05-01

    Manufactured metallic silver nanoparticles (AgNP) are intensively utilized in consumer products and this will inevitably lead to their release to soils. To assess the environmental risks of AgNP in soils, quantification of both their concentration and size in soil solution is essential. We developed a methodology consisting of asymmetric flow field-flow fractionation (AF4) in combination with on-line detection by UV-vis spectroscopy and off-line HR-ICP-MS measurements to quantify the concentration and size of AgNP, coated with either citrate or polyvinylpyrrolidone (PVP), in water extracts of three different soils. The type of mobile phase was a critical factor in the fractionation of AgNP by AF4. In synthetic systems, fractionation of a series of virgin citrate- and PVP-coated AgNP (10-90 nm) with reasonably high recoveries could only be achieved with ultrahigh purity water as a mobile phase. For the soil water extracts, 0.01% (w:v) sodium dodecyl sulfate (SDS) at pH 8 was the key to a successful fractionation of the AgNP. With SDS, the primary size of AgNP in all soil water extracts could be determined by AF4, except for PVP-coated AgNP when clay colloids were present. The PVP-coated AgNP interacted with colloidal clay minerals, leading to an overestimation of their primary size. Similar interactions between PVP-coated AgNP and clay colloids can take place in the environment and facilitate their transport in soils, aquifers, and surface waters. In conclusion, AF4 in combination with UV-vis spectroscopy and HR-ICP-MS measurements is a powerful tool to characterize AgNP in soil solution if the appropriate mobile phase is used. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Size characterization by Sedimentation Field Flow Fractionation of silica particles used as food additives.

    PubMed

    Contado, Catia; Ravani, Laura; Passarella, Martina

    2013-07-25

    Four types of SiO2, available on the market as additives in food and personal care products, were size characterized using Sedimentation Field Flow Fractionation (SdFFF), SEM, TEM and Photon Correlation Spectroscopy (PCS). The synergic use of the different analytical techniques made it possible, for some samples, to confirm the presence of primary nanoparticles (10 nm) organized in clusters or aggregates of different dimension and, for others, to discover that the available information is incomplete, particularly that regarding the presence of small particles. A protocol to extract the silica particles from a simple food matrix was set up, enriching (0.25%, w w(-1)) a nearly silica-free instant barley coffee powder with a known SiO2 sample. The SdFFF technique, in conjunction with SEM observations, made it possible to identify the added SiO2 particles and verify the new particle size distribution. The SiO2 content of different powdered foodstuffs was determined by graphite furnace atomic absorption spectroscopy (GFAAS); the concentrations ranged between 0.006 and 0.35% (w w(-1)). The protocol to isolate the silica particles was so applied to the most SiO2-rich commercial products and the derived suspensions were separated by SdFFF; SEM and TEM observations supported the size analyses while GFAAS determinations on collected fractions permitted element identification. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Hybrid gravitational field-flow fractionation using immunofunctionalized walls for integrated bioanalytical devices.

    PubMed

    Roda, Barbara; Casolari, Sonia; Reschiglian, Pierluigi; Mirasoli, Mara; Simoni, Patrizia; Roda, Aldo

    2009-06-01

    In this work, the biospecific recognition antigen-antibody reaction was implemented in gravitational field-flow fractionation (GrFFF), a flow-assisted separation technique for micron-sized particles, in order to realize a hybrid immunomodulated GrFFF system in which two different principles are combined to achieve highly versatile fractionation. Micron-sized polystyrene beads coated with horseradish peroxidase (HRP) were used as a model sample, and anti-HRP antibodies were immobilized on the accumulation wall of the GrFFF channel. Ultrasensitive chemiluminescence imaging was employed to visualize the beads during elution and to optimize experimental conditions. The same principle was then applied to real biological samples composed by Yersinia enterocolitica and Escherichia coli cells. Results show the possibility to modify the elution of selected sample components and even to retain them into the channel. The hybrid immunomodulated GrFFF system is a step towards the development of a module that could be integrated in a lab-on-a-chip-based point-of-care testing device which includes sample pre-analytical cleanup and analysis.

  12. Analysis of plant ribosomes with asymmetric flow field-flow fractionation.

    PubMed

    Pitkänen, Leena; Tuomainen, Päivi; Eskelin, Katri

    2014-02-01

    Ribosome profiling is a technique used to separate ribosomal subunits, 80S ribosomes (monosomes), and polyribosomes (polysomes) from other RNA-protein complexes. It is traditionally performed in sucrose gradients. In this study, we used asymmetric flow field-flow fractionation (AsFlFFF) to characterize ribosome profiles of Nicotiana benthamiana plants. With the optimized running conditions, we were able to separate free molecules from ribosomal subunits and intact ribosomes. We used various chemical and enzymatic treatments to validate the positions of subunits, monosomes, and polysomes in the AsFlFFF fractograms. We also characterized the protein and RNA content of AsFlFFF fractions by gel electrophoresis and western blotting. The reverse transcription polymerase chain reaction (RT-PCR) analysis showed that ribosomes remained bound to messenger RNAs (mRNAs) during the analysis. Therefore, we conclude that AsFlFFF can be used for ribosome profiling to study the mRNAs that are being translated. It can also be used to study the protein composition of ribosomes that are active in translation at that particular moment.

  13. Fractionating power and outlet stream polydispersity in asymmetrical flow field-flow fractionation. Part II: programmed operation.

    PubMed

    Williams, P Stephen

    2017-01-01

    Asymmetrical flow field-flow fractionation (As-FlFFF) is a widely used technique for analyzing polydisperse nanoparticle and macromolecular samples. The programmed decay of cross flow rate is often employed. The interdependence of the cross flow rate through the membrane and the fluid flow along the channel length complicates the prediction of elution time and fractionating power. The theory for their calculation is presented. It is also confirmed for examples of exponential decay of cross flow rate with constant channel outlet flow rate that the residual sample polydispersity at the channel outlet is quite well approximated by the reciprocal of four times the fractionating power. Residual polydispersity is of importance when online MALS or DLS detection are used to extract quantitative information on particle size or molecular weight. The theory presented here provides a firm basis for the optimization of programmed flow conditions in As-FlFFF. Graphical abstract Channel outlet polydispersity remains significant following fractionation by As-FlFFF under conditions of programmed decay of cross flow rate.

  14. Optimization and evaluation of asymmetric flow field-flow fractionation of silver nanoparticles.

    PubMed

    Loeschner, Katrin; Navratilova, Jana; Legros, Samuel; Wagner, Stephan; Grombe, Ringo; Snell, James; von der Kammer, Frank; Larsen, Erik H

    2013-01-11

    Asymmetric flow field-flow fractionation (AF(4)) in combination with on-line optical detection and mass spectrometry is one of the most promising methods for separation and quantification of nanoparticles (NPs) in complex matrices including food. However, to obtain meaningful results regarding especially the NP size distribution a number of parameters influencing the separation need to be optimized. This paper describes the development of a separation method for polyvinylpyrrolidone-stabilized silver nanoparticles (AgNPs) in aqueous suspension. Carrier liquid composition, membrane material, cross flow rate and spacer height were shown to have a significant influence on the recoveries and retention times of the nanoparticles. Focus time and focus flow rate were optimized with regard to minimum elution of AgNPs in the void volume. The developed method was successfully tested for injected masses of AgNPs from 0.2 to 5.0 μg. The on-line combination of AF(4) with detection methods including ICP-MS, light absorbance and light scattering was helpful because each detector provided different types of information about the eluting NP fraction. Differences in the time-resolved appearance of the signals obtained by the three detection methods were explained based on the physical origin of the signal. Two different approaches for conversion of retention times of AgNPs to their corresponding sizes and size distributions were tested and compared, namely size calibration with polystyrene nanoparticles (PSNPs) and calculations of size based on AF(4) theory. Fraction collection followed by transmission electron microscopy was performed to confirm the obtained size distributions and to obtain further information regarding the AgNP shape. Characteristics of the absorbance spectra were used to confirm the presence of non-spherical AgNP.

  15. Magnetic Nanoparticle Drug Carriers and their Study by Quadrupole Magnetic Field-Flow Fractionation

    PubMed Central

    Williams, P. Stephen; Carpino, Francesca; Zborowski, Maciej

    2009-01-01

    Magnetic nanoparticle drug carriers continue to attract considerable interest for drug targeting in the treatment of cancers and other pathological conditions. The efficient delivery of therapeutic levels of drug to a target site while limiting nonspecific, systemic toxicity requires optimization of the drug delivery materials, the applied magnetic field, and the treatment protocol. The history and current state of magnetic drug targeting is reviewed. While initial studies involved micron-sized and larger carriers, and work with these microcarriers continues, it is the sub-micron carriers or nanocarriers that are of increasing interest. An aspect of magnetic drug targeting using nanoparticle carriers that has not been considered is then addressed. This aspect involves the variation in the magnetic properties of the nanocarriers. Quadrupole magnetic field-flow fractionation (QMgFFF) is a relatively new technique for characterizing magnetic nanoparticles. It is unique in its capability of determining the distribution in magnetic properties of a nanoparticle sample in suspension. The development and current state of this technique is also reviewed. Magnetic nanoparticle drug carriers have been found by QMgFFF analysis to be highly polydisperse in their magnetic properties, and the strength of response of the particles to magnetic field gradients is predicted to vary by orders of magnitude. It is expected that the least magnetic fraction of a formulation will contribute the most to systemic toxicity, and the depletion of this fraction will result in a more effective drug carrying material. A material that has a reduced systemic toxicity will allow higher doses of cytotoxic drugs to be delivered to the tumor with reduced side effects. Preliminary experiments involving a novel method of refining a magnetic nanoparticle drug carrier to achieve this result are described. QMgFFF is used to characterize the refined and unrefined material. PMID:19591456

  16. Asymmetric flow field flow fractionation with light scattering detection - an orthogonal sensitivity analysis.

    PubMed

    Galyean, Anne A; Filliben, James J; Holbrook, R David; Vreeland, Wyatt N; Weinberg, Howard S

    2016-11-18

    Asymmetric flow field flow fractionation (AF(4)) has several instrumental factors that may have a direct effect on separation performance. A sensitivity analysis was applied to ascertain the relative importance of AF(4) primary instrument factor settings for the separation of a complex environmental sample. The analysis evaluated the impact of instrumental factors namely, cross flow, ramp time, focus flow, injection volume, and run buffer concentration on the multi-angle light scattering measurement of natural organic matter (NOM) molar mass (MM). A 2((5-1)) orthogonal fractional factorial design was used to minimize analysis time while preserving the accuracy and robustness in the determination of the main effects and interactions between any two instrumental factors. By assuming that separations resulting in smaller MM measurements would be more accurate, the analysis produced a ranked list of effects estimates for factors and interactions of factors based on their relative importance in minimizing the MM. The most important and statistically significant AF(4) instrumental factors were buffer concentration and cross flow. The least important was ramp time. A parallel 2((5-2)) orthogonal fractional factorial design was also employed on five environmental factors for synthetic natural water samples containing silver nanoparticles (NPs), namely: NP concentration, NP size, NOM concentration, specific conductance, and pH. None of the water quality characteristic effects or interactions were found to be significant in minimizing the measured MM; however, the interaction between NP concentration and NP size was an important effect when considering NOM recovery. This work presents a structured approach for the rigorous assessment of AF(4) instrument factors and optimal settings for the separation of complex samples utilizing efficient orthogonal factional factorial design and appropriate graphical analysis.

  17. Flow field-flow fractionation and multiangle light scattering for ultrahigh molecular weight sodium hyaluronate characterization.

    PubMed

    Moon, Myeong Hee

    2010-11-01

    This review describes the utility of flow field-flow fractionation coupled with multiangle light scattering and differential refractive index (FlFFF-MALS-DRI) detection methods for the separation of ultrahigh molecular weight sodium hyaluronate (NaHA) materials and for the characterization of molecular weight distribution as well as structural determination. The sodium salt of hyaluronic acid (HA), NaHA, is a water-soluble polysaccharide with a broad range of molecular weights (10(5) -10(8) ) found in various naturally occurring fluids and tissues. Basic principles of FlFFF-MALS using field programming for the separation of the degraded products of NaHA prepared by treating raw materials with depolymerization or degradation processes such as membrane filtration, enzymatic degradation, ultrasonic degradation, alkaline reaction, irradiation by γ-rays, and thermal treatment for the development of pharmaceutical applications are introduced. Changes in molecular weight distribution and conformation of NaHA materials due to external stimuli are also discussed. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Asymmetrical flow field-flow fractionation for the analysis of PEG-asparaginase.

    PubMed

    John, C; Herz, T; Boos, J; Langer, K; Hempel, G

    2016-01-01

    Monomethoxypolyethylene glycol L-asparaginase (PEG-ASNASE) is the PEGylated version of the enzyme L-asparaginase (ASNASE). Both are used for remission induction in acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL). The treatment control is generally carried out by performing activity assays, though methods to determine the actual enzyme rather than its activity are rare. Using asymmetrical flow field-flow fractionation (AF4) offered the chance to develop a method capable of simultaneously measuring PEG-ASNASE and PEG. A method validation was performed in accordance with FDA guidelines for PEG-ASNASE from non-biological solutions. The method unfolded a linearity of 15-750 U/mL with coefficients of correlation of r(2)>0.99. The coefficients of variation (CV) for within-run and between-run variability were 1.18-10.15% and 2.43-8.73%, respectively. Furthermore, the method was used to perform stability tests of the product Oncaspar® (PEG-ASNASE) and estimation of the molecular weight by multi-angle light scattering (MALS) of stressed samples to correlate them with the corresponding activity. The findings indicate that Oncaspar® stock solution should not be stored any longer than 24 h at room temperature and cannot be frozen in pure aqueous media. The validated method might be useful for the pharmaceutical industry and its quality control of PEG-ASNASE production.

  19. Zeta-potential Analyses using Micro Electrical Field Flow Fractionation with Fluorescent Nanoparticles

    PubMed Central

    Chang, Moon-Hwan; Dosev, Dosi; Kennedy, Ian M.

    2007-01-01

    Increasingly growing application of nanoparticles in biotechnology requires fast and accessible tools for their manipulation and for characterization of their colloidal properties. In this work we determine the zeta-potentials for polystyrene nanoparticles using micro electrical field flow fractionation (μ–EFFF) which is an efficient method for sorting of particles by size. The data obtained by μ–EFFF were compared to zeta potentials determined by standard capillary electrophoresis. For proof of concept, we used polystyrene nanoparticles of two different sizes, impregnated with two different fluorescent dyes. Fluorescent emission spectra were used to evaluate the particle separation in both systems. Using the theory of electrophoresis, we estimated the zeta-potentials as a function of size, dielectric permittivity, viscosity and electrophoretic mobility. The results obtained by the μ–EFFF technique were confirmed by the conventional capillary electrophoresis measurements. These results demonstrate the applicability of the μ–EFFF method not only for particle size separation but also as a simple and inexpensive tool for measurements of nanoparticles zeta potentials. PMID:18542710

  20. Use of fluorescent probes for determination of yeast cell viability by gravitational field-flow fractionation.

    PubMed

    Garcia, M T; Sanz, R; Galceran, M T; Puignou, L

    2006-01-01

    The quality of wine greatly depends on the features of the yeast used in its production, and yeast cell viability is one of the most important quality control issues to consider in this regard. In the first steps of winemaking, the use of a low-cost and simple methodology for monitoring the cell viability of yeast inoculates is of paramount importance. Gravitational field-flow fractionation is a useful technique for the determination of cell viability because it provides gentle experimental conditions, although the proper use of fluorophore probes as biomass indicators is required. In this paper the use of different fluorescent probes such as carboxyfluorescein diacetate (cFDA), calcein-AM, and SYTO-13 were considered as viability biomarkers. Calceina-AM allowed the establishment of a direct GrFFF method to determine cell viability, with a limit of detection of 5.0 x 10(4) viable cell/mL. SYTO-13 could be used as biomass indicator with a limit of detection of 3.5 x 10(4) total cells/mL. The suitability of the procedure was tested with three commercial yeast samples, and the results were compared with those obtained using standard techniques.

  1. Monitoring of barley starch amylolysis by gravitational field flow fractionation and MALDI-TOF MS.

    PubMed

    Mazanec, Karel; Dycka, Filip; Bobalova, Janette

    2011-12-01

    In barley, starch occurs in the form of granules with bimodal size distribution. Enzymatic hydrolysis of the starch granule is one of the most important reactions occurring during malting and mashing. Previous studies revealed the discrepancies in the assumption that barley varieties with better malting qualities should have a higher A/B (large/small starch granules) ratio. This led us to focus our attention on detailed analysis of two barley varieties, Jersey and Tolar, both with high malting quality but significantly differing in A/B (1.28 and 0.66, respectively), were chosen for more detailed analysis in the actual work. In this study, the capacity of gravitational field flow fractionation (GFFF) to monitor amylolysis of the starch granules was investigated. Isolated starch granules from these two barley cultivars were treated with amylases. The changes in starch granule size and bimodal distribution were studied by GFFF. Simultaneously, free sugars released during enzymatic digestion were observed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The changes in the fractogram and in the mass spectra reflect a correlation with the progress of enzymatic hydrolysis. The results show the interest in utilization of GFFF as a simple and cheap method for monitoring changes in the distribution of the starch granule size during amylolysis. Copyright © 2011 Society of Chemical Industry.

  2. Macromolecular geometries determined with field-flow fractionation and their impact on the overlap concentration.

    PubMed

    Rojas, Cinthia Carola; Wahlund, Karl-Gustav; Bergenståhl, Björn; Nilsson, Lars

    2008-06-01

    In this paper we aim to understand the size/conformation relationship in waxy barley starch, a polydisperse and ultrahigh molar mass biomacromolecule. Characterizations are performed with asymmetrical flow field-flow fractionation (AsFlFFF). Furthermore, we study the effect of homogenization on the molar mass, rms radius (r rms) and hydrodynamic radius (r h). For the untreated sample, the macromolecules are elongated objects with low apparent density. As a result of homogenization, molar mass, and r rms decrease, while r h remains unaffected. The process also induces an increase, and scaling with size, of apparent density as well as changes in conformation, represented qualitatively by r rms/ r h. Finally, results from AsFlFFF are compared with viscosimetry and discussed in terms of concentration and close-packing in relation to macromolecular shape and conformation. Hence, the results show that AsFlFFF and our novel methodology enable the determination of several physical properties with high relevance for the solution behavior of polydisperse macromolecules.

  3. Biased cyclical electrical field-flow fractionation for separation of submicron particles.

    PubMed

    Ornthai, Mathuros; Siripinyanond, Atitaya; Gale, Bruce K

    2016-01-01

    The potential of biased cyclical electrical field-flow fractionation (BCyElFFF), which applies the positive cycle voltage longer than the negative cycle voltage, for characterization of submicron particles, was investigated. Parameters affecting separation and retention such as voltage, frequency, and duty cycle were examined. The results suggest that the separation mechanism in BCyElFFF in many cases is more related to the size of particles, as is the case with normal ElFFF, in the studied conditions, than the electrophoretic mobility, which is what the theory predicts for CyElFFF. However, better resolution was obtained when separating using BCyElFFF mode than when using normal CyElFFF. BCyElFFF was able to demonstrate simultaneous baseline separations of a mixture of 0.04-, 0.1-, and 0.2-μm particles and near separation of 0.5-μm particles. This study has shown the applicability of BCyElFFF for separation and characterization of submicron particles greater than 0.1-μm in size, which had not been demonstrated previously. The separation and retention results suggest that for particles of this size, retention is based more on particle size than on electrophoretic mobility, which is contrary to existing theory for CyElFFF.

  4. Size sorting of citrate reduced gold nanoparticles by sedimentation field-flow fractionation.

    PubMed

    Contado, Catia; Argazzi, Roberto

    2009-12-25

    Gold nanoparticles (GNPs) have been synthesized through the citrate reduction method; the citrate/gold(III) ratio was changed from 1:1 up to 10:1 and the size of the resulting nanoparticles was measured by sedimentation field-flow fractionation (SdFFF). Experimental data showed that the GNPs size decreases in the ratio range 1:1-3:1 and then increases from 5:1 to 10:1 passing through a plateau region in between, and is almost independent of the precursor solution concentrations. In the zone of minimum diameters the synthetic process does not produce monodispersed GNPs but often multiple distributions, very close in size, are observed as evidenced by the particle size distributions (PSDs) derived from the SdFFF fractograms. UV-vis spectrophotometry, being the most common technique employed in the optical characterization of nanoparticles suspensions, was used throughout this work. A confirmation of the nucleation-aggregation-fragmentation mechanism was inferred from the cross-correlation between UV-vis and SdFFF results.

  5. Sedimentation field flow fractionation and optical absorption spectroscopy for a quantitative size characterization of silver nanoparticles.

    PubMed

    Contado, Catia; Argazzi, Roberto; Amendola, Vincenzo

    2016-11-04

    Many advanced industrial and biomedical applications that use silver nanoparticles (AgNPs), require that particles are not only nano-sized, but also well dispersed, not aggregated and not agglomerated. This study presents two methods able to give rapidly sizes of monodispersed AgNPs suspensions in the dimensional range of 20-100nm. The first method, based on the application of Mie's theory, determines the particle sizes from the values of the surface plasmon resonance wavelength (SPRMAX), read from the optical absorption spectra, recorded between 190nm and 800nm. The computed sizes were compared with those determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) and resulted in agreement with the nominal values in a range between 13% (for 20nm NPs) and 1% (for 100nm NPs), The second method is based on the masterly combination of the Sedimentation Field Flow Fractionation (SdFFF - now sold as Centrifugal FFF-CFFF) and the Optical Absorption Spectroscopy (OAS) techniques to accomplish sizes and quantitative particle size distributions for monodispersed, non-aggregated AgNPs suspensions. The SdFFF separation abilities, well exploited to size NPs, greatly benefits from the application of Mie's theory to the UV-vis signal elaboration, producing quantitative mass-based particle size distributions, from which trusted number-sized particle size distributions can be derived. The silver mass distributions were verified and supported by detecting off-line the Ag concentration with the graphite furnace atomic absorption spectrometry (GF-AAS).

  6. Comparison of on-line detectors for field flow fractionation analysis of nanomaterials.

    PubMed

    Bednar, A J; Poda, A R; Mitrano, D M; Kennedy, A J; Gray, E P; Ranville, J F; Hayes, C A; Crocker, F H; Steevens, J A

    2013-01-30

    Characterization of nanomaterials must include analysis of both size and chemical composition. Many analytical techniques, such as dynamic light scattering (DLS), are capable of measuring the size of suspended nanometer-sized particles, yet provide no information on the composition of the particle. While field flow fractionation (FFF) is a powerful nanoparticle sizing technique, common detectors used in conjunction with the size separation, including UV, light-scattering, and fluorescence spectroscopy, do not provide the needed particle compositional information. Further, these detectors do not respond directly to the mass concentration of nanoparticles. The present work describes the advantages achieved when interfacing sensitive and elemental specific detectors, such as inductively coupled plasma atomic emission spectroscopy and mass spectrometry, to FFF separation analysis to provide high resolution nanoparticle sizing and compositional analysis at the μg/L concentration level, a detection at least 10-100-fold lower than DLS or FFF-UV techniques. The full benefits are only achieved by utilization of all detector capabilities, such as dynamic reaction cell (DRC) ICP-MS. Such low-level detection and characterization capability is critical to nanomaterial investigations at biologically and environmentally relevant concentrations. The techniques have been modified and applied to characterization of all four elemental constituents of cadmium selenide-zinc sulfide core-shell quantum dots, and silver nanoparticles with gold seed cores. Additionally, sulfide coatings on silver nanoparticles can be detected as a potential means to determine environmental aging of nanoparticles.

  7. Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study.

    PubMed

    Baken, Stijn; Regelink, Inge C; Comans, Rob N J; Smolders, Erik; Koopmans, Gerwin F

    2016-08-01

    Colloidal phosphorus (P) may represent an important fraction of the P in natural waters, but these colloids remain poorly characterized. In this work, we demonstrate the applicability of asymmetric flow field-flow fractionation (AF4) coupled to high resolution ICP-MS for the characterization of low concentrations of P-bearing colloids. Colloids from five streams draining catchments with contrasting properties were characterized by AF4-ICP-MS and by membrane filtration. All streams contain free humic substances (2-3 nm) and Fe-bearing colloids (3-1200 nm). Two soft water streams contain primary Fe oxyhydroxide-humic nanoparticles (3-6 nm) and aggregates thereof (up to 150 nm). In contrast, three harder water streams contain larger aggregates (40-1200 nm) which consist of diverse associations between Fe oxyhydroxides, humic substances, clay minerals, and possibly ferric phosphate minerals. Despite the diversity of colloids encountered in these contrasting streams, P is in most of the samples predominantly associated with Fe-bearing colloids (mostly Fe oxyhydroxides) at molar P:Fe ratios between 0.02 and 1.5. The molar P:Fe ratio of the waters explains the partitioning of P between colloids and truly dissolved species. Waters with a high P:Fe ratio predominantly contain truly dissolved species because the Fe-rich colloids are saturated with P, whereas waters with a low P:Fe ratio mostly contain colloidal P species. Overall, AF4-ICP-MS is a suitable technique to characterize the diverse P-binding colloids in natural waters. Such colloids may increase the mobility or decrease the bioavailability of P, and they therefore need to be considered when addressing the transport and environmental effects of P in catchments. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Particle characterization in centrifugal fields. Comparison between ultracentrifugation and sedimentation field-flow fractionation.

    PubMed

    Li, J M; Caldwell, K D; Mächtle, W

    1990-09-26

    A ten-component mixture of polystyrene latex particles in the 67-1220 nm size range was subjected to analysis by analytical ultracentrifugation (AUC) and sedimentation field-flow fractionation (SdFFF) using programmed and constant fields. The AUC analysis of the mixture yielded diameter values in good agreement with data determined on the separate components; the relative amounts of each component in the mixture were likewise closely reproducing the sample's known composition. Diameters determined by SdFFF, either in a constant- or programmed-field mode, were in good agreement with the AUC for particles smaller than about 500 nm. For the sample's larger components, however, particularly the programmed mode showed diameter values smaller than expected. In addition, field programming resulted in incomplete recoveries of the larger particles, leading to more or less distorted mass distributions for the complex sample. The observed discrepancies, which are thought to result from events at the analytical wall in the FFF channel, suggested a protocol for accurate sizing, as opposed to fingerprinting, of samples with broad size distribution. By tracking sizes and amounts of the different components at different but constant field strengths, and retaining as analytically valid only those data recorded in a retention range from five to about thirty column volumes, it was possible to determine sizes and amounts in good agreement with known parameters for the sample. Unlike the AUC procedure, SdFFF produces fractions of a high degree of uniformity, which lend themselves to a secondary analysis, e.g. by electron microscopy, as shown in the study.

  9. Frit inlet field-flow fractionation techniques for the characterization of polyion complex self-assemblies.

    PubMed

    Till, Ugo; Gaucher, Mireille; Amouroux, Baptiste; Gineste, Stéphane; Lonetti, Barbara; Marty, Jean-Daniel; Mingotaud, Christophe; Bria, Carmen R M; Williams, S Kim Ratanathanawongs; Violleau, Frédéric; Mingotaud, Anne-Françoise

    2017-01-20

    Polymer self-assemblies joining oppositely charged chains, known as polyion complexes (PICs), have been formed using poly(ethyleneoxide - b - acrylic acid)/poly(l-lysine), poly(ethyleneoxide-b-acrylic acid)/dendrigraft poly(l-lysine) and poly[(3-acrylamidopropyl) trimethylammonium chloride - b - N - isopropyl acrylamide]/poly(acrylic acid). The self-assemblies have been first characterized in batch by Dynamic Light Scattering. In a second step, their analysis by Flow Field-Flow Fractionation techniques (FlFFF) was examined. They were shown to be very sensitive to shearing, especially during the focus step of the fractionation, and this led to an incompatibility with asymmetrical FlFFF. On the other hand, Frit Inlet FlFFF proved to be very efficient to observe them, either in its symmetrical (FI-FlFFF) or asymmetrical version (FI-AsFlFFF). Conditions of elution were found to optimize the sample recovery in pure water. Spherical self-assemblies were detected, with a size range between 70-400nm depending on the polymers. Compared to batch DLS, FI-AsFlFFF clearly showed the presence of several populations in some cases. The influence of salt on poly(ethyleneoxide-b-acrylic acid) (PEO-PAA) 6000-3000/dendrigraft poly(l-lysine) (DGL 3) was also assessed in parallel in batch DLS and FI-AsFlFFF. Batch DLS revealed a first process of swelling of the self-assembly for low concentrations up to 0.8M followed by the dissociation. FI-AsFlFFF furthermore indicated a possible ejection of DGL3 from the PIC assembly for concentrations as low as 0.2M, which could not be observed in batch DLS.

  10. Probing and quantifying DNA-protein interactions with asymmetrical flow field-flow fractionation.

    PubMed

    Ashby, Jonathan; Schachermeyer, Samantha; Duan, Yaokai; Jimenez, Luis A; Zhong, Wenwan

    2014-09-05

    Tools capable of measuring binding affinities as well as amenable to downstream sequencing analysis are needed for study of DNA-protein interaction, particularly in discovery of new DNA sequences with affinity to diverse targets. Asymmetrical flow field-flow fractionation (AF4) is an open-channel separation technique that eliminates interference from column packing to the non-covalently bound complex and could potentially be applied for study of macromolecular interaction. The recovery and elution behaviors of the poly(dA)n strand and aptamers in AF4 were investigated. Good recovery of ssDNAs was achieved by judicious selection of the channel membrane with consideration of the membrane pore diameter and the radius of gyration (Rg) of the ssDNA, which was obtained with the aid of a Molecular Dynamics tool. The Rg values were also used to assess the folding situation of aptamers based on their migration times in AF4. The interactions between two ssDNA aptamers and their respective protein components were investigated. Using AF4, near-baseline resolution between the free and protein-bound aptamer fractions could be obtained. With this information, dissociation constants of ∼16nM and ∼57nM were obtained for an IgE aptamer and a streptavidin aptamer, respectively. In addition, free and protein-bound IgE aptamer was extracted from the AF4 eluate and amplified, illustrating the potential of AF4 in screening ssDNAs with high affinity to targets. Our results demonstrate that AF4 is an effective tool holding several advantages over the existing techniques and should be useful for study of diverse macromolecular interaction systems. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Application of asymmetric flow-field flow fractionation to the characterization of colloidal dispersions undergoing aggregation.

    PubMed

    Lattuada, Marco; Olivo, Carlos; Gauer, Cornelius; Storti, Giuseppe; Morbidelli, Massimo

    2010-05-18

    The characterization of complex colloidal dispersions is a relevant and challenging problem in colloidal science. In this work, we show how asymmetric flow-field flow fractionation (AF4) coupled to static light scattering can be used for this purpose. As an example of complex colloidal dispersions, we have chosen two systems undergoing aggregation. The first one is a conventional polystyrene latex undergoing reaction-limited aggregation, which leads to the formation of fractal clusters with well-known structure. The second one is a dispersion of elastomeric colloidal particles made of a polymer with a low glass transition temperature, which undergoes coalescence upon aggregation. Samples are withdrawn during aggregation at fixed times, fractionated with AF4 using a two-angle static light scattering unit as a detector. We have shown that from the analysis of the ratio between the intensities of the scattered light at the two angles the cluster size distribution can be recovered, without any need for calibration based on standard elution times, provided that the geometry and scattering properties of particles and clusters are known. The nonfractionated samples have been characterized also by conventional static and dynamic light scattering to determine their average radius of gyration and hydrodynamic radius. The size distribution of coalescing particles has been investigated also through image analysis of cryo-scanning electron microscopy (SEM) pictures. The average radius of gyration and the average hydrodynamic radius of the nonfractionated samples have been calculated and successfully compared to the values obtained from the size distributions measured by AF4. In addition, the data obtained are also in good agreement with calculations made with population balance equations.

  12. Determining Aqueous Fullerene Particle Size Distributions by Asymmetric Flow Field-Flow Fractionation (AF4) without Surfactants

    EPA Science Inventory

    To determine the behavior of nanoparticles in environmental systems, methods must be developed to measure nanoparticle size. Asymmetric Flow Field Flow Fractionation (AF4) is an aqueous compatible size separation technique which is able to separate particles from 1 nm to 10 µm in...

  13. Determining Aqueous Fullerene Particle Size Distributions by Asymmetric Flow Field-Flow Fractionation (AF4) without Surfactants

    EPA Science Inventory

    To determine the behavior of nanoparticles in environmental systems, methods must be developed to measure nanoparticle size. Asymmetric Flow Field Flow Fractionation (AF4) is an aqueous compatible size separation technique which is able to separate particles from 1 nm to 10 µm in...

  14. Inductively coupled plasma-mass spectrometry as an element-specific detector for field-flow fractionation particle separation

    USGS Publications Warehouse

    Taylor, Howard E.; Garbarino, John R.; Murphy, Deirdre M.; Beckett, Ronald

    1992-01-01

    An inductively coupled plasma-mass spectrometer was used for the quantitative measurement of trace elements In specific,submicrometer size-fraction particulates, separated by sedimentation field-flow fractionation. Fractions were collected from the eluent of the field-flow fractionation centrifuge and nebulized, with a Babington-type pneumatic nebulizer, into an argon inductively coupled plasma-mass spectrometer. Measured Ion currents were used to quantify the major, minor, and trace element composition of the size-separated colloidal (< 1-microm diameter) particulates. The composition of surface-water suspended matter collected from the Yarra and Darling rivers in Australia is presented to illustrate the usefulness of this tool for characterizing environmental materials. An adsorption experiment was performed using cadmium lon to demonstrate the utility for studying the processes of trace metal-suspended sediment interactions and contaminant transport in natural aquatic systems.

  15. Effect of carrier fluid viscosity on retention time and resolution in gravitational field-flow fractionation.

    PubMed

    Lee, Seungho; Kang, Da Young; Park, Miri; Williams, P Stephen

    2011-05-01

    Gravitational field-flow fractionation (GrFFF) is a useful technique for fast separation of micrometer-sized particles. Different sized particles are carried at different velocities by a flow of fluid along an unobstructed thin channel, resulting in a size-based separation. They are confined to thin focused layers in the channel thickness where force due to gravity is exactly opposed by hydrodynamic lift forces (HLF). It has been reported that the HLF are a function of various parameters including the flow rate (or shear rate), the size of the particles, and the density and viscosity of the liquid. The dependence of HLF on these parameters offers a means of altering the equilibrium transverse positions of the particles in GrFFF, and hence their elution times. In this study, the effect of the viscosity of the carrier fluid on the elution behavior (retention, zone broadening, and resolution) of micrometer-sized particles in GrFFF was investigated using polystyrene (PS) latex beads as model particles. In order to change the carrier liquid viscosity without affecting its density, various amounts of (hydroxypropyl) methyl cellulose (HPMC) were added to the aqueous carrier liquid. It was found that particles migrate at faster rates as the carrier viscosity is increased, which confirms the dependence of HLF on viscosity. At the same time, particle size selectivity decreased but peak shape and symmetry for the more strongly retained particles improved. As a result, separation was improved in terms of both the separation time and resolution with increase of carrier viscosity. A theoretical model for plate height in GrFFF is also presented, and its predictions are compared to experimentally measured values.

  16. Impact of carrier fluid composition on recovery of nanoparticles and proteins in flow field flow fractionation.

    PubMed

    Schachermeyer, Samantha; Ashby, Jonathan; Kwon, Minjung; Zhong, Wenwan

    2012-11-16

    Flow field flow fractionation (F4) is an invaluable separation tool for large analytes, including nanoparticles and biomolecule complexes. However, sample loss due to analyte-channel membrane interaction limits extensive usage of F4 at present, which could be strongly affected by the carrier fluid composition. This work studied the impacts of carrier fluid (CF) composition on nanoparticle (NP) recovery in F4, with focus on high ionic strength conditions. Successful analysis of NPs in a biomolecules-friendly environment could expand the applicability of F4 to the developing field of nanobiotechnology. Recovery of the unfunctionalized polystyrene NPs of 199, 102, and 45 nm in CFs with various pH (6.2, 7.4 and 8.2), increasing ionic strength (0-0.1M), and different types of co- and counter-ions, were investigated. Additionally, elution of the 85 nm carboxylate NPs and two proteins, human serum albumin (HSA) and immunoglobulin (IgG), at high ionic strengths (0-0.15M) was investigated. Our results suggested that (1) electrostatic repulsion between the negatively charged NPs and the regenerated cellulose membrane was the main force to avoid particle adsorption on the membrane; (2) larger particles experienced higher attractive force and thus were influenced more by variation in CF composition; and (3) buffers containing weak anions or NPs with weak anion as the surface functional groups provided higher tolerance to the increase in ionic strength, owing to more anions being trapped inside the NP porous structure. Protein adsorption onto the membrane was also briefly investigated in salted CFs, using HSA and IgG. We believe our findings could help to identify the basic carrier fluid composition for higher sample recovery in F4 analysis of nanoparticles in a protein-friendly environment, which will be useful for applying F4 in bioassays and in nanotoxicology studies. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Effect of Ionic and Nonionic Carriers in Electrical Field-Flow Fractionation.

    PubMed

    Ornthai, Mathuros; Siripinyanond, Atitaya; Gale, Bruce K

    2016-02-02

    A major limitation of electrical field-flow fractionation (ElFFF) is the polarization of the electrodes that occurs when using an ionic carrier liquid. As there is great interest in using ElFFF with biological materials and biological materials typically have high ionic strengths and high osmotic concentrations, we explore the effect of concentration for phosphate buffered saline (PBS), a typical ionic medium for biological samples, and for two nonionic materials common in bioparticle analysis: isopropanol (IPA) and sucrose. Their effect on retention and separations in ElFFF for increasing concentrations was observed. The results suggest that modifying the carrier solution with PBS, sucrose, and/or IPA would enable characterization and separation of biological samples in ElFFF. Specifically, changes of elution time and electrical parameters such as current, conductivity, and bulk channel resistance were observed as functions of carrier ionic and osmotic strength for the different carrier additives. PBS can be used in the micromolar range, equivalent to about 0.1% 1× PBS (150 μM). These concentrations are far from the isotonic condition of PBS (∼ 150 mM) that is normally used with biological samples. However, the nonionic additive carriers IPA and sucrose show quality retention even when added in high concentrations. The results show that IPA could be used in ratios up to 60% and that sucrose can be used in concentrations up to 0.3 M. Concentrations of 2% IPA (0.26 M) and 0.30 M sucrose are biologically isotonic conditions (275-299 mOsm/kg), and retention was readily obtained in these conditions using both DC ElFFF and cyclical ElFFF (CyE1FFF). Carriers of this type may make it possible to use ElFFF with biological samples.

  18. Quantum dot agglomerates in biological media and their characterization by asymmetrical flow field-flow fractionation.

    PubMed

    Moquin, Alexandre; Neibert, Kevin D; Maysinger, Dusica; Winnik, Françoise M

    2015-01-01

    The molecular composition of the biological environment of nanoparticles influences their physical properties and changes their pristine physicochemical identity. In order to understand, or predict, the interactions of cells with specific nanoparticles, it is critical to know their size, shape, and agglomeration state not only in their nascent state but also in biological media. Here, we use asymmetrical flow field-flow fractionation (AF4) with on-line multiangle light scattering (MALS), dynamic light scattering (DLS) and UV-Visible absorption detections to determine the relative concentration of isolated nanoparticles and agglomerates in the case of three types of semi-conductor quantum dots (QDs) dispersed in Dulbecco's Modified Eagle Media (DMEM) containing 10% of fetal bovine serum (DMEM-FBS). AF4 analysis also yielded the size and size distribution of the agglomerates as a function of the time of QDs incubation in DMEM-FBS. The preferred modes of internalization of the QDs are assessed for three cell-types, N9 microglia, human hepatocellular carcinoma cells (HepG2) and human embryonic kidney cells (Hek293), by confocal fluorescence imaging of live cells, quantitative determination of the intracellular QD concentration, and flow cytometry. There is an excellent correlation between the agglomeration status of the three types of QDs in DMEM-FBS determined by AF4 analysis and their preferred mode of uptake by the three cell lines, which suggests that AF4 yields an accurate description of the nanoparticles as they encounter cells and advocates its use as a means to characterize particles under evaluation.

  19. Different elution modes and field programming in gravitational field-flow fractionation. Effect of channel angle.

    PubMed

    Park, Mi Ri; Kang, Da Young; Chmelik, Josef; Kang, Namgoo; Kim, Jin Seog; Lee, Seungho

    2008-10-31

    Gravitational field-flow fractionation (GrFFF) has been shown to be useful for separation and characterization of various types of micrometer-sized particles. It has been recognized however that GrFFF is less versatile than other members of FFF because the external field (Earth's gravity) in GrFFF is relatively weak and is not tunable (constant), which makes the force acting on the particles constant. A few approaches have been suggested to control the force acting on particles in GrFFF. They include (1) changing the angle between the Earth's gravitational field and the longitudinal axis of the channel, and (2) the use of carrier liquid having different densities. In the hyperlayer mode of GrFFF, the hydrodynamic lift force (HLF) also act on particles. The existence of HLF allows other means of changing the force acting on the particles in GrFFF. They include (1) the flow rate programming, or (2) the use of channels having non-constant cross-section. In this study, with polystyrene latex beads used as model particles, the channel angle was varied to study its effect on elution parameters (such as selectivity, band broadening and resolution) in the steric or in the hyperlayer mode of GrFFF. In addition, the effects of the channel thickness and the flow rate on the elution parameters were also investigated. It was found that, in the steric mode, the resolution decreases as the flow rate increases due to increased zone broadening despite of the increase in the selectivity. At a constant volumetric flow rate, both the zone broadening and the selectivity increase as the channel thickness increases, resulting in the net increase in the resolution. It was also found that the retention time decreases as the channel angle increases in both up- and down-flow positions. The zone broadening tends to increase almost linearly with the channel angle, while no particular trends were found in selectivity. As a result, the resolution decreases as the channel angle increases.

  20. Chiral magnetic microspheres purified by centrifugal field flow fractionation and microspheres magnetic chiral chromatography for benzoin racemate separation

    PubMed Central

    Tian, Ailin; Qi, Jing; Liu, Yating; Wang, Fengkang; Ito, Yoichiro; Wei, Yun

    2013-01-01

    Separation of enantiomers still remains a challenge due to their identical physical and chemical properties in a chiral environment, and the research on specific chiral selector along with separation techniques continues to be conducted to resolve individual enantiomers. In our laboratory the promising magnetic chiral microspheres Fe3O4@SiO2@cellulose-2, 3-bis (3, 5-dimethylphenylcarbamate) have been developed to facilitate the resolution using both its magnetic property and chiral recognition ability. In our present studies this magnetic chiral selector was first purified by centrifuge field flow fractionation, and then used to separate benzoin racemate by a chromatographic method. Uniform-sized and masking-impurity-removed magnetic chiral selector was first obtained by field flow fractionation with ethanol through a spiral column mounted on the type-J planetary centrifuge, and using the purified magnetic chiral selector, the final chromatographic separation of benzoin racemate was successfully performed by eluting with ethanol through a coiled tube (wound around the cylindrical magnet to retain the magnetic chiral selector as a stationary phase) submerged in dry ice. In addition, an external magnetic field facilitates the recycling of the magnetic chiral selector. PMID:23891368

  1. Influence of secondary preparative parameters and aging effects on PLGA particle size distribution: a sedimentation field flow fractionation investigation.

    PubMed

    Contado, Catia; Vighi, Eleonora; Dalpiaz, Alessandro; Leo, Eliana

    2013-01-01

    Poly(lactic-co-glycolic acid) particles in the 200-400-nm size range were formulated through nanoprecipitation and solvent evaporation methods. Different concentrations of the polymer and stabilizer (Pluronic® F 68) were tested in order to identify the best conditions for making poly(lactic-co-glycolic acid) particles of suitable size, stable in time, and to be used as carriers for brain-targeting drugs. The particles with the best characteristics for delivery system design were those formulated by nanoprecipitation with an organic/water phase ratio of 2:30, a polymer concentration of 25 mg/mL, and a surfactant concentration of 0.83 mg/mL; their surface charge was reasonably negative (approximately -27 mV) and the average size of the almost monodisperse population was roughly 250 nm. Particle characterization was obtained through ζ-potential measurements, scanning electron microscope observations, and particle size distribution determinations; the latter achieved by both photon-correlation spectroscopy and sedimentation field flow fractionation. Sedimentation field flow fractionation, which is considered more reliable than photon-correlation spectroscopy in describing the possible particle size distribution modifications, was used to investigate the effects of 3 months of storage at 4 °C had on the lyophilized particles. Figure Particle size ditribution from the SdFFF and the PCS techniques.

  2. Advanced analysis of polymer emulsions: Particle size and particle size distribution by field-flow fractionation and dynamic light scattering.

    PubMed

    Makan, Ashwell C; Spallek, Markus J; du Toit, Madeleine; Klein, Thorsten; Pasch, Harald

    2016-04-15

    Field flow fractionation (FFF) is an advanced fractionation technique for the analyses of very sensitive particles. In this study, different FFF techniques were used for the fractionation and analysis of polymer emulsions/latexes. As model systems, a pure acrylic emulsion and emulsions containing titanium dioxide were prepared and analyzed. An acrylic emulsion polymerization was conducted, continuously sampled from the reactor and subsequently analyzed to determine the particle size, radius of gyration in specific, of the latex particles throughout the polymerization reaction. Asymmetrical flow field-flow fractionation (AF4) and sedimentation field-flow fractionation (SdFFF), coupled to a multidetector system, multi-angle laser light scattering (MALLS), ultraviolet (UV) and refractive index (RI), respectively, were used to investigate the evolution of particle sizes and particle size distributions (PSDs) as the polymerization progressed. The obtained particle sizes were compared against batch-mode dynamic light scattering (DLS). Results indicated differences between AF4 and DLS results due to DLS taking hydration layers into account, whereas both AF4 and SdFFF were coupled to MALLS detection, hence not taking the hydration layer into account for size determination. SdFFF has additional separation capabilities with a much higher resolution compared to AF4. The calculated radii values were 5 nm larger for SdFFF measurements for each analyzed sample against the corresponding AF4 values. Additionally a low particle size shoulder was observed for SdFFF indicating bimodality in the reactor very early during the polymerization reaction. Furthermore, different emulsions were mixed with inorganic species used as additives in cosmetics and coatings such as TiO2. These complex mixtures of species were analyzed to investigate the retention and particle interaction behavior under different AF4 experimental conditions, such as the mobile phase. The AF4 system was coupled online

  3. Characterization of colloidal phosphorus species in drainage waters from a clay soil using asymmetric flow field-flow fractionation.

    PubMed

    Regelink, Inge C; Koopmans, Gerwin F; van der Salm, Caroline; Weng, Liping; van Riemsdijk, Willem H

    2013-01-01

    Phosphorus transport from agricultural land contributes to eutrophication of surface waters. Pipe drain and trench waters from a grassland field on a heavy clay soil in the Netherlands were sampled before and after manure application. Phosphorus speciation was analyzed by physicochemical P fractionation, and the colloidal P fraction in the dissolved fraction (<0.45 μm) was analyzed by asymmetric flow field-flow fractionation (AF4) coupled to high-resolution inductively coupled plasma-mass spectrometry and ultraviolet diode array detector. When no manure was applied for almost 7 mo, total P (TP) concentrations were low (<21 μmol L), and TP was almost evenly distributed among dissolved reactive P (DRP), dissolved unreactive P (DUP), and particulate P (PP). Total P concentrations increased by a factor of 60 and 4 when rainfall followed shortly after application of cattle slurry or its solid fraction, respectively. Under these conditions, DRP contributed 50% or more to TP. The P speciation within the DUP and PP fractions varied among the different sampling times. Phosphorus associated with dissolved organic matter, probably via cation bridging, comprised a small fraction of DUP at all sampling times. Colloidal P coeluted with clay particles when P application was withheld for almost 7 mo and after application of the solid cattle slurry fraction. At these sampling times, PP correlated well with particulate Fe, Al, and Si, indicating that P is associated with colloidal clay particles. After cattle slurry application, part of DUP was probably present as phospholipids. Physicochemical fractionation combined with AF4 analysis is a promising tool to unravel the speciation of colloidal P in environmental water samples.

  4. Analysis of liposomes using asymmetrical flow field-flow fractionation: separation conditions and drug/lipid recovery.

    PubMed

    Kuntsche, Judith; Decker, Christiane; Fahr, Alfred

    2012-08-01

    Liposomes composed of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol were analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering. In addition to evaluation of fractionation conditions (flow conditions, sample mass, carrier liquid), radiolabeled drug-loaded liposomes were used to determine the liposome recovery and a potential loss of incorporated drug during fractionation. Neither sample concentration nor the cross-flow gradient distinctly affected the size results but at very low sample concentration (injected mass 5 μg) the fraction of larger vesicles was underestimated. Imbalance in the osmolality between the inner and outer aqueous phase resulted in liposome swelling after dilution in hypoosmotic carrier liquids. In contrast, liposome shrinking under hyperosmotic conditions was barely visible. The liposomes themselves eluted completely (lipid recoveries were close to 100%) but there was a loss of incorporated drugs during separation with a strong dependence on the octanol-water partition coefficient of the drug. Whereas corticosterone (partition coefficient ~2) was washed out more or less completely (recovery about 2%), loss of temoporfin (partition coefficient ~9) was only minor (recovery about 80%). All fractionations were well repeatable under the experimental conditions applied in the present study. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Automated frit inlet/frit outlet flow field-flow fractionation for protein characterization with emphasis on polymeric wheat proteins.

    PubMed

    Stevenson, S G; Ueno, T; Preston, K R

    1999-01-01

    A flow field-flow fractionation (FFF) unit fitted with a 254-nm spacer, frit inlet (FI), and frit outlet (FO) was automated for protein analysis by addition of a system controller, autosampler, and computer software to control pumps, sample loading, and data capture. Standard molecular size marker proteins and polymeric wheat storage protein extracts were used to assess the performance of the automated unit. Optimum resolution for these proteins was obtained with a sample inlet flow of 0.2 mL/min, a frit inlet flow (recirculating) of 1.4 mL/min, and a cross-flow (recirculating) of 5 mL/min using 0.05 M acetic acid containing 0.002% FL-70 as a carrier. Use of the FIFO FFF eliminates the requirement for stop-flow relaxation and pressure balancing, results in better reproducibility, and generates a 7-10-fold increase in sensitivity at the detector by concentrating fractions eluting from the channel. These improvements resulted in superior resolution of polymeric wheat protein fractions compared to those obtained previously using a standard channel with manual load and stop-flow relaxation, allowing accurate integration of peak or size range areas. Automation of this system allows unattended sample fractionation and hence markedly increases potential for sample throughput.

  6. Temporal variability of colloidal material in agricultural storm runoff from managed grassland using flow field-flow fractionation.

    PubMed

    Gimbert, Laura J; Worsfold, Paul J

    2009-12-25

    This paper reports the use of flow field-flow fractionation (FlFFF) to determine the temporal variability of colloidal (<1mum) particle size distributions in agricultural runoff waters in a small managed catchment in SW England during storm events. Three storm events of varying intensity were captured and the colloidal material in the runoff analysed by FlFFF. The technique had sufficient sensitivity to determine directly the changing colloidal profile over the 0.08-1.0mum size range in the runoff waters during these storm events. Rainfall, total phosphorus and suspended solids in the bulk runoff samples were also determined throughout one storm and showed significant correlation (P<0.01) with the amount of colloidal material. Whilst there are some uncertainties in the resolution and absolute calibration of the FlFFF profiles, the technique has considerable potential for the quantification of colloidal material in storm runoff waters.

  7. Characterisation of cationic potato starch by asymmetrical flow field-flow fractionation. Influence of ionic strength and degree of substitution.

    PubMed

    Santacruz, Stalin

    2014-06-15

    The properties of a paper sheet depend on the absorption together with the physico-chemical properties of additives used in the paper processing. The effect of ionic strength and degree of substitution of cationic potato starch on the elution pattern of asymmetrical flow field-flow fractionation was analysed. The effect of starch derivatisation, in either dry or wet phase, was also investigated. Average molar mass showed no difference between the starches obtained from the two derivatisation processes. Apparent densities showed that dry cationic starch had higher density than wet cationic starch for a hydrodynamic radius between 50 and 100 nm. Elution times of native and three cationic starches increased when the ionic strength increased from 50 to 100mM. No differences in the molar mass among cationic starches with different degree of substitution suggested no degradation due to a derivatisation process. Large sample loads can be used at 100mM without overloading.

  8. Size- and density-dependent elution of normal and pathological red blood cells by gravitational field-flow fractionation.

    PubMed

    Cardot, P J; Elgéa, C; Guernet, M; Godet, D; Andreux, J P

    1994-04-01

    Elution of normal and pathological human red blood cells (RBCs) was performed by gravitational field-flow fractionation (GFFF). The reproducibility of the retention factor was lower than 10% and elution at high and low flow-rates confirmed the existence of "lifting forces". No direct correlation between size and retention was observed for normal RBCs in the absence of density information. Elution of pathological human RBCs, known to be modified in shape, density and rigidity, was performed. The elution parameters confirmed that the retention mechanism of RBCs is at least density dependent but that other factors can be involved, such as shape or deformity. Moreover, peak profile description parameters (standard deviation and asymmetry) can be qualitatively related to some biophysical parameters. Numerous elution characteristics can be linked to cell properties described in the literature and although GFFF appeared to have limited capabilities in terms of size analysis it appeared to be a versatile tool for studying cell biophysical characteristics.

  9. Field-flow fractionation of chromosomes. Progress report, July 1, 1989--January 31, 1992

    SciTech Connect

    Giddings, J.C.

    1991-09-01

    The work done on this project is divided into two principal areas. The first involves the application of sedimentation/steric FFF to metaphase chromosomes in an attempt to fractionate the chromosomes according to their size. The preparation of chromosomes from a number of organisms was attempted; procedures were finally worked out in collaboration with Los Alamos National Laboratory for the preparation of metaphase chromosomes from Chinese hamster cells. After extensive experimental work was done to identify suitable operating conditions, the partial fractionation of the Chinese hamster chromosomes was achieved. In the second component of the project, flow FFF was applied to the separation of DNA fragments. Figures are provided that show considerable success in the separation of plasmid digests and in the separation of single from double stranded DNA under 10{sup 4} base pairs. Preliminary work was done on DNA fragments having a size greater than 10{sup 4} base pairs. This work has served to establish the inversion point for DNA.

  10. Investigation of zinc oxide particles in cosmetic products by means of centrifugal and asymmetrical flow field-flow fractionation.

    PubMed

    Sogne, Vanessa; Meier, Florian; Klein, Thorsten; Contado, Catia

    2017-09-15

    The dimensional characterization of insoluble, inorganic particles, such as zinc oxide ZnO, dispersed in cosmetic or pharmaceutical formulations, is of great interest considering the current need of declaring the possible presence of nanomaterials on the label of commercial products. This work compares the separation abilities of Centrifugal- and Asymmetrical Flow Field-Flow Fractionation techniques (CF3 and AF4, respectively), equipped with UV-vis, MALS and DLS detectors, in size sorting ZnO particles, both as pristine powders and after their extraction from cosmetic matrices. ZnO particles, bare and superficially modified with triethoxycaprylyl silane, were used as test materials. To identify the most suitable procedure necessary to isolate the ZnO particles from the cosmetic matrix, two O/W and two W/O emulsions were formulated on purpose. The suspensions, containing the extracted particles ZnO, were separated by both Field-Flow Fractionation (FFF) techniques to establish a common analysis protocol, applicable for the analysis of ZnO particles extracted from three commercial products, sold in Europe for the baby skin care. Key aspects of this study were the selection of an appropriate dispersing agent enabling the particles to stay in stable suspensions (>24h)and the use of multiple detectors (UV-vis, MALS and DLS) coupled on-line with the FFF channels, to determine the particle dimensions without using the retention parameters. Between the two FFF techniques, CF3 revealed to be the most robust one, able to sort all suspensions created in this work. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Molecular characterization of solution styrene-butadiene rubber: thermal field-flow fractionation/multi-angle light scattering studies.

    PubMed

    Choi, You Jin; Kim, Sun Tae; Lee, Seung Hwa; Kim, A-Ju; Kwag, Gwanghoon; Lee, Seungho

    2013-11-01

    Solution styrene-butadiene rubber (SSBR) is mainly constituted of a random copolymer of styrene and butadiene. SSBR usually contains microgels, having ultrahigh molecular weight (M>10(7)g/mol), affecting rheological properties of the rubber. Thus, determinations of M and size distribution of these microgels are critical in performance evaluation and control for SSBR. We employ thermal field-flow fractionation (ThFFF), combined with online multi-angle light scattering (MALS), as most suited for characterization of solutions containing the microgels since they can be characterized in toto without removing the microgels from the solution. ThFFF-MALS was applied for characterization of linear and branched SBR materials from various commercial sources, and the results were compared to those from size-exclusion chromatography (SEC). ThFFF provides higher resolution than SEC for high molecular fractions and allowed gel content to be measured. The gel content was determined by subtracting the amount of sol from total injection mass, and was measured to be 10-15%. We infer from the characterization results that the microgel content may not be correlated to the microstructure, the styrene and vinyl content of butadiene but to the fraction of high molecular weight in SSBR. Finally, the macromolecular structure and the content of microgel (larger than about 100nm) were found to significantly affect various rheological parameters such as viscosity, mechanical and dynamic properties. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Application of flow field-flow fractionation for the characterization of macromolecules of biological interest: a review

    PubMed Central

    Qureshi, Rashid Nazir

    2010-01-01

    An overview is given of the recent literature on (bio) analytical applications of flow field-flow fractionation (FlFFF). FlFFF is a liquid-phase separation technique that can separate macromolecules and particles according to size. The technique is increasingly used on a routine basis in a variety of application fields. In food analysis, FlFFF is applied to determine the molecular size distribution of starches and modified celluloses, or to study protein aggregation during food processing. In industrial analysis, it is applied for the characterization of polysaccharides that are used as thickeners and dispersing agents. In pharmaceutical and biomedical laboratories, FlFFF is used to monitor the refolding of recombinant proteins, to detect aggregates of antibodies, or to determine the size distribution of drug carrier particles. In environmental studies, FlFFF is used to characterize natural colloids in water streams, and especially to study trace metal distributions over colloidal particles. In this review, first a short discussion of the state of the art in instrumentation is given. Developments in the coupling of FlFFF to various detection modes are then highlighted. Finally, application studies are discussed and ordered according to the type of (bio) macromolecules or bioparticles that are fractionated. PMID:20957473

  13. A tag-less method for direct isolation of human umbilical vein endothelial cells by gravitational field-flow fractionation.

    PubMed

    Lattuada, Debora; Roda, Barbara; Pignatari, Chiara; Magni, Ruben; Colombo, Federico; Cattaneo, Alessandra; Zattoni, Andrea; Cetin, Irene; Reschiglian, Pierluigi; Bolis, Giorgio

    2013-01-01

    The analysis of cellular and molecular profiles represents a powerful tool in many biomedical applications to identify the mechanisms underlying the pathological changes. The improvement of cellular starting material and the maintenance of the physiological status in the sample preparation are very useful. Human umbilical vein endothelial cells (HUVEC) are a model for prediction of endothelial dysfunction. HUVEC are enzymatically removed from the umbilical vein by collagenase. This method provides obtaining a good sample yield. However, the obtained cells are often contaminated with blood cells and fibroblasts. Methods based on negative selection by in vitro passages or on the use of defined marker are currently employed to isolate target cells. However, these approaches cannot reproduce physiological status and they require expensive instrumentation. Here we proposed a new method for an easy, tag-less and direct isolation of HUVEC from raw umbilical cord sample based on the gravitational field-flow fractionation (GrFFF). This is a low-cost, fully biocompatible method with low instrumental and training investments for flow-assisted cell fractionation. The method allows obtaining pure cells without cell culture procedures as starting material for further analysis; for example, a proper amount of RNA can be extracted. The approach can be easily integrated into clinical and biomedical procedures.

  14. Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows. Part II. Experimental evaluation.

    PubMed

    Magnusson, Emma; Håkansson, Andreas; Janiak, John; Bergenståhl, Björn; Nilsson, Lars

    2012-08-31

    In this study we investigate the effect of programmed cross-flows on the error in the hydrodynamic radii (r(h)) determination with asymmetrical flow field-flow fractionation (AsFlFFF). Three different standard polystyrene particles (nominal radii of 30 and 40 and 50 nm) are fractionated with exponentially and linearly decaying cross-flows with different decay rates. Hydrodynamic radii are calculated according to retention theory including steric effects. Rapid decay is expected to give rise to systematic deviations in r(h) determination. The error in r(h) was found to be small when decay rates with half-lives longer than 6 min were used, whereas steeper decays could give rise to errors as high as 16% of the particle size. The error is often explained in terms of secondary relaxation. However, comparisons show that experimental errors are significantly larger than what would be expected due to secondary relaxation, suggesting that other factors also have to be considered in order to fully understand deviations for rapidly decaying cross-flow.

  15. Characterization of silver nanoparticles using flow-field flow fractionation interfaced to inductively coupled plasma mass spectrometry.

    PubMed

    Poda, A R; Bednar, A J; Kennedy, A J; Harmon, A; Hull, M; Mitrano, D M; Ranville, J F; Steevens, J

    2011-07-08

    The ability to detect and identify the physiochemical form of contaminants in the environment is important for degradation, fate and transport, and toxicity studies. This is particularly true of nanomaterials that exist as discrete particles rather than dissolved or sorbed contaminant molecules in the environment. Nanoparticles will tend to agglomerate or dissolve, based on solution chemistry, which will drastically affect their environmental properties. The current study investigates the use of field flow fractionation (FFF) interfaced to inductively coupled plasma-mass spectrometry (ICP-MS) as a sensitive and selective method for detection and characterization of silver nanoparticles. Transmission electron microscopy (TEM) is used to verify the morphology and primary particle size and size distribution of precisely engineered silver nanoparticles. Subsequently, the hydrodynamic size measurements by FFF are compared to dynamic light scattering (DLS) to verify the accuracy of the size determination. Additionally, the sensitivity of the ICP-MS detector is demonstrated by fractionation of μg/L concentrations of mixed silver nanoparticle standards. The technique has been applied to nanoparticle suspensions prior to use in toxicity studies, and post-exposure biological tissue analysis. Silver nanoparticles extracted from tissues of the sediment-dwelling, freshwater oligochaete Lumbriculus variegatus increased in size from approximately 31-46nm, indicating a significant change in the nanoparticle characteristics during exposure.

  16. Size-based analysis of incinerator fly ash using gravitational SPLITT fractionation, sedimentation field-flow fractionation, and inductively coupled plasma-atomic emission spectroscopy.

    PubMed

    Kim, Won-Suk; Park, Mira; Lee, Dai Woon; Moon, Myeong Hee; Lim, Heungbin; Lee, Seungho

    2004-02-01

    Fly ash has been regarded as hazardous because of its high adsorption of toxic organic and/or inorganic pollutants. Fly ash is also known to have broad distributions of different chemical and physical properties, such as size and density. In this study, fly ash emitted from a solid waste incinerator was pre-fractionated into six sub-populations by use of gravitational SPLITT fractionation (GSF). The GSF fractions were then analyzed by sedimentation field-flow fractionation (SdFFF) and ICP-AES. SdFFF analysis showed the fly ash has a broad size distribution ranging from a few nanometers up to about 50 microm. SdFFF results were confirmed by electron microscopy. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis of the GSF fractions showed the fly-ash particles contain a variety of inorganic elements including Ca, Si, Mg, Fe, and Pb. The most abundant in fly ash was Ca, followed by Si then Mg. No correlations were found between trace element concentration and particle size.

  17. Study on aggregation behavior of Cytochrome C-conjugated silver nanoparticles using asymmetrical flow field-flow fractionation.

    PubMed

    Kim, Sun Tae; Lee, Yong-Ju; Hwang, Yu-Sik; Lee, Seungho

    2015-01-01

    In this study, 40 nm silver nanoparticles (AgNPs) were synthesized using the citrate reduction method and then the surface of AgNPs was modified by conjugating Cytochrome C (Cyto C) to improve stability and to enhance bioactivity and biocompatibility of AgNPs. It is known that Cyto C may undergo conformational changes under various conditions of pH, temperature, ionic strength, etc., resulting in aggregation of the particles. These parameters also affect the size and size distribution of Cyto C-conjugated AgNPs (Cyto C-AgNP). ζ-potential measurement revealed that the adsorption of Cyto C on the surface of AgNPs is saturated at the molar ratio [Cyto C]/[AgNPs] above about 300. Asymmetrical flow field-flow fractionation (AsFlFFF) analysis showed that hydrodynamic diameter of AgNPs increases by about 4 nm when the particle is saturated by Cyto C. The aggregation behavior of Cyto C-AgNP at various conditions of pH, temperature and ionic strength were investigated using AsFlFFF and UV-vis spectroscopy. It was found that the aggregation of Cyto C-AgNP increases with decreasing pH, increasing temperature and ionic strength due to denaturation of Cyto C on AgNPs and reduction in the thickness of electrostatic double layer on the surface of Cyto C-AgNP.

  18. Numerical analysis of a dielectrophoresis field-flow fractionation device for the separation of multiple cell types.

    PubMed

    Shamloo, Amir; Kamali, Ali

    2017-08-10

    In this study, a dielectrophoresis field-flow fractionation device was analyzed using a numerical simulation method and the behaviors of a set of different cells were investigated. By reducing the alternating current frequency of the electrodes from the value used in the original setup configuration and increasing the number of exit channels, total discrimination in cell trajectories and subsequent separation of four cell types were achieved. Cells were differentiated based on their size and dielectric response that are represented in their real part of Clausius-Mossotti factor at different frequencies. A number of novel designs were also proposed based on the original setup configuration. It was seen that by reducing the length of the main channel and the number of electrodes at low frequencies and not changing the inlet flow velocities, cell separation was still achieved successfully, although with a slightly larger electrode voltage. The shorter main channel decreased the residence time for the cells on the chip and also reduced the overall size of the device-these were improvements over the original design. The obtained results can be used to analyze other cell types by knowing their size and dielectric properties to design geometries that can ensure separation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Retention behavior of microparticles in gravitational field-flow fractionation (GrFFF): effect of ionic strength.

    PubMed

    Woo, In Suk; Jung, Euo Chang; Lee, Seungho

    2015-01-01

    Retention behavior of micron-sized particles in gravitational field-flow fractionation (GrFFF) was studied in this study. Effects of ionic strength and flow rate as well as the viscosity of the GrFFF carrier liquid was investigated on the size-based selectivity (Sd), retention ratio (R), and plate height (H) of micron-sized particles using polystyrene latex beads as model particles. It was found that the retention ratio of microparticles increases with increasing flow rate or the viscosity of the carrier liquid as the particles are forced away from the accumulation wall by increased hydrodynamic lift forces (HLF). On the other hand, the retention time increases (retention ratio decreases) with increasing ionic strength of the carrier liquid at the same flow rate, due to decreased repulsive interaction between the particles and the channel accumulation wall (glass in this study) allowing the particles approach closer to the wall. Results suggest the ionic strength of the carrier liquid plays a critical role in determining retention of microparticles in GrFFF as well as the viscosity or the flow rate of the carrier liquid. It was found that the resolution and the separation time could be improved by increasing the carrier viscosity and by carefully adjusting the ionic strength of the carrier liquid. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Effects of comprehensive function of factors on retention behavior of microparticles in gravitational field-flow fractionation.

    PubMed

    Guo, Shuang; Qiu, Bai-Ling; Zhu, Chen-Qi; Yang, Ya-Ya Gao; Wu, Di; Liang, Qi-Hui; Han, Nan-Yin

    2016-09-15

    Gravitational field-flow fractionation (GrFFF) is a useful technique for separation and characterization for micrometer-sized particles. Elution behavior of micrometer-sized particles in GrFFF was researched in this study. Particles in GrFFF channel are subject to hydrodynamic lift forces (HLF), fluid inertial forces and gravity, which drive them to different velocities by carrier flow, resulting in a size-based separation. Effects of ionic strength, flow rate and viscosity as well as methanol were investigated using polystyrene latex beads as model particles. This study is devoted to experimental verification of the effect of every factor and their comprehensive function. All experiments were performed to show isolated influence of every variable factor. The orthogonal design test was used to evaluate various factors comprehensively. Results suggested that retention ratio of particles increases with increasing flow rate or the viscosity of carrier liquid by adjusting external forces acting on particles. In addition, retention ratio increases as ionic strength decreases because of decreased electrostatic repulsion between particles and channel accumulation wall. As far as methanol, there is no general trend due to the change of both density and viscosity. On the basis of orthogonal design test it was found that viscosity of carrier liquid plays a significant role in determining resolution of micrometer-sized particles in GrFFF. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Aggregation behavior of fullerenes in aqueous solutions: a capillary electrophoresis and asymmetric flow field-flow fractionation study.

    PubMed

    Astefanei, Alina; Núñez, Oscar; Galceran, Maria Teresa; Kok, Wim Th; Schoenmakers, Peter J

    2015-10-01

    In this work, the electrophoretic behavior of hydrophobic fullerenes [buckminsterfullerene (C60), C70, and N-methyl-fulleropyrrolidine (C60-pyrr)] and water-soluble fullerenes [fullerol (C60(OH)24); polyhydroxy small gap fullerene, hydrated (C120(OH)30); C60 pyrrolidine tris acid (C60-pyrr tris acid); and (1,2-methanofullerene C60)-61-carboxylic acid (C60CHCOOH)] in micellar electrokinetic capillary chromatography (MECC) was evaluated. The aggregation behavior of the water-soluble compounds in MECC at different buffer and sodium dodecyl sulfate (SDS) concentrations and pH values of the background electrolyte (BGE) was studied by monitoring the changes observed in the electrophoretic pattern of the peaks. Broad and distorted peaks that can be attributed to fullerene aggregation were obtained in MECC which became narrower and more symmetric by working at low buffer and SDS concentrations (below the critical micelle concentration, capillary zone electrophoresis (CZE) conditions). For the characterization of the suspected aggregates formed (size and shape), asymmetrical flow field-flow fractionation (AF4) and transmission electron microscopy (TEM) were used. The results showed that the increase in the buffer concentration promoted the aggregation of the particles, while the presence of SDS micelles revealed multiple peaks corresponding to particles of different aggregation degrees. Furthermore, MECC has been applied for the first time for the analysis of C60 in two different cosmetic products (i.e., anti-aging serum and facial mask).

  2. Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows. Part I. A theoretical approach.

    PubMed

    Håkansson, Andreas; Magnusson, Emma; Bergenståhl, Björn; Nilsson, Lars

    2012-08-31

    Direct determination of hydrodynamic radius from retention time is an advantage of the field-flow fractionation techniques. However, this is not always completely straight forward since non-idealities exist and assumptions have been made in deriving the retention equations. In this study we investigate the effect on accuracy from two factors: (1) level of sophistication of the equations used to determine channel height from a calibration experiment and (2) the influence of secondary relaxation on the accuracy of hydrodynamic radius determination. A new improved technique for estimating the channel height from calibration experiments is suggested. It is concluded that severe systematic error can arise if the most common channel height equations are used and an alternative more rigorous approach is described. For secondary relaxation it is concluded that this effect increases with the cross-flow decay rate. The secondary relaxation effect is quantified for different conditions. This is part one of two. In the second part the determination of hydrodynamic radius are evaluated experimentally under similar conditions.

  3. Complementary use of flow and sedimentation field-flow fractionation techniques for size characterizing biodegradable poly(lactic acid) nanospheres.

    PubMed

    Contado, Catia; Dalpiaz, Alessandro; Leo, Eliana; Zborowski, Maciej; Williams, P Stephen

    2007-07-20

    Poly(lactic acid) (PLA) nanoparticles were synthesized using a modified evaporation method, testing two different surfactants (sodium cholate and Pluronic F68) for the process. During their formulation the prodrug 5'-octanoyl-CPA (Oct-CPA) of the anti-ischemic N(6)-cyclopentyladenosine (CPA) was encapsulated. Three different purification methods were compared with respect to the influence of surfactant on the size characteristics of the final nanoparticle product. Flow and sedimentation field-flow fractionation techniques (FlFFF and SdFFF, respectively) were used to size characterize the five poly(lactic acid) particle samples. Two different combinations of carrier solution (mobile phase) were employed in the FlFFF analyses, while a solution of poly(vinyl alcohol) was used as mobile phase for the SdFFF runs. The separation performances of the two techniques were compared and the particle size distributions (PSDs), derived from the fractograms, were interpreted with the support of observations by scanning electron microscopy. Some critical aspects, such as the carrier choice and the channel thickness determination for the FlFFF, have been investigated. This is the first comprehensive comparison of the two FFF techniques for characterizing non-standard particulate materials. The two FFF techniques proved to be complementary and gave good, congruent and very useful information on the size distributions of the five poly(lactic acid) particle samples.

  4. Complementary use of flow and sedimentation field-flow fractionation techniques for size characterizing biodegradable poly(lactic acid) nanospheres

    PubMed Central

    Contado, Catia; Dalpiaz, Alessandro; Leo, Eliana; Zborowski, Maciej; Williams, P. Stephen

    2009-01-01

    Poly(lactic acid) nanoparticles were synthesized using a modified evaporation method, testing two different surfactants (sodium cholate and Pluronic F68) for the process. During their formulation the prodrug 5′-octanoyl-CPA (Oct-CPA) of the antiischemic N6-cyclopentyladenosine (CPA) was encapsulated. Three different purification methods were compared with respect to the influence of surfactant on the size characteristics of the final nanoparticle product. Flow and sedimentation field-flow fractionation techniques (FlFFF and SdFFF, respectively) were used to size characterize the five poly(lactic acid) particle samples. Two different combinations of carrier solution (mobile phase) were employed in the FlFFF analyses, while a solution of poly(vinyl alcohol) was used as mobile phase for the SdFFF runs. The separation performances of the two techniques were compared and the particle size distributions, derived from the fractograms, were interpreted with the support of observations by scanning electron microscopy. Some critical aspects, such as the carrier choice and the channel thickness determination for the FlFFF, have been investigated. This is the first comprehensive comparison of the two FFF techniques for characterizing non standard particulate materials. The two FFF techniques proved to be complementary and gave good, congruent and very useful information on the size distributions of the five poly(lactic acid) particle samples. PMID:17482199

  5. Study on steric transition in asymmetrical flow field-flow fractionation and application to characterization of high-energy material.

    PubMed

    Dou, Haiyang; Lee, Yong-Ju; Jung, Euo Chang; Lee, Byung-Chul; Lee, Seungho

    2013-08-23

    In field-flow fractionation (FFF), there is the 'steric transition' phenomenon where the sample elution mode changes from the normal to steric/hyperlayer mode. Accurate analysis by FFF requires understanding of the steric transition phenomenon, particularly when the sample has a broad size distribution, for which the effect by combination of different modes may become complicated to interpret. In this study, the steric transition phenomenon in asymmetrical flow FFF (AF4) was studied using polystyrene (PS) latex beads. The retention ratio (R) gradually decreases as the particle size increases (normal mode) and reaches a minimum (Ri) at diameter around 0.5μm, after which R increases with increasing diameter (steric/hyperlayer mode). It was found that the size-based selectivity (Sd) tends to increase as the channel thickness (w) increases. The retention behavior of cyclo-1,3,5-trimethylene-2,4,6-trinitramine (commonly called 'research department explosive' (RDX)) particles in AF4 was investigated by varying experimental parameters including w and flow rates. AF4 showed a good reproducibility in size determination of RDX particles with the relative standard deviation of 4.1%. The reliability of separation obtained by AF4 was evaluated by transmission electron microscopy (TEM).

  6. Simultaneous sample preconcentration and matrix removal using field-flow fractionation coupled to inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Al-Ammar, Assad; Siripinyanond, Atitaya; Barnes, Ramon M.

    2001-10-01

    An on-channel sample preconcentration-matrix removal arrangement, based on coupling field-flow fractionation (FFF) to inductively coupled plasma mass spectrometry (ICP-MS), has been constructed for on-line sample pretreatment ICP-MS trace element determination. A commercial FFF system is modified to incorporate an on-channel preconcentration procedure allowing injection of up to 50 ml of sample, which could be preconcentrated by 50-1400 fold. A high molecular weight complexing agent added to the sample forms strong complexes with the measured trace analytes but not with the sample matrix. When the sample-complexing agent mixture is introduced to the FFF unit, the uncomplexed matrix element is removed by permeation through a membrane that separates the FFF sample compartment. The trace analytes remain in the FFF channel, because their high molecular weight complexes do not permeate through the membrane. Preconcentration and matrix elimination occur simultaneously. The matrix-free, preconcentrated sample is introduced directly to the ICP-MS nebulizer. The method was tested using 10-ml sample aliquots that contain As, Cd, Cu, Mo, Pb, Re, Sn, Te, Tl, Y, Zn and Zr analytes and 5000 mg l -1 Ca or Na matrices and ethylene imine polymer complexing agent. Copper and Re isotopic ratio values in reference standards also were determined after preconcentration and matrix element removal.

  7. Sedimentation field flow fractionation of immunoglobulin A coated polystyrene beads. Influence of carrier composition on complex characterization.

    PubMed

    Contado, Catia; Bregola, Letizia; Dondi, Francesco

    2007-10-26

    The amount of immunoglobulin A (IgA) adsorbed on the surface of two different samples of polystyrene (PS) microbeads was evaluated using differential sedimentation field flow fractionation (SdFFF) analyses. For the first time, the SdFFF separations obtained by using, as mobile phase, solutions common to many biochemical procedures and applications have been compared and discussed. Good separation results were achieved in the different carriers, and the SdFFF gave equivalent mass per particle values in all carriers provided that the pH and ionic strength conditions of the eluents were well controlled. The IgA adsorption process onto PS occurred by maintaining unaltered the capacity of the PS-IgA substrate to selectively recognize anti-IgA (aIgA), as proven by elution of the ternary complex PS-IgA-aIgA and from the monitored lack of reaction when the PS-IgA was placed in contact with aIgE.

  8. A novel method to detect unlabeled inorganic nanoparticles and submicron particles in tissue by sedimentation field-flow fractionation

    PubMed Central

    Deering, Cassandra E; Tadjiki, Soheyl; Assemi, Shoeleh; Miller, Jan D; Yost, Garold S; Veranth, John M

    2008-01-01

    A novel methodology to detect unlabeled inorganic nanoparticles was experimentally demonstrated using a mixture of nano-sized (70 nm) and submicron (250 nm) silicon dioxide particles added to mammalian tissue. The size and concentration of environmentally relevant inorganic particles in a tissue sample can be determined by a procedure consisting of matrix digestion, particle recovery by centrifugation, size separation by sedimentation field-flow fractionation (SdFFF), and detection by light scattering. Background Laboratory nanoparticles that have been labeled by fluorescence, radioactivity, or rare elements have provided important information regarding nanoparticle uptake and translocation, but most nanomaterials that are commercially produced for industrial and consumer applications do not contain a specific label. Methods Both nitric acid digestion and enzyme digestion were tested with liver and lung tissue as well as with cultured cells. Tissue processing with a mixture of protease enzymes is preferred because it is applicable to a wide range of particle compositions. Samples were visualized via fluorescence microscopy and transmission electron microscopy to validate the SdFFF results. We describe in detail the tissue preparation procedures and discuss method sensitivity compared to reported levels of nanoparticles in vivo. Conclusion Tissue digestion and SdFFF complement existing techniques by precisely identifying unlabeled metal oxide nanoparticles and unambiguously distinguishing nanoparticles (diameter<100 nm) from both soluble compounds and from larger particles of the same nominal elemental composition. This is an exciting capability that can facilitate epidemiological and toxicological research on natural and manufactured nanomaterials. PMID:19055780

  9. Optimization of experimental conditions for the separation of small and large starch granules by gravitational field-flow fractionation.

    PubMed

    Janousková, J; Budinská, M; Plocková, J; Chmelík, J

    2001-04-20

    Separation of small and large barley starch granules by gravitational field-flow fractionation was investigated from the point of view of sample pre-treatment, amount of injected sample, and elution conditions. The sample pre-treatment study resulted in the conclusion that it is reasonable to soak the starch granules for at least 24 h prior to separation. The experiments with different amounts of injected sample show that it is possible to increase as well as decrease twofold the sample amount usually used without any change in retention ratios. The implementation of flow-rate gradients for elution of the starch granules reduced total separation time. However, the applied flow-rate gradients did not improve the resolution of peaks A and B compared with the generally used constant flow-rate. Thus, for barley starch granules, the constant flow-rates within the range from 0.8 to 1.0 ml/min seem to provide the best compromise of total separation time, peak resolution and instrumental expense.

  10. Development and evaluation of methods for starch dissolution using asymmetrical flow field-flow fractionation. Part II: Dissolution of amylose.

    PubMed

    Perez-Rea, Daysi; Bergenståhl, Björn; Nilsson, Lars

    2016-02-01

    In this paper, we investigate whether dissolution in water under autoclaving conditions (140 °C, 20 min) or in dimethyl sulfoxide, DMSO (100 °C, 1 h), is preferable for characterization of amylose. Two types of amylose, potato and maize, were dissolved either in water using an autoclave or in DMSO. On the aqueous solutions obtained, the extent of molecular dissolution of the sample (referred to as the dissolution yield) was determined by enzymatic analysis as well as the molecular properties, such as molar mass and root-mean-square radius, obtained with asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and differential refractive index detection (AF4-MALS-dRI). The results showed that both dissolution methods are efficient at dissolving amylose. However, AF4-MALS-dRI analysis revealed substantial differences. Amylose aqueous solutions obtained by dissolution in DMSO were relatively stable over time, but the dissolution method in autoclave caused some degradation of the molecules, and their solutions display a high tendency to retrograde.

  11. Field-flow fractionation: An efficient approach for matrix removal of soil extract for inductively coupled plasma optical emission spectrometry

    NASA Astrophysics Data System (ADS)

    Sangsawong, Supharart; Waiyawat, Weerawan; Shiowatana, Juwadee; Siripinyanond, Atitaya

    2011-06-01

    An on-line coupling between a continuous-flow sequential extraction (CFSE) unit and flow field-flow fractionation with cross flow matrix removal (FlFFF/CFM) with ICP-OES detection was developed for determination of metal leachability from soil. The use of high concentration of Mg(NO 3) 2 in exchangeable phase can cause undesirable matrix effects by shifting ionization equilibrium in the plasma, etc., resulting in a clear need for matrix removal. Therefore, the capability of FlFFF/CFM to remove Mg matrix ion from soil extract was evaluated. Poly(ethylene imine) (PEI) having molecular weight of 25,000 Da was added to form complexes with analyte elements (Cu, Mn, Pb, and Zn) but not the matrix element (Mg). The free Mg matrix ions were then removed by filtering off through the ultrafiltration membrane, having a 1000-Da molecular weight cut-off, inside the FlFFF channel. With the use of FlFFF/CFM, matrix removal efficiency was approximately 83.5%, which was equivalent to approximately 6-fold dilution of the matrix ion. The proposed hyphenated system of CFSE and FlFFF/CFM with ICP-OES detection was examined for its reliability by checking with SRM 2710 (a highly contaminated soil from Montana). The metal contents determined by the proposed method were not significantly different (at 95% confidence) from the certified values.

  12. Monitoring the Erosion of Hydrolytically-Degradable Nanogels via Multiangle Light Scattering Coupled to Asymmetrical Flow Field-Flow Fractionation

    PubMed Central

    Smith, Michael H.; South, Antoinette B.; Gaulding, Jeffrey C.; Lyon, L. Andrew

    2009-01-01

    We describe the synthesis and characterization of degradable nanogels that display bulk erosion under physiologic conditions (pH = 7.4, 37 °C). Erodible poly(N-isopropylmethacrylamide) nanogels were synthesized by copolymerization with N,O-(dimethacryloyl)hydroxylamine, a cross-linker previously used in the preparation of non-toxic and biodegradable bulk hydrogels. To monitor particle degradation, we employed multiangle light scattering and differential refractometry detection following asymmetrical flow field-flow fractionation. This approach allowed the detection of changes in nanogel molar mass and topology as a function of both temperature and pH. Particle erosion was evident from both an increase in nanogel swelling and a decrease in scattering intensity as a function of time. Following these analyses, the samples were recovered for subsequent characterization by direct particle tracking, which yields hydrodynamic size measurements and enables number density determination. Additionally, we confirmed the conservation of nanogel stimuli-responsivity through turbidity measurements. Thus, we have demonstrated the synthesis of degradable nanogels that erode under conditions and on timescales that are relevant for many drug delivery applications. The combined separation and light scattering detection method is demonstrated to be a versatile means to monitor erosion and should also find applicability in the characterization of other degradable particle constructs. PMID:20000662

  13. Online Coupling of Flow-Field Flow Fractionation and Single Particle Inductively Coupled Plasma-Mass Spectrometry: Characterization of Nanoparticle Surface Coating Thickness and Aggregation State

    EPA Science Inventory

    Surface coating thickness and aggregation state have strong influence on the environmental fate, transport, and toxicity of engineered nanomaterials. In this study, flow-field flow fractionation coupled on-line with single particle inductively coupled plasma-mass spectrometry i...

  14. Online Coupling of Flow-Field Flow Fractionation and Single Particle Inductively Coupled Plasma-Mass Spectrometry: Characterization of Nanoparticle Surface Coating Thickness and Aggregation State

    EPA Science Inventory

    Surface coating thickness and aggregation state have strong influence on the environmental fate, transport, and toxicity of engineered nanomaterials. In this study, flow-field flow fractionation coupled on-line with single particle inductively coupled plasma-mass spectrometry i...

  15. Feasibility study of red blood cell debulking by magnetic field-flow fractionation with step-programmed flow

    PubMed Central

    Moore, Lee R.; Williams, P. Stephen; Nehl, Franziska; Abe, Koji; Chalmers, Jeffrey J.; Zborowski, Maciej

    2013-01-01

    Emerging applications of rare cell separation and analysis, such as separation of mature red blood cells from hematopoietic cell cultures require efficient methods of red blood cell (RBC) debulking. We have tested the feasibility of magnetic RBC separation as an alternative to centrifugal separation using an approach based on the mechanism of magnetic field-flow fractionation (MgFFF). A specially designed permanent magnet assembly generated a quadrupole field having a maximum field of 1.68 T at the magnet pole tips, zero field at the aperture axis, and a nearly constant radial field gradient of 1.75 T/mm (with a negligible angular component) inside a cylindrical aperture of 1.9 mm (diameter) and 76 mm (length). The cell samples included high-spin hemoglobin RBCs obtained by chemical conversion of hemoglobin to methemoglobin (met RBC) or by exposure to anoxic conditions (deoxy RBC), low-spin hemoglobin obtained by exposure of RBC suspension to ambient air (oxy RBC), and mixtures of deoxy RBC and cells from a KG-1a white blood cell (WBC) line. The observation that met RBCs did not elute from the channel at the lower flow rate of 0.05 mL/min applied for 15 min but quickly eluted at the subsequent higher flow rate of 2.0 mL/min was in agreement with FFF theory. The well-defined experimental conditions (precise field and flow characteristics) and a well-established FFF theory verified by studies with model cell systems provided us with a strong basis for making predictions about potential practical applications of the magnetic RBC separation. PMID:24141316

  16. Ionic strength effect on molecular structure of hyaluronic acid investigated by flow field-flow fractionation and multiangle light scattering.

    PubMed

    Kim, Bitnara; Woo, Sohee; Park, Young-Soo; Hwang, Euijin; Moon, Myeong Hee

    2015-02-01

    This study describes the effect of ionic strength on the molecular structure of hyaluronic acid (HA) in an aqueous solution using flow field-flow fractionation and multiangle light scattering (FlFFF-MALS). Sodium salts of HA (NaHA) raw materials (∼2 × 10(6) Da) dispersed in different concentrations of NaCl prepared by repeated dilution/ultrafiltration procedures were examined in order to study conformational changes in terms of the relationship between the radius of gyration and molecular weight (MW) and molecular weight distribution (MWD) of NaHA in solution. This was achieved by varying the ionic strength of the carrier solution used in a frit-inlet asymmetrical FlFFF (FIAF4) channel. Experiments showed that the average MW of NaHA increased as the ionic strength of the NaHA solution decreased due to enhanced entanglement or aggregation of HA molecules. Relatively large molecules (greater than ∼5 MDa) did not show a large increase in RMS radius value as the NaCl concentration decreased. Conversely, smaller species showed larger changes, suggesting molecular expansion at lower ionic strengths. When the ionic strength of the FlFFF carrier solution was decreased, the HA species in a salt-rich solution (0.2 M NaCl) underwent rapid molecular aggregation during FlFFF separation. However, when salt-depleted HA samples (I = 4.66∼0.38 mM) were analyzed with FFF carrier solutions of a high ionic strength, the changes in both molecular structure and size were somewhat reversible, although there was a delay in correction of the molecular structure.

  17. Field-flow fractionation as analytical technique for the characterization of dry yeast: correlation with wine fermentation activity.

    PubMed

    Sanz, Ramsés; Galceran, Ma Teresa; Puignou, Lluís

    2003-01-01

    Important oenological properties of wine depend on the winemaking yeast used in the fermentation process. There is considerable controversy about the quality of yeast, and a simple and cheap analytical methodology for quality control of yeast is needed. Gravitational field flow fractionation (GFFF) was used to characterize several commercial active dry wine yeasts from Saccharomyces cerevisiae and Saccharomyces bayanus and to assess the quality of the raw material before use. Laboratory-scale fermentations were performed using two different S. cerevisiae strains as inocula, and GFFF was used to follow the behavior of yeast cells during alcoholic fermentation. The viable/nonviable cell ratio was obtained by flow cytometry (FC) using propidium iodide as fluorescent dye. In each experiment, the amount of dry wine yeast to be used was calculated in order to provide the same quantity of viable cells. Kinetic studies of the fermentation process were performed controlling the density of the must, from 1.071 to 0.989 (20/20 density), and the total residual sugars, from 170 to 3 g/L. During the wine fermentation process, differences in the peak profiles obtained by GFFF between the two types of commercial yeasts that can be related with the unlike cell growth were observed. Moreover, the strains showed different fermentation kinetic profiles that could be correlated with the corresponding fractograms monitored by GFFF. These results allow optimism that sedimentation FFF techniques could be successfully used for quality assessment of the raw material and to predict yeast behavior during yeast-based bioprocesses such as wine production.

  18. Feasibility study of red blood cell debulking by magnetic field-flow fractionation with step-programmed flow.

    PubMed

    Moore, Lee R; Williams, P Stephen; Nehl, Franziska; Abe, Koji; Chalmers, Jeffrey J; Zborowski, Maciej

    2014-02-01

    Emerging applications of rare cell separation and analysis, such as separation of mature red blood cells from hematopoietic cell cultures, require efficient methods of red blood cell (RBC) debulking. We have tested the feasibility of magnetic RBC separation as an alternative to centrifugal separation using an approach based on the mechanism of magnetic field-flow fractionation (MgFFF). A specially designed permanent magnet assembly generated a quadrupole field having a maximum field of 1.68 T at the magnet pole tips, zero field at the aperture axis, and a nearly constant radial field gradient of 1.75 T/mm (with a negligible angular component) inside a cylindrical aperture of 1.9 mm (diameter) and 76 mm (length). The cell samples included high-spin hemoglobin RBCs obtained by chemical conversion of hemoglobin to methemoglobin (met RBC) or by exposure to anoxic conditions (deoxy RBC), low-spin hemoglobin obtained by exposure of RBC suspension to ambient air (oxy RBC), and mixtures of deoxy RBC and cells from a KG-1a white blood cell (WBC) line. The observation that met RBCs did not elute from the channel at the lower flow rate of 0.05 mL/min applied for 15 min but quickly eluted at the subsequent higher flow rate of 2.0 mL/min was in agreement with FFF theory. The well-defined experimental conditions (precise field and flow characteristics) and a well-established FFF theory verified by studies with model cell systems provided us with a strong basis for making predictions about potential practical applications of the magnetic RBC separation.

  19. Asymmetrical flow field-flow fractionation with multi-angle light scattering and quasi-elastic light scattering for characterization of polymersomes: comparison with classical techniques.

    PubMed

    Till, Ugo; Gaucher-Delmas, Mireille; Saint-Aguet, Pascale; Hamon, Glenn; Marty, Jean-Daniel; Chassenieux, Christophe; Payré, Bruno; Goudounèche, Dominique; Mingotaud, Anne-Françoise; Violleau, Frédéric

    2014-12-01

    Polymersomes formed from amphiphilic block copolymers, such as poly(ethyleneoxide-b-ε-caprolactone) (PEO-b-PCL) or poly(ethyleneoxide-b-methylmethacrylate), were characterized by asymmetrical flow field-flow fractionation coupled with quasi-elastic light scattering (QELS), multi-angle light scattering (MALS), and refractive index detection, leading to the determination of their size, shape, and molecular weight. The method was cross-examined with more classical ones, like batch dynamic and static light scattering, electron microscopy, and atomic force microscopy. The results show good complementarities between all the techniques; asymmetrical flow field-flow fractionation being the most pertinent one when the sample exhibits several different types of population.

  20. Polysaccharide characterization by hollow-fiber flow field-flow fractionation with on-line multi-angle static light scattering and differential refractometry.

    PubMed

    Pitkänen, Leena; Striegel, André M

    2015-02-06

    Accurate characterization of the molar mass and size of polysaccharides is an ongoing challenge, oftentimes due to architectural diversity but also to the broad molar mass (M) range over which a single polysaccharide can exist and to the ultra-high M of many polysaccharides. Because of the latter, many of these biomacromolecules experience on-column, flow-induced degradation during analysis by size-exclusion and, even, hydrodynamic chromatography (SEC and HDC, respectively). The necessity for gentler fractionation methods has, to date, been addressed employing asymmetric flow field-flow fractionation (AF4). Here, we introduce the coupling of hollow-fiber flow field-flow fractionation (HF5) to multi-angle static light scattering (MALS) and differential refractometry (DRI) detection for the analysis of polysaccharides. In HF5, less stresses are placed on the macromolecules during separation than in SEC or HDC, and HF5 can offer a higher sensitivity, with less propensity for system overloading and analyte aggregation, than generally found in AF4. The coupling to MALS and DRI affords the determination of absolute, calibration-curve-independent molar mass averages and dispersities. Results from the present HF5/MALS/DRI experiments with dextrans, pullulans, and larch arabinogalactan were augmented with hydrodynamic radius (RH) measurements from off-line quasi-elastic light scattering (QELS) and by RH distribution calculations and fractogram simulations obtained via a finite element analysis implementation of field-flow fractionation theory by commercially available software. As part of this study, we have investigated analyte recovery in HF5 and also possible reasons for discrepancies between calculated and simulated results vis-à-vis experimentally determined data. Published by Elsevier B.V.

  1. Analyzing the influence of PEG molecular weight on the separation of PEGylated gold nanoparticles by asymmetric-flow field-flow fractionation.

    PubMed

    Hansen, Matthew; Smith, Mackensie C; Crist, Rachael M; Clogston, Jeffrey D; McNeil, Scott E

    2015-11-01

    Polyethylene glycol (PEG) is an important tool for increasing the biocompatibility of nanoparticle therapeutics. Understanding how these potential nanomedicines will react after they have been introduced into the bloodstream is a critical component of the preclinical evaluation process. Hence, it is paramount that better methods for separating, characterizing, and analyzing these complex and polydisperse formulations are developed. We present a method for separating nominal 30-nm gold nanoparticles coated with various molecular weight PEG moieties that uses only phosphate-buffered saline as the mobile phase, without the need for stabilizing surfactants. The optimized asymmetric-flow field-flow fractionation technique using in-line multiangle light scattering, dynamic light scattering, refractive index, and UV-vis detectors allowed successful separation and detection of a mixture of nanoparticles coated with 2-, 5-, 10-, and 20-kDa PEG. The particles coated with the larger PEG species (10 and 20 kDa) were eluted at times significantly earlier than predicted by field-flow fractionation theory. This was attributed to a lower-density PEG shell for the higher molecular weight PEGylated nanoparticles, which allows a more fluid PEG surface that can be greater influenced by external forces. Hence, the apparent particle hydrodynamic size may fluctuate significantly depending on the overall density of the stabilizing surface coating when an external force is applied. This has considerable implications for PEGylated nanoparticles intended for in vivo application, as nanoparticle size is important for determining circulation times, accumulation sites, and routes of excretion, and highlights the importance and value of the use of secondary size detectors when one is working with complex samples in asymmetric-flow field-flow fractionation.

  2. Chemical speciation studies on DU contaminated soils using flow field flow fractionation linked to inductively coupled plasma mass spectrometry (FlFFF-ICP-MS).

    PubMed

    Brittain, S R; Cox, A G; Tomos, A D; Paterson, E; Siripinyanond, A; McLeod, C W

    2012-03-01

    Flow field flow fractionation (FlFFF) in combination with inductively coupled plasma mass spectrometry (ICP-MS) was used to study the chemical speciation of U and trace metals in depleted uranium (DU) contaminated soils. A chemical extraction procedure using sodium pyrophosphate, followed by isolation of humic and fulvic substances was applied to two dissimilar DU contaminated sample types (a sandy soil and a clay-rich soil), in addition to a control soil. The sodium pyrophosphate fractions of the firing range soils (Eskmeals and Kirkcudbright) were found to contain over 50% of the total U (measured after aqua regia digestion), compared to approximately 10% for the control soil. This implies that the soils from the contaminated sites contained a large proportion of the U within more easily mobile soil fractions. Humic and fulvic acid fractions each gave characteristic peak maxima for analytes of interest (Mn, Fe, Cu, Zn, Pb and U), with the fulvic acid fraction eluting at a smaller diameter (approximately 2.1 nm on average) than the humic fraction (approximately 2.4 nm on average). DU in the fulvic acid fraction gave a bimodal peak, not apparent for other trace elements investigated, including natural U. This implies that DU interacts with the fulvic acid fraction in a different way to all other elements studied.

  3. Size-based speciation of iron in clay mineral particles by gravitational field-flow fractionation with electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Chantiwas, Rattikan; Beckett, Ronald; Grudpan, Kate

    2005-01-01

    Gravitational field-flow fractionation (FFF) coupled to UV and ETAAS detectors has been tested for micron-size particles in the range of 5-20 μm using three Fe-rich clay samples. The iron content estimated after aqua regia extraction was about 20-40 mg kg -1. The ETAAS analysis was performed both off-line from collected fractions and in an online continuous sampling mode using a specially designed flow through vial placed in the autosampler of the ETAAS. Comparison of the direct injection method with total analysis after aqua regia digestion shows that slurry injection of the dilute samples in the gravitational field-flow fractionation (GrFFF) effluent is quite efficient in these samples. In the majority of cases, more than 90% recovery was obtained for the slurry injection method. Fe mass-based particle size distributions and Fe concentration versus particle diameter plots can be generated using certain assumptions. This provides detailed information on size-based speciation of particulate samples. Generally, the Fe concentrations in the particles decreased slightly with an increase in particle size as is often found for soil and sediment samples.

  4. Different elution modes and field programming in gravitational field-flow fractionation. IV. Field programming achieved with channels of non-constant cross-sections.

    PubMed

    Plocková, Jana; Matulík, Frantisek; Chmelík, Josef

    2002-04-26

    Force field programming provided increased speed of separation with an improved resolution and detection capability in many field-flow fractionation (FFF) techniques. Gravitational field-flow fractionation (GFFF) uses the Earth's gravitational field to cause the settlement of particles towards the channel accumulation wall. Although this field is constant and relatively weak, there are different ways to implement force field programming in GFFF. Because hydrodynamic lift forces (HLF) participate in the separation process in focusing (hyperlayer) elution mode, they can control the resulting force field acting on particles via changes in flow-velocity. These changes can be accomplished by a programmable pump or with channels of non-constant cross-sections. This work is focused on flow-velocity programming accomplished with channels of non-constant cross-sections. Three trapezoidal channels of decreasing breadth and two channels of decreasing height (along the longitudinal axis) are tested as tools for optimization of the separation of a model silica gel particle mixture. The trapezoidal channels yielded reduced separation times. However, taking into account both speed of separation and resolution, the optimization effect was lower compared with the flow-rate gradients generated by a programmable pump. The channels of non-constant height did not yield advantageous separations.

  5. Interface for direct and continuous sample-matrix deposition onto a MALDI probe for polymer analysis by thermal field flow fractionation and off-line MALDI-MS.

    PubMed

    Basile, Franco; Kassalainen, Galina E; Ratanathanawongs Williams, S Kim

    2005-05-01

    A simple interface based on an oscillating capillary nebulizer (OCN) is described for direct deposition of eluate from a thermal field-flow fractionation (ThFFF) system onto a matrix-assisted laser desorption/ionization (MALDI) probe. In this study, the polymer-containing eluent from the ThFFF system was mixed on-line with MALDI matrix solution and deposited directly onto a moving MALDI probe. The result was a continuous sample track representative of the fractionation process. Subsequent off-line MALDI-mass spectrometry analysis was performed in automated and manual modes. Polystyrene samples of broad polydispersity were used to characterize the overall system performance. The OCN interface is easy to build and operate without the use of heaters or high voltages and is compatible with any MALDI probe format.

  6. Size characterization of barley starch granules by gravitational field-flow fractionation: a rapid, low-cost method to assess the brewing capability of different strains.

    PubMed

    Reschiglian, Pierluigi; Zattoni, Andrea; Casolari, Sonia; Krumlova, Andrea; Budinska, Marcela; Chmelík, Josef

    2002-04-01

    Cereal starch occurs as two types of micrometer-sized granules, large and small. Large starch granules are more susceptible to enzymatic hydrolysis. When cereal starch is used for fermentation processes, as in brewing of barley malt, the barley strains with the highest content of large starch granules should be preferred. Gravitational field-flow fractionation (GFFF) is a separation method able to fractionate starch samples at low cost and short analysis time. In this work, the search for the best GFFF conditions for the analytical separation of barley starch within an inter-laboratory approach is presented. For different barley strains cultivated under monitored conditions the size distributions of starch granules is here quickly monitored and characterized by GFFF. As a consequence, dimensional characterization of barley starch can allow for the selection of the most suitable strains with the lowest content of non-degradable starch.

  7. Top-down and bottom-up lipidomic analysis of rabbit lipoproteins under different metabolic conditions using flow field-flow fractionation, nanoflow liquid chromatography and mass spectrometry.

    PubMed

    Byeon, Seul Kee; Kim, Jin Yong; Lee, Ju Yong; Chung, Bong Chul; Seo, Hong Seog; Moon, Myeong Hee

    2015-07-31

    This study demonstrated the performances of top-down and bottom-up approaches in lipidomic analysis of lipoproteins from rabbits raised under different metabolic conditions: healthy controls, carrageenan-induced inflammation, dehydration, high cholesterol (HC) diet, and highest cholesterol diet with inflammation (HCI). In the bottom-up approach, the high density lipoproteins (HDL) and the low density lipoproteins (LDL) were size-sorted and collected on a semi-preparative scale using a multiplexed hollow fiber flow field-flow fractionation (MxHF5), followed by nanoflow liquid chromatography-ESI-MS/MS (nLC-ESI-MS/MS) analysis of the lipids extracted from each lipoprotein fraction. In the top-down method, size-fractionated lipoproteins were directly infused to MS for quantitative analysis of targeted lipids using chip-type asymmetrical flow field-flow fractionation-electrospray ionization-tandem mass spectrometry (cAF4-ESI-MS/MS) in selected reaction monitoring (SRM) mode. The comprehensive bottom-up analysis yielded 122 and 104 lipids from HDL and LDL, respectively. Rabbits within the HC and HCI groups had lipid patterns that contrasted most substantially from those of controls, suggesting that HC diet significantly alters the lipid composition of lipoproteins. Among the identified lipids, 20 lipid species that exhibited large differences (>10-fold) were selected as targets for the top-down quantitative analysis in order to compare the results with those from the bottom-up method. Statistical comparison of the results from the two methods revealed that the results were not significantly different for most of the selected species, except for those species with only small differences in concentration between groups. The current study demonstrated that top-down lipid analysis using cAF4-ESI-MS/MS is a powerful high-speed analytical platform for targeted lipidomic analysis that does not require the extraction of lipids from blood samples. Copyright © 2015 Elsevier B

  8. Enzymatic determination of cholesterol and triglycerides in serum lipoprotein profiles by asymmetrical flow field-flow fractionation with on-line, dual detection.

    PubMed

    Rambaldi, Diana Cristina; Reschiglian, Pierluigi; Zattoni, Andrea; Johann, Christoph

    2009-11-03

    Alterations of lipoproteins (LPs) and related lipid levels in blood serum are correlated to the risk of coronary artery disease (CAD). Fast, possibly automated methods to obtain complete, multi-parametric LP profiles are therefore welcome to be developed for routine, clinical analysis practice. In this work, asymmetrical flow field-flow fractionation (AF4) with on-line, dual post-fractionation reaction detection (PFRD) is applied to develop a method for single-run, simultaneous quantification of cholesterol (CHOL) and triglycerides (TGs) in each fractionated LP class. The enzymatic reagents used for the post-fractionation reaction are available as commercial kits for certified, standard clinical protocols for the analysis of CHOL and TGs in serum. Using CHOL and glycerol as reference standards, a new procedure is applied to optimize the experimental conditions for PFRD-based, quantitative analysis. Upon optimized PFRD and AF4 conditions, results obtained for the determination of total CHOL (TC), TGs, HDL-cholesterol (HDL-C), and LDL-cholesterol (LDL-C) in a set of serum samples from healthy donors are found in agreement with the values provided by a clinical laboratory. The intra-day and inter-day precisions of the method were found always lower than 10% (CV). When the method was applied to serum samples from patients affected by sepsis, differences in CHOL and TG profiles between patients and healthy donors were observed.

  9. Effect of varying flow regimes upon elution behaviour, apparent molecular characteristics and hydrodynamic properties of amylopectin isolated from normal corn starch using asymmetrical flow field-flow fractionation.

    PubMed

    Juna, Shazia; Huber, Anton

    2012-01-06

    A detailed study of the elution behaviour, apparent molecular characteristics and hydrodynamic properties of amylopectin-type fraction (isolated from normal corn starch) in aqueous media employing asymmetrical flow field-flow fractionation (AF4) was undertaken by systematically varying the channel flow (F(ch)), cross flow (F(cr)) and F(cr)/F(ch) ratios. Distributions of apparent molar masses and radii of gyration, mass recoveries and hydrodynamic radii decreased as a function of increasing F(cr) at a fixed F(ch), due to the increase in the retention of amylopectin-type fraction in the AF4 channel. Increased retention of the amylopectin-type fraction in the AF4 channel was also observed at low F(ch) and high F(cr)/F(ch) ratios. Large amylopectin-type molecules/particles (possibly aggregates) eluted at high F(ch), low F(cr) and low F(cr)/F(ch) ratios. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. A new analytical approach based on asymmetrical flow field-flow fractionation coupled to ultraviolet spectrometry and light scattering detection for SWCNT aqueous dispersion studies.

    PubMed

    Gigault, Julien; Grassl, Bruno; Lespes, Gaëtane

    2012-02-21

    This work demonstrates the potential of asymmetrical flow field-flow fractionation (A4F) coupled to Ultraviolet spectrometry (UV) and multi-angle light scattering (MALS) for the study of single-walled carbon nanotube (SWCNT) dispersion in aqueous solutions containing a surfactant. The results indicate that this technique is a powerful analytical tool that is able to evaluate SWCNT dispersion states in aqueous media and, more importantly, determine the presence or absence of aggregates, the numbers and sizes of different SWCNT populations and the SWCNT size distribution. Dynamic light scattering was employed to complete and demonstrate the relevance of the data that were obtained via A4F-UV-MALS. Two different anionic surfactants that are used to disperse SWCNTs were then studied. The dispersing powers of the surfactants were experimentally evaluated based on their structural organizations. This study demonstrates that surfactant concentration and sonication energy are key parameters that control the SWCNT dispersion state and SWCNT structural integrity therein.

  11. Co-elution effects can influence molar mass determination of large macromolecules with asymmetric flow field-flow fractionation coupled to multiangle light scattering.

    PubMed

    Perez-Rea, Daysi; Zielke, Claudia; Nilsson, Lars

    2017-07-14

    Starch and hence, amylopectin is an important biomacromolecule in both the human diet as well as in technical applications. Therefore, accurate and reliable analytical methods for its characterization are needed. A suitable method for analyzing macromolecules with ultra-high molar mass, branched structure and high polydispersity is asymmetric flow field-flow fractionation (AF4) in combination with multiangle light scattering (MALS) detection. In this paper we illustrate how co-elution of low quantities of very large analytes in AF4 may cause disturbances in the MALS data which, in turn, causes an overestimation of the size. Furthermore, it is shown how pre-injection filtering of the sample can improve the results. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Size determination and quantification of engineered cerium oxide nanoparticles by flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry.

    PubMed

    Sánchez-García, L; Bolea, E; Laborda, F; Cubel, C; Ferrer, P; Gianolio, D; da Silva, I; Castillo, J R

    2016-03-18

    Facing the lack of studies on characterization and quantification of cerium oxide nanoparticles (CeO2 NPs), whose consumption and release is greatly increasing, this work proposes a method for their sizing and quantification by Flow Field-flow Fractionation (FFFF) coupled to Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Two modalities of FFFF (Asymmetric Flow- and Hollow Fiber-Flow Field Flow Fractionation, AF4 and HF5, respectively) are compared, and their advantages and limitations discussed. Experimental conditions (carrier composition, pH, ionic strength, crossflow and carrier flow rates) are studied in detail in terms of NP separation, recovery, and repeatability. Size characterization of CeO2 NPs was addressed by different approaches. In the absence of feasible size standards of CeO2 NPs, suspensions of Ag, Au, and SiO2 NPs of known size were investigated. Ag and Au NPs failed to show a comparable behavior to that of the CeO2 NPs, whereas the use of SiO2 NPs provided size estimations in agreement to those predicted by the theory. The latter approach was thus used for characterizing the size of CeO2 NPs in a commercial suspension. Results were in adequate concordance with those achieved by transmission electron microscopy, X-ray diffraction and dynamic light scattering. The quantification of CeO2 NPs in the commercial suspension by AF4-ICP-MS required the use of a CeO2 NPs standards, since the use of ionic cerium resulted in low recoveries (99 ± 9% vs. 73 ± 7%, respectively). A limit of detection of 0.9 μg L(-1) CeO2 corresponding to a number concentration of 1.8 × 1012 L(-1) for NPs of 5 nm was achieved for an injection volume of 100 μL.

  13. Characterization of oxidized tannins: comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering.

    PubMed

    Vernhet, Aude; Dubascoux, Stéphane; Cabane, Bernard; Fulcrand, Hélène; Dubreucq, Eric; Poncet-Legrand, Céline

    2011-09-01

    Condensed tannins are a major class of plant polyphenols. They play an important part in the colour and taste of foods and beverages. Due to their chemical reactivity, tannins are not stable once extracted from plants. A number of chemical reactions can take place, leading to structural changes of the native structures to give so-called derived tannins and pigments. This paper compares results obtained on native and oxidized tannins with different techniques: depolymerization followed by high-performance liquid chromatography analysis, small-angle X-ray scattering (SAXS) and asymmetric flow field-flow fractionation (AF4). Upon oxidation, new macromolecules were formed. Thioglycolysis experiments showed no evidence of molecular weight increase, but thioglycolysis yields drastically decreased. When oxidation was performed at high concentration (e.g., 10 g L(-1)), the weight average degree of polymerization determined from SAXS increased, whereas it remained stable when oxidation was done at low concentration (0.1 g L(-1)), indicating that the reaction was intramolecular, yet the conformations were different. Differences in terms of solubility were observed; ethanol being a better solvent than water. We also separated soluble and non-water-soluble species of a much oxidized fraction. Thioglycolysis showed no big differences between the two fractions, whereas SAXS and AF4 showed that insoluble macromolecules have a weight average molecular weight ten times higher than the soluble ones.

  14. Flow field-flow fractionation for the analysis and characterization of natural colloids and manufactured nanoparticles in environmental systems: a critical review.

    PubMed

    Baalousha, M; Stolpe, B; Lead, J R

    2011-07-08

    The use of flow field flow fractionation (FlFFF) for the separation and characterization of natural colloids and nanoparticles has increased in the last few decades. More recently, it has become a popular method for the characterization of manufactured nanoparticles. Unlike conventional filtration methods, FlFFF provides a continuous and high-resolution separation of nanoparticles as a function of their diffusion coefficient, hence the interest for use in determining particle size distribution. Moreover, when coupled to other detectors such as inductively coupled plasma-mass spectroscopy, light scattering, UV-absorbance, fluorescence, transmission electron microscopy, and atomic force microscopy, FlFFF provides a wealth of information on particle properties including, size, shape, structural parameters, chemical composition and particle-contaminant association. This paper will critically review the application of FlFFF for the characterization of natural colloids and natural and manufactured nanoparticles. Emphasis will be given to the detection systems that can be used to characterize the nanoparticles eluted from the FlFFF system, the obtained information and advantages and limitation of FlFFF compared to other fractionation and particle sizing techniques. This review will help users understand (i) the theoretical principles and experimental consideration of the FlFFF, (ii) the range of analytical tools that can be used to further characterize the nanoparticles after fractionation by FlFFF, (iii) how FlFFF results are compared to other analytical techniques and (iv) the range of applications of FlFFF for natural and manufactured NPs.

  15. TiO2 in commercial sunscreen lotion: flow field-flow fractionation and ICP-AES together for size analysis.

    PubMed

    Contado, Catia; Pagnoni, Antonella

    2008-10-01

    A new method for determining the size of titanium dioxide particles is proposed and assayed in a commercial sunscreen product. Today many sun protection cosmetics incorporate physical UV filters as active ingredients, and there are no official methods for determining these compounds in sunscreen cosmetics. Here flow field-flow fractionation (FlFFF) has been tested, first to sort two different types of TiO2 nano- and microstandard materials (AeroxideTiO2 Degussa P-25 and TiO2 rutile 0.1-0.2-microm size) and then to fractionate TiO2 particles, extracted from a commercial sunscreen lotion. All the TiO2 FlFFF separations were detected by UV but during elution fractions were collected and their Ti content measured by inductively coupled plasma-atomic emission spectrometer (ICP-AES); the Ti concentration profiles obtained by ICP-AES were well correlated with the UV signals. The TiO2 particle mass-size distribution were calculated from the UV profiles. This methodology is relatively simple and rapid, and the sample treatment is as a whole easy and low cost.

  16. Characterization of colloidal arsenic at two abandoned gold mine sites in Nova Scotia, Canada, using asymmetric flow-field flow fractionation-inductively coupled plasma mass spectrometry.

    PubMed

    Tindale, Kathryn J; Patel, Pritesh J; Wallschläger, Dirk

    2016-11-01

    Asymmetric flow-field flow fractionation-inductively-coupled plasma-mass spectrometry was used to determine whether colloidal arsenic (As) exists in soil pore water and soil extract samples at two arsenic-contaminated abandoned gold mines (Montague and Goldenville, Nova Scotia). Colloidal arsenic was found in 12 out of the 80 collected samples (=15%), and was primarily associated with iron (Fe) in the encountered colloids. The molar Fe/As ratios indicate that the colloids in some samples appeared to be discrete iron-arsenic minerals, whereas in other samples, they were more consistent with As-rich iron (oxy)hydroxides. Up to three discrete size fractions of colloidal As were encountered in the samples, with mean colloid diameters between 6 and 14nm. The pore water samples only contained one size fraction of As-bearing colloids (around 6nm diameter), while larger As-bearing colloids were only encountered in soil extracts. Copyright © 2016. Published by Elsevier B.V.

  17. The potential of asymmetric flow field-flow fractionation hyphenated to multiple detectors for the quantification and size estimation of silica nanoparticles in a food matrix.

    PubMed

    Heroult, Julien; Nischwitz, Volker; Bartczak, Dorota; Goenaga-Infante, Heidi

    2014-06-01

    This work represents a first systematic approach to the size-based elemental quantification and size estimation of metal(loid) oxide nanoparticles such as silica (SiO2) in a real food matrix using asymmetric flow field-flow fractionation coupled online with inductively coupled plasma mass spectrometry (ICP-MS) and multi-angle light scattering (MALS) and offline with transmission electron microscopy (TEM) with energy-dispersive X-ray analysis (EDAX). Coffee creamer was selected as the model sample since it is known to contain silica as well as metal oxides such as titania at the milligramme per kilogramme levels. Optimisation of sample preparation conditions such as matrix-to-solvent ratio, defatting with organic solvents and sonication time that may affect nanoparticle size and size distribution in suspensions was investigated. Special attention was paid to the selection of conditions that minimise particle transformation during sample preparation and analysis. The coffee creamer matrix components were found to stabilise food grade SiO2 particles in comparison with water suspensions whilst no significant effect of defatting using hexane was found. The use of sample preparation procedures that mimic food cooking in real life was also investigated regarding their effect on particle size and particle size distribution of silica nanoparticles in the investigated food matrix; no significant effect of the water temperature ranging from ambient temperature to 60 °C was observed. Field-flow fractionation coupled to inductively coupled plasma-mass spectrometry (FFF-ICP-MS) analysis of extracts of both unspiked coffee creamer and coffee creamer spiked with food grade silicon dioxide, using different approaches for size estimation, enabled determination of SiO2 size-based speciation. Element-specific detection by ICP-MS and post-FFF calibration with elemental calibration standards was used to determine the elemental composition of size fractions separated online by FFF

  18. Size Dependent Lipidomic Analysis of Urinary Exosomes from Patients with Prostate Cancer by Flow Field-Flow Fractionation and Nanoflow Liquid Chromatography-Tandem Mass Spectrometry.

    PubMed

    Yang, Joon Seon; Lee, Jong Cheol; Byeon, Seul Kee; Rha, Koon Ho; Moon, Myeong Hee

    2017-02-21

    Exosomes are membrane-bound extracellular vesicles involved in intercellular communication and tumor cell metastasis. In this study, flow field-flow fractionation (FlFFF) was utilized to separate urinary exosomes by size, demonstrating a significant difference in exosome sizes between healthy controls and patients with prostate cancer (PCa). Exosome fractions of different sizes were collected for microscopic analysis during an FlFFF run and evaluated with exosome marker proteins using Western blot analysis. The results indicated that exosomes of different sizes originated from different types of cells. Collected exosome fractions were further examined using nanoflow ultrahigh performance liquid chromatography-electrospray ionization-tandem mass spectrometry (nUPLC-ESI-MS/MS) for lipidomic analysis. A total of 162 lipids (from 286 identified) were quantified using a selected reaction monitoring (SRM) method. The overall amount of lipids increased by 1.5- to 2-fold in patients with PCa and degree of increase was more significant in the smaller fractions (diameter <150 nm) than in the larger ones (diameter >150 nm) some classes of lipids. In addition, neutral lipids like diacylglycerol (DAG) and triacylglycerol (TAG) decreased in all exosomes without size dependency. Moreover, a dramatic increase in 22:6/22:6-phosphatidylglycerol (PG) was observed and significant decrease in (16:0,16:0)- and (16:1, 18:1)-DAG species (nearly 5-fold) and high abundant TAG species (>2.5-fold) was observed in patients with PCa. The results of this study indicate that FlFFF can be employed for the high-speed screening of urinary exosome sizes in patients with PCa and lipidomic analysis of the fractionated exosomes has potential for developing and distinguishing biomarkers of PCa.

  19. Dielectrophoretic columnar focusing device

    DOEpatents

    James, Conrad D.; Galambos, Paul C.; Derzon, Mark S.

    2010-05-11

    A dielectrophoretic columnar focusing device uses interdigitated microelectrodes to provide a spatially non-uniform electric field in a fluid that generates a dipole within particles in the fluid. The electric field causes the particles to either be attracted to or repelled from regions where the electric field gradient is large, depending on whether the particles are more or less polarizable than the fluid. The particles can thereby be forced into well defined stable paths along the interdigitated microelectrodes. The device can be used for flow cytometry, particle control, and other process applications, including cell counting or other types of particle counting, and for separations in material control.

  20. Colloidal mercury (Hg) distribution in soil samples by sedimentation field-flow fractionation coupled to mercury cold vapour generation atomic absorption spectroscopy.

    PubMed

    Santoro, A; Terzano, R; Medici, L; Beciani, M; Pagnoni, A; Blo, G

    2012-01-01

    Diverse analytical techniques are available to determine the particle size distribution of potentially toxic elements in matrices of environmental interest such as soil, sediments, freshwater and groundwater. However, a single technique is often not exhaustive enough to determine both particle size distribution and element concentration. In the present work, the investigation of mercury in soil samples collected from a polluted industrial site was performed by using a new analytical approach which makes use of sedimentation field-flow fractionation (SdFFF) coupled to cold vapour generation electrothermal atomic absorption spectroscopy (CV-ETAAS). The Hg concentration in the SdFFF fractions revealed a broad distribution from about 0.1 to 1 μm, roughly following the particle size distributions, presenting a maximum at about 400-700 nm in diameter. A correlation between the concentration of Hg in the colloidal fraction and organic matter (O.M.) content in the soil samples was also found. However, this correlation is less likely to be related to Hg sorption to soil O.M. but rather to the presence of colloidal mercuric sulfide particles whose size is probably controlled by the occurrence of dissolved O.M. The presence of O.M. could have prevented the aggregation of smaller particles, leading to an accumulation of mercuric sulfides in the colloidal fraction. In this respect, particle size distribution of soil samples can help to understand the role played by colloidal particles in mobilising mercury (also as insoluble compounds) and provide a significant contribution in determining the environmental impact of this toxic element.

  1. Determination of cholesterol and triglycerides in serum lipoproteins using flow field-flow fractionation coupled to gas chromatography-mass spectrometry.

    PubMed

    Qureshi, Rashid Nazir; Kaal, Erwin; Janssen, Hans-Gerd; Schoenmakers, Peter J; Kok, Wim Th

    2011-11-14

    Asymmetric flow field flow fractionation (AsFlFFF) was combined with pyrolysis-gas chromatography mass spectrometry for a sized based fractionation and a detailed compositional study of the triglycerides and cholesterol associated with the various lipoprotein subclasses present in human serum. Serum samples were injected in the AsFlFFF instrument and fractionated with a time-delayed exponential decay cross flow program. The fractions collected after AsFlFFF elution were injected into a programmable temperature vaporizer (PTV) GC-injector, containing a fritted liner. A temperature and split-flow program for the PTV injector was optimized for the thermally assisted hydrolysis and methylation of the compounds of interest. The resulting fatty acid and cholesterol methyl esters were separated by GC and characteristic fragment ions were detected by MS. The system was optimized and calibrated with triglyceride and cholesterol standards for quantitative analysis. The possible interference by phospholipids with the quantitative results was investigated and found to be of minor importance. The concentrations and lipoprotein profiles of triglycerides and cholesterol were determined in a pooled serum sample of healthy volunteers and a serum sample of a sepsis patient. The results obtained with the GC-MS approach were compared with those of a previously developed method based on AsFlFFF with a dual enzymatic reaction detection system. A good agreement of the profiles was found, for cholesterol as well as for the triglycerides, even when the GC-MS method quantifies the fatty acids while with the enzymatic reaction method the glycerol concentrations are determined. Total cholesterol and triglyceride concentration values for the serum samples showed good agreement with the results of the standard enzymatic method as used in practice in the university hospital. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. High speed two-dimensional protein separation without gel by isoelectric focusing-asymmetrical flow field flow fractionation: application to urinary proteome.

    PubMed

    Kim, Ki Hun; Moon, Myeong Hee

    2009-09-01

    An online multilane channel system for isoelectric focusing and asymmetrical flow field-flow fractionation (IEF-AF4) is utilized for the two-dimensional separation (2D: isoelectric point, pI, and hydrodynamic diameter, d(s)) of a human proteome sample followed by the shotgun proteomic analysis using nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS-MS). IEF-AF4 was recently developed to carry out nongel-based high speed two-dimensional protein separation [ Kim , K. , et al. Anal. Chem. 2009, 81 , 1715 ]. In IEF-AF4, proteins are separated according to pI along an IEF channel located at the head of six AF4 channels, and then the fractionated protein bands are directed to multilane AF4 channels for size-based separation. In this report, the original IEF-AF4 system has been modified to avoid the possible adsorption of proteins onto the membrane wall of IEF segments during isoelectric focusing by isolating the IEF channel segments from the multilane AF4 channels. The performance of the modified IEF-AF4 system was tested with protein standards and was further applied for the 2D fractionation of the human urinary proteome sample under two ampholyte solutions with different pH ranges (pH 3-10 and 3-6). The entire 2D separation was achieved in less than 30 min. The collected protein fractions were digested for peptide analysis using nLC-ESI-MS-MS, resulting in the identification of 245 total urinary proteins, including 110 unique proteins that are not yet reported in literature. Our experiments also showed a higher efficiency in the identification of urine proteins using ampholyte solution in the narrower pH range.

  3. Combining asymmetrical flow field-flow fractionation with on- and off-line fluorescence detection to examine biodegradation of riverine dissolved and particulate organic matter.

    PubMed

    Lee, Sang Tak; Yang, Boram; Kim, Jin-Yong; Park, Ji-Hyung; Moon, Myeong Hee

    2015-08-28

    This study demonstrated that asymmetrical flow field-flow fractionation (AF4) coupled with on-line UV and fluorescence detection (FLD) and off-line excitation-emission matrix (EEM) fluorescence spectroscopy can be employed to analyze the influence of microbial metabolic activity on the consumption and production of freshwater organic matter. With the AF4 system, organic matter is on-line enriched during a focusing/relaxation period, which is an essential process prior to separation. Size-fractionated chromophoric and fluorophoric organic materials were simultaneously monitored during the 30-min AF4 separation process. Two fractions of different sizes (dissolved organic matter (DOM) and particulate organic matter (POM)) of freshwater samples from three locations (up-, mid-, and downstream) along the Han River basin of Korea were incubated with the same inoculum for 14 days to analyze fraction-specific alterations in optical properties using AF4-UV-FLD. A comparison of AF4 fractograms obtained from pre- and post-incubation samples revealed that POM-derived DOM were more susceptible to microbial metabolic activity than was DOM. Preferential microbial consumption of protein-like DOM components concurred with enhanced peaks of chromophoric and humic-like fluorescent components, presumably formed as by-products of microbial processing. AF4-UV-FLD combined with off-line identification of microbially processed components using EEM fluorescence spectroscopy provides a powerful tool to study the relationship between microbial activity and composition as well as biodegradability of DOM and POM-derived DOM from different origins, especially for the analysis of chromophoric and fluorophoric organic matter that are consumed and produced by microbial metabolic activity. The proposed AF4 system can be applied to organic matter in freshwater samples having low concentration range (0.3-2.5ppm of total organic carbon) without a pre-concentration procedure.

  4. Importance of material matching in the calibration of asymmetric flow field-flow fractionation: material specificity and nanoparticle surface coating effects on retention time

    NASA Astrophysics Data System (ADS)

    Qu, Haiou; Quevedo, Ivan R.; Linder, Sean W.; Fong, Andrew; Mudalige, Thilak K.

    2016-10-01

    Asymmetric flow field-flow fractionation (AF4) coupled with dynamic light scattering or multiangle light scattering detectors is a promising technique for the size-based separation of colloidal particles (nano- and submicron scale) and the online determination of the particle size of the separated fractions in aqueous suspensions. In most cases, the applications of these detectors are problematic due to the material-specific properties of the analyte that results in erroneous calculations, and as an alternative, different nanoparticle size standards are required to properly calibrate the size-based retention in AF4. The availability of nanoparticle size standards in different materials is limited, and this deviation from ideal conditions of retention is mainly due to material-specific and particle coating-specific membrane-particle interactions. Here, we present an experimental method on the applicability of polystyrene nanoparticles (PS NP) as standard for AF4 calibration and compare with gold nanoparticle (Au NP) standards having different nominal sizes and surface functionalities.

  5. Coupling asymmetric flow-field flow fractionation and fluorescence parallel factor analysis reveals stratification of dissolved organic matter in a drinking water reservoir.

    PubMed

    Pifer, Ashley D; Miskin, Daniel R; Cousins, Sarah L; Fairey, Julian L

    2011-07-08

    Using asymmetrical flow field-flow fractionation (AF4) and fluorescence parallel factor analysis (PARAFAC), we showed physicochemical properties of chromophoric dissolved organic matter (CDOM) in the Beaver Lake Reservoir (Lowell, AR) were stratified by depth. Sampling was performed at a drinking water intake structure from May to July 2010 at three depths (3-, 10-, and 18-m) below the water surface. AF4-fractograms showed that the CDOM had diffusion coefficient peak maximums between 3.5 and 2.8 x 10⁻⁶ cm² s⁻¹, which corresponded to a molecular weight range of 680-1950 Da and a size of 1.6-2.5 nm. Fluorescence excitation-emission matrices of whole water samples and AF4-generated fractions were decomposed with a PARAFAC model into five principal components. For the whole water samples, the average total maximum fluorescence was highest for the 10-m depth samples and lowest (about 40% less) for 18-m depth samples. While humic-like fluorophores comprised the majority of the total fluorescence at each depth, a protein-like fluorophore was in the least abundance at the 10-m depth, indicating stratification of both total fluorescence and the type of fluorophores. The results present a powerful approach to investigate CDOM properties and can be extended to investigate CDOM reactivity, with particular applications in areas such as disinfection byproduct formation and control and evaluating changes in drinking water source quality driven by climate change.

  6. A quantitative determination of magnetic nanoparticle separation using on-off field operation of quadrupole magnetic field-flow fractionation (QMgFFF).

    PubMed

    Orita, Toru; Moore, Lee R; Joshi, Powrnima; Tomita, Masahiro; Horiuchi, Takashi; Zborowski, Maciej

    2013-01-01

    Quadrupole Magnetic Field-Flow Fractionation (QMgFFF) is a technique for characterization of sub-micrometer magnetic particles based on their retention in the magnetic field from flowing suspensions. Different magnetic field strengths and volumetric flow rates were tested using on-off field application and two commercial nanoparticle preparations that significantly differed in their retention parameter, λ (by nearly 8-fold). The fractograms showed a regular pattern of higher retention (98.6% v. 53.3%) for the larger particle (200 nm v. 90 nm) at the higher flow rate (0.05 mL/min v. 0.01 mL/min) at the highest magnetic field (0.52 T), as expected because of its lower retention parameter. The significance of this approach is a demonstration of a system that is simpler in operation than a programmed field QMgFFF in applications to particle mixtures consisting of two distinct particle fractions. This approach could be useful for detection of unwanted particulate contaminants, especially important in industrial and biomedical applications.

  7. A Quantitative Determination of Magnetic Nanoparticle Separation Using On-Off Field Operation of Quadrupole Magnetic Field-Flow Fractionation (QMgFFF)

    PubMed Central

    Orita, Toru; Moore, Lee R.; Joshi, Powrnima; Tomita, Masahiro; Horiuchi, Takashi; Zborowski, Maciej

    2014-01-01

    Quadrupole Magnetic Field-Flow Fractionation (QMgFFF) is a technique for characterization of sub-micrometer magnetic particles based on their retention in the magnetic field from flowing suspensions. Different magnetic field strengths and volumetric flow rates were tested using on-off field application and two commercial nanoparticle preparations that significantly differed in their retention parameter, λ (by nearly 8-fold). The fractograms showed a regular pattern of higher retention (98.6% v. 53.3%) for the larger particle (200 nm v. 90 nm) at the higher flow rate (0.05 mL/min v. 0.01 mL/min) at the highest magnetic field (0.52 T), as expected because of its lower retention parameter. The significance of this approach is a demonstration of a system that is simpler in operation than a programmed field QMgFFF in applications to particle mixtures consisting of two distinct particle fractions. This approach could be useful for detection of unwanted particulate contaminants, especially important in industrial and biomedical applications. PMID:23842422

  8. High-efficiency dielectrophoretic ratchet.

    PubMed

    Germs, Wijnand Chr; Roeling, Erik M; van Ijzendoorn, Leo J; Smalbrugge, Barry; de Vries, Tjibbe; Geluk, Erik Jan; Janssen, René A J; Kemerink, Martijn

    2012-10-01

    Brownian ratchets enable the use of thermal motion in performing useful work. They typically employ spatial asymmetry to rectify nondirected external forces that drive the system out of equilibrium (cf. running marbles on a shaking washboard). The major application foreseen for Brownian ratchets is high-selectivity fractionation of particle or molecule distributions. Here, we investigate the functioning of an important model system, the on/off ratchet for water-suspended particles, in which interdigitated finger electrodes can be switched on and off to create a time-dependent, spatially periodic but asymmetric potential. Surprisingly, we find that mainly dielectrophoretic rather than electrophoretic forces are responsible for the ratchet effect. This has major implications for the (a)symmetry of the ratchet potential and the settings needed for optimal performance. We demonstrate that by applying a potential offset the ratchet can be optimized such that its particle displacement efficiency reaches the theoretical upper limit corresponding to the electrode geometry and particle size. Efficient fractionation based on size selectivity is therefore not only possible for charged species, but also for uncharged ones, which greatly expands the applicability range of this type of Brownian ratchet.

  9. Asymmetrical Flow-Field-Flow Fractionation coupled with inductively coupled plasma mass spectrometry for the analysis of gold nanoparticles in the presence of natural nanoparticles.

    PubMed

    Meisterjahn, Boris; Neubauer, Elisabeth; Von der Kammer, Frank; Hennecke, Dieter; Hofmann, Thilo

    2014-11-03

    Flow-Field-Flow Fractionation (Flow-FFF), coupled with online detection systems, is one of the most promising tools available for the analysis and characterization of engineered nanoparticles (ENPs) in complex matrices. In order to demonstrate the applicability of Flow-FFF for the detection, quantification, and characterization of engineered gold nanoparticles (AuNPs), model dispersions were prepared containing AuNPs with diameters of 30 or 100nm, natural nanoparticles (NNPs) extracted from a soil sample, and different concentrations of natural organic matter (NOM), which were then used to investigate interactions between the AuNPs and the NNPs. It could be shown that light scattering detection can be used to evaluate the fractionation performance of the pure NNPs, but not the fractionation performance of the mixed samples that also contained AuNPs because of specific interactions between the AuNPs and the laser light. A combination of detectors (i.e. light absorbance and inductively coupled plasma mass spectrometry (ICP-MS)) was found to be useful for differentiating between heteroaggregation and homoaggregation of the nanoparticles (NPs). The addition of NOM to samples containing 30nm AuNPs stabilized the AuNPs without affecting the NP size distribution. However, fractograms for samples with no added NOM showed a change in the size distribution, suggesting interactions between the AuNPs and NNPs. This interpretation was supported by unchanged light absorption wavelengths for the AuNPs. In contrast, results for samples containing 100nm AuNPs were inconclusive with respect to recovery and size distributions because of problems with the separation system that probably related to the size and high density of these nanoparticles, highlighting the need for extensive method optimization strategies, even for nanoparticles of the same material but different sizes.

  10. Characterization of high molecular weight polyethylenes using high temperature asymmetrical flow field-flow fractionation with on-line infrared, light scattering, and viscometry detection.

    PubMed

    Mes, E P C; de Jonge, H; Klein, T; Welz, R R; Gillespie, D T

    2007-06-22

    High temperature asymmetrical flow field-flow fractionation (HTAF4) coupled to infrared (IR), multi-angle light scattering (MALS), and viscometry (Visc) detection is introduced as a tool for the characterization of high molecular weight polyethylenes. The high molecular weight fraction strongly affects the rheological behaviour and processability of polyethylene materials and can often not be accurately resolved by current technology such as high temperature size-exclusion chromatography (HTSEC). Molecular weight (M), radius of gyration (Rg), and intrinsic viscosity [eta] of linear high density polyethylene (HDPE) and branched low density polyethylene (LDPE) samples are studied in detail by HTAF4 and are compared to HTSEC. HTAF4 showed a better separation and mass recovery than HTSEC for very high molecular weight fractions in HDPE and LDPE samples. As no stationary phase is present in an HTAF4 channel, the technique does not show the typical drawbacks associated with HTSEC analysis of high molecular weight polyethylenes, such as, exclusion effects, shear degradation, and anomalous late elution of highly branched material. HTAF4 is applied to study the relation between the molecular weight and the zero shear viscosity eta0 for high molecular weight HDPE. It was found that the zero shear viscosity values predicted from HTAF4 results are in good qualitative agreement with measured values obtained from dynamic mechanical spectroscopy (DMS) experiments, whereas eta0 values predicted from HTSEC do not show a strong correlation. The low molecular weight cutoff of HTAF4 is approximately 5x10(4) as a result of relatively large pores in the HTAF4 channel membrane. HTAF4 is, therefore, currently not suited to analyze low molecular weight materials.

  11. Particle size characterization of titanium dioxide in sunscreen products using sedimentation field-flow fractionation-inductively coupled plasma-mass spectrometry.

    PubMed

    Samontha, Atitaya; Shiowatana, Juwadee; Siripinyanond, Atitaya

    2011-01-01

    Sedimentation field-flow fractionation-inductively coupled plasma-mass spectrometry (SdFFF-ICP-MS) was successfully applied to investigate particle size distribution of titanium dioxide (TiO(2)) in sunscreen samples after hexane extraction to remove organic components from the samples. Three brands of sunscreen products of various sun protection factor (SPF) value were used as samples. Different particle size distribution profiles were observed for sunscreen samples of various brands and SPF values; however, the particle size distributions of titanium dioxide in most sunscreen samples investigated in this work were larger than 100 nm. The titanium dioxide concentrations were higher for the products of higher SPF values. By comparing the results obtained from online SdFFF-ICP-MS and those from the off-line ICP-MS determination of titanium after acid digestion, ICP-MS was found to effectively atomize and ionize the titanium dioxide particle without the need for acid digestion of the samples. Therefore, the online coupling between SdFFF and ICP-MS could be effectively used to provide quantitative information of titanium dioxide concentrations across particle size distribution profiles.

  12. Combining gas-phase electrophoretic mobility molecular analysis (GEMMA), light scattering, field flow fractionation and cryo electron microscopy in a multidimensional approach to characterize liposomal carrier vesicles.

    PubMed

    Urey, Carlos; Weiss, Victor U; Gondikas, Andreas; von der Kammer, Frank; Hofmann, Thilo; Marchetti-Deschmann, Martina; Allmaier, Günter; Marko-Varga, György; Andersson, Roland

    2016-11-20

    For drug delivery, characterization of liposomes regarding size, particle number concentrations, occurrence of low-sized liposome artefacts and drug encapsulation are of importance to understand their pharmacodynamic properties. In our study, we aimed to demonstrate the applicability of nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyser (nES GEMMA) as a suitable technique for analyzing these parameters. We measured number-based particle concentrations, identified differences in size between nominally identical liposomal samples, and detected the presence of low-diameter material which yielded bimodal particle size distributions. Subsequently, we compared these findings to dynamic light scattering (DLS) data and results from light scattering experiments coupled to Asymmetric Flow-Field Flow Fractionation (AF4), the latter improving the detectability of smaller particles in polydisperse samples due to a size separation step prior detection. However, the bimodal size distribution could not be detected due to method inherent limitations. In contrast, cryo transmission electron microscopy corroborated nES GEMMA results. Hence, gas-phase electrophoresis proved to be a versatile tool for liposome characterization as it could analyze both vesicle size and size distribution. Finally, a correlation of nES GEMMA results with cell viability experiments was carried out to demonstrate the importance of liposome batch-to-batch control as low-sized sample components possibly impact cell viability. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  13. Biophysical characterization of influenza virus subpopulations using field flow fractionation and multiangle light scattering: correlation of particle counts, size distribution and infectivity.

    PubMed

    Wei, Ziping; McEvoy, Matt; Razinkov, Vladimir; Polozova, Alla; Li, Elizabeth; Casas-Finet, Jose; Tous, Guillermo I; Balu, Palani; Pan, Alfred A; Mehta, Harshvardhan; Schenerman, Mark A

    2007-09-01

    Adequate biophysical characterization of influenza virions is important for vaccine development. The influenza virus vaccines are produced from the allantoic fluid of developing chicken embryos. The process of viral replication produces a heterogeneous mixture of infectious and non-infectious viral particles with varying states of aggregation. The study of the relative distribution and behavior of different subpopulations and their inter-correlation can assist in the development of a robust process for a live virus vaccine. This report describes a field flow fractionation and multiangle light scattering (FFF-MALS) method optimized for the analysis of size distribution and total particle counts. The FFF-MALS method was compared with several other methods such as transmission electron microscopy (TEM), atomic force microscopy (AFM), size exclusion chromatography followed by MALS (SEC-MALS), quantitative reverse transcription polymerase chain reaction (RT Q-PCR), median tissue culture dose (TCID(50)), and the fluorescent focus assay (FFA). The correlation between the various methods for determining total particle counts, infectivity and size distribution is reported. The pros and cons of each of the analytical methods are discussed.

  14. Multidetector thermal field-flow fractionation as a unique tool for the tacticity-based separation of poly(methyl methacrylate)-polystyrene block copolymer micelles.

    PubMed

    Greyling, Guilaume; Pasch, Harald

    2015-10-02

    Poly(methyl methacrylate)-polystyrene (PMMA-PS) micelles with isotactic and syndiotactic coronas are prepared in acetonitrile and subjected to thermal field-flow fractionation (ThFFF) analysis at various conditions of increasing temperature gradients. It is shown for the first time that multidetector ThFFF provides comprehensive information on important micelle characteristics such as size (Dh), shape (Rg/Rh), aggregation number (Z), thermal diffusion (DT) and Soret coefficients (ST) as a function of temperature from a single injection. Moreover, it is found that micelles exhibit a unique decreasing trend in DT as a function of temperature which is independent of the tacticity of the corona and the micelle preparation method used. It is also demonstrated that ThFFF can monitor micelle to vesicle transitions as a function of temperature. In addition to ThFFF, it is found from DLS analysis that the tacticity of the corona influences the critical micelle concentration and the magnitude to which micelles expand/contract with temperature. The tacticity does not, however, influence the critical micelle temperature. Furthermore, the separation of micelles based on the tacticity of the corona highlight the unique capabilities of ThFFF.

  15. Agglomeration behaviour of titanium dioxide nanoparticles in river waters: A multi-method approach combining light scattering and field-flow fractionation techniques.

    PubMed

    Chekli, L; Roy, M; Tijing, L D; Donner, E; Lombi, E; Shon, H K

    2015-08-15

    Titanium dioxide nanoparticles (TiO2 NPs) are currently one of the most prolifically used nanomaterials, resulting in an increasing likelihood of release to the environment. This is of concern as the potential toxicity of TiO2 NPs has been investigated in several recent studies. Research into their fate and behaviour once entering the environment is urgently needed to support risk assessment and policy development. In this study, we used a multi-method approach combining light scattering and field-flow fractionation techniques to assess both the aggregation behaviour and aggregate structure of TiO2 NPs in different river waters. Results showed that both the aggregate size and surface-adsorbed dissolved organic matter (DOM) were strongly related to the initial DOM concentration of the tested waters (i.e. R(2) > 0.90) suggesting that aggregation of TiO2 NPs is controlled by the presence and concentration of DOM. The conformation of the formed aggregates was also found to be strongly related to the surface-adsorbed DOM (i.e. R(2) > 0.95) with increasing surface-adsorbed DOM leading to more compact structures. Finally, the concentration of TiO2 NPs remaining in the supernatant after sedimentation of the larger aggregates was found to decrease proportionally with both increasing IS and decreasing DOM concentration, resulting in more than 95% sedimentation in the highest IS sample.

  16. Gravitational field-flow fractionation integrated with chemiluminescence detection for a self-standing point-of-care compact device in bioanalysis.

    PubMed

    Casolari, S; Roda, B; Mirasoli, M; Zangheri, M; Patrono, D; Reschiglian, P; Roda, A

    2013-01-07

    A "Point-Of-Care-Testing" (POCT) system relies on portable and simply operated self-standing analytical devices. To fulfill diagnostic requirements, the POCT system should provide highly sensitive simultaneous detection of several biomarkers of the pathology of interest (multiplexing) in a short assay time. One of the main unsolved issues in POCT device development is the integration of pre-analytical sample preparation procedures in the miniaturized device. In this work, an integrated POCT system based on gravitational field-flow fractionation (GrFFF) and chemiluminescence (CL) detection is presented for the on-line sample pre-analytical treatment and/or clean-up and analysis of biological fluids. As a proof of principle for the new GrFFF-CL POCT system, the automatic on-line analysis of plasma alkaline phosphatase activity, a biomarker of obstructive liver diseases and bone disorders, starting from whole blood samples was developed. The GrFFF-CL POCT system was able to give quantitative results on blood samples from control and patients with low sample volume (0.5 μL) and reagent consumption, short analysis time (10 minutes), high reproducibility and with a linear range of 50-1400 IU L(-1). The system can be easily applied to on-line prepare plasma from whole blood for other clinical biomarkers and for other assay formats, based on immunoassay or DNA hybridization.

  17. Combining asymmetrical flow field-flow fractionation with light-scattering and inductively coupled plasma mass spectrometric detection for characterization of nanoclay used in biopolymer nanocomposites.

    PubMed

    Schmidt, B; Petersen, J H; Bender Koch, C; Plackett, D; Johansen, N R; Katiyar, V; Larsen, E H

    2009-12-01

    It is expected that biopolymers obtained from renewable resources will in due course become fully competitive with fossil fuel-derived plastics as food-packaging materials. In this context, biopolymer nanocomposites are a field of emerging interest since such materials can exhibit improved mechanical and barrier properties and be more suitable for a wider range of food-packaging applications. Natural or synthetic clay nanofillers are being investigated for this purpose in a project called NanoPack funded by the Danish Strategic Research Council. In order to detect and characterize the size of clay nanoparticulates, an analytical system combining asymmetrical flow field-flow fractionation (AF(4)) with multi-angle light-scattering detection (MALS) and inductively coupled plasma mass spectrometry (ICP-MS) is presented. In a migration study, we tested a biopolymer nanocomposite consisting of polylactide (PLA) with 5% Cloisite30B (a derivatized montmorillonite clay) as a filler. Based on AF(4)-MALS analyses, we found that particles ranging from 50 to 800 nm in radius indeed migrated into the 95% ethanol used as a food simulant. The full hyphenated AF(4)-MALS-ICP-MS system showed, however, that none of the characteristic clay minerals was detectable, and it is concluded that clay nanoparticles were absent in the migrate. Finally, by means of centrifugation experiments, a platelet aspect ratio of 320 was calculated for montmorillonite clay using AF(4)-MALS for platelet size measurements.

  18. Rejection of Commonly Used Electrolytes in Asymmetric Flow Field Flow Fractionation: Effects of Membrane Molecular Weight Cutoff Size, Fluid Dynamics, and Valence of Electrolytes.

    PubMed

    Mudalige, Thilak K; Qu, Haiou; Linder, Sean W

    2017-02-14

    Asymmetric flow field flow fractionation (AF4) is an efficient size-based separation technique for the characterization of submicron size particulates. In AF4, membranes having various molecular weight cutoff sizes are used as a barrier to retain particles while allowing the carrier fluid containing electrolytes to permeate. Here, we have hypothesized that electrolyte rejection by the barrier membrane leads to the accumulation of electrolytes in the channel during operation. Electrolyte accumulation can cause various adverse effects that can lead to membrane fouling. An instrument setup containing a conductivity detector was assembled, and the rejection of commonly used carrier electrolytes such as trisodium citrate, ethylenediaminetetraacetic acid, sodium chloride, and ammonium carbonate was evaluated by varying the concentration, cross-flow rate, focusing flow rate, membrane material type, and cutoff sizes. The results showed that electrolyte rejection increased with a decrease in the electrolyte concentration and the molecular weight cutoff size (pore size) or with an increase in the charge state of the anion in the carrier electrolytes. We proposed an electrostatic repulsion-based rejection mechanism and verified it with the measurement of the rejection rate while varying the electrolyte concentration in the running media.

  19. Investigations on the structure of solid lipid nanoparticles (SLN) and oil-loaded solid lipid nanoparticles by photon correlation spectroscopy, field-flow fractionation and transmission electron microscopy.

    PubMed

    Jores, Katja; Mehnert, Wolfgang; Drechsler, Markus; Bunjes, Heike; Johann, Christoph; Mäder, Karsten

    2004-03-05

    Recently, colloidal dispersions made from mixtures of solid and liquid lipids were described to combine controlled release characteristics with higher drug loading capacities than solid lipid nanoparticles (SLN). It has been proposed that these nanostructured lipid carriers (NLC) are composed of oily droplets which solubilize the drug and which are embedded in a solid lipid matrix. The structures of SLN and NLC based on glyceryl behenate and medium chain triglycerides were characterized by photon correlation spectroscopy (PCS) and laser diffraction (LD), field-flow fractionation (FFF) with multi-angle light scattering detection (MALS), and cryo transmission electron microscopy (cryo TEM). PCS indicates that SLN and NLC differ from a nanoemulsion with respect to Brownian motion due to asymmetric particle shapes. Non-spherical particles, in case of SLN and NLC, lead to higher polydispersity indices compared to the nanoemulsion. In FFF, the nanodroplets elute much earlier than SLN- and NLC-platelets although their PCS and LD data show similar particle sizes. In TEM platelet (for SLN), oil loaded platelet ("nanospoons"; for NLC) and droplet (for nanoemulsion) structures were observed. In contrast to literature reports, the investigated SLN appear as thin platelets. NLC are found to be lipid platelets with oil spots sticking on the surface. Very short diffusion pathways in platelets, increased water-lipid interfaces and low drug incorporation in crystalline lipids are the drawback of SLN and NLC compared to conventional nanoemulsions.

  20. Analysis of β-glucan molar mass from barley malt and brewer's spent grain with asymmetric flow field-flow fractionation (AF4) and their association to proteins.

    PubMed

    Zielke, Claudia; Teixeira, Cristina; Ding, Huihuang; Cui, Steve; Nyman, Margareta; Nilsson, Lars

    2017-02-10

    β-Glucan benefits are related with its molar mass and it would be of interest to better understand how this parameter can be changed by processing and variety for design of food with specific health effects. For this purpose, extracts from barley malts and brewers' spent grain, processed at different conditions, were analysed regarding β-glucan content, molar mass, and protein content. Molar mass distribution was assessed using asymmetric flow field-flow fractionation (AF4) with multiangle light scattering (MALS), differential refractive index (dRI) and fluorescence (FL) detection. β-Glucan was detected in a wide molar mass range, <2000 to approximately 6.7×10(6)g/mol. Differences in molar masses were more noticeable between barley varieties and steeping malting conditions than by mashing of malt. Barley products processed to preserve β-glucan contained more β-glucan of high molar mass with potential to shift the fermentation site to the distal colon. Enzymatic degradation of proteins indicated presence of aggregates containing β-glucan and protein.

  1. Separation and size distribution of red blood cells of diverse size, shape, and origin by flow/hyperlayer field-flow fractionation.

    PubMed

    Barman, B N; Ashwood, E R; Giddings, J C

    1993-07-01

    Red blood cells (RBCs) from human, equine, canine, feline, and bovine whole blood samples have been separated and characterized by high-speed flow/hyperlayer field-flow fractionation (Fl/HyFFF). The elution-based separation of RBCs by this method is based mainly on the size and shape of the cell particles. The typical separation time for RBCs is less than 3 min. Size distributions can be derived from the fractograms of cell samples using a calibration plot based on retention data for uniform polystyrene beads. The method is shown to be effective both to separate and to characterize cell populations, including those with cells of abnormal shape and size. In order to investigate differences in cell morphology, shape and size changes induced by 500,000 Da Dextran were monitored. The changes in the Fl/HyFFF elution profiles indicate that the RBCs decrease in size but become partially aggregated in the presence of the dextran. These changes were found to depend on polymer concentration and specific blood samples. Some of the results from Fl/HyFFF were compared with those from the Coulter counter and from microscopy.

  2. Size separations of starch of different botanical origin studied by asymmetrical-flow field-flow fractionation and multiangle light scattering.

    PubMed

    Wahlund, Karl-Gustav; Leeman, Mats; Santacruz, Stalin

    2011-02-01

    Asymmetrical-flow field-flow fractionation combined with multiangle light scattering and refractive index detection has been revealed to be a powerful tool for starch characterization. It is based on size separation according to the hydrodynamic diameter of the starch components. Starch from a wide range of different botanical sources were studied, including normal starch and high-amylose and high-amylopectin starch. The starch was dissolved by heat treatment at elevated pressure in a laboratory autoclave. This gave clear solutions with no granular residues. Amylose retrogradation was prevented by using freshly dissolved samples. Programmed cross flow starting at 1.0 mL min(-1) and decreasing exponentially with a half-life of 4 min was utilised. The starches showed two size populations representing mainly amylose and mainly amylopectin with an overlapping region where amylose and amylopectin were possibly co-eluted. Most of the first population had molar masses below 10(6) g mol(-1), and most of the second size population had molar masses above 10(7) g mol(-1). Large differences were found in the relative amounts of the two populations, the molar mass, and hydrodynamic diameters, depending on the plant source and its varieties.

  3. Characterization of the molar mass distribution of macromolecules in beer for different mashing processes using asymmetric flow field-flow fractionation (AF4) coupled with multiple detectors.

    PubMed

    Choi, Jaeyeong; Zielke, Claudia; Nilsson, Lars; Lee, Seungho

    2017-07-01

    The macromolecular composition of beer is largely determined by the brewing and the mashing process. It is known that the physico-chemical properties of proteinaceous and polysaccharide molecules are closely related to the mechanism of foam stability. Three types of "American pale ale" style beer were prepared using different mashing protocols. The foam stability of the beers was assessed using the Derek Rudin standard method. Asymmetric flow field-flow fractionation (AF4) in combination with ultraviolet (UV), multiangle light scattering (MALS) and differential refractive index (dRI) detectors was used to separate the macromolecules present in the beers and the molar mass (M) and molar mass distributions (MD) were determined. Macromolecular components were identified by enzymatic treatments with β-glucanase and proteinase K. The MD of β-glucan ranged from 10(6) to 10(8) g/mol. In addition, correlation between the beer's composition and foam stability was investigated (increased concentration of protein and β-glucan was associated with increased foam stability).

  4. Different elution modes and field programming in gravitational field-flow fractionation. III. Field programming by flow-rate gradient generated by a programmable pump.

    PubMed

    Plocková, J; Chmelík, J

    2001-05-25

    Gravitational field-flow fractionation (GFFF) utilizes the Earth's gravitational field as an external force that causes the settlement of particles towards the channel accumulation wall. Hydrodynamic lift forces oppose this action by elevating particles away from the channel accumulation wall. These two counteracting forces enable modulation of the resulting force field acting on particles in GFFF. In this work, force-field programming based on modulating the magnitude of hydrodynamic lift forces was implemented via changes of flow-rate, which was accomplished by a programmable pump. Several flow-rate gradients (step gradients, linear gradients, parabolic, and combined gradients) were tested and evaluated as tools for optimization of the separation of a silica gel particle mixture. The influence of increasing amount of sample injected on the peak resolution under flow-rate gradient conditions was also investigated. This is the first time that flow-rate gradients have been implemented for programming of the resulting force field acting on particles in GFFF.

  5. Experimental design methodology applied to the study of channel dimensions on the elution of red blood cells in gravitational field flow fractionation.

    PubMed

    Rasouli, S; Assidjo, E; Chianéa, T; Cardot, P J

    2001-04-15

    Field flow fractionation (FFF) separation techniques have gained considerable success with micron-sized species. Living red blood cells (RBCs) of any origin have emerged as ideal models for cell separation development. Their elution mode is now described as "Lift-Hyperlayer". Certain separator dimension parameters are known to play a key role in the separation and band spreading process. Systematic studies of channel dimensions effects on RBC retention, band spreading, peak capacity and on a novel parameter described as "Particle Selectivity" were set up by means of a two-level factorial experimental design. From experimental results and statistical calculations it is confirmed that channel thickness plays a major role in retention ratio, peak variance, peak capacity and particle selectivity. Channel breadth strongly influences plate height, with lower impact on peak capacity and particle selectivity. Retention ratio, peak variance and peak capacity observed results are modulated by second-order interactions between channel dimensions. Preliminary rules for channel configurations are therefore set up and depend on separation goals. It is shown that a very polydisperse population is best disentangled in a thin and narrow channel whatever its length. If a mixture of many different micron-sized species is considered (each of limited polydispersities); a thick and broad channel should be preferred, with length modulating peak capacity to disentangle this polymodal mixture.

  6. Combining gas-phase electrophoretic mobility molecular analysis (GEMMA), light scattering, field flow fractionation and cryo electron microscopy in a multidimensional approach to characterize liposomal carrier vesicles

    PubMed Central

    Gondikas, Andreas; von der Kammer, Frank; Hofmann, Thilo; Marchetti-Deschmann, Martina; Allmaier, Günter; Marko-Varga, György; Andersson, Roland

    2017-01-01

    For drug delivery, characterization of liposomes regarding size, particle number concentrations, occurrence of low-sized liposome artefacts and drug encapsulation are of importance to understand their pharmacodynamic properties. In our study, we aimed to demonstrate the applicability of nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyser (nES GEMMA) as a suitable technique for analyzing these parameters. We measured number-based particle concentrations, identified differences in size between nominally identical liposomal samples, and detected the presence of low-diameter material which yielded bimodal particle size distributions. Subsequently, we compared these findings to dynamic light scattering (DLS) data and results from light scattering experiments coupled to Asymmetric Flow-Field Flow Fractionation (AF4), the latter improving the detectability of smaller particles in polydisperse samples due to a size separation step prior detection. However, the bimodal size distribution could not be detected due to method inherent limitations. In contrast, cryo transmission electron microscopy corroborated nES GEMMA results. Hence, gas-phase electrophoresis proved to be a versatile tool for liposome characterization as it could analyze both vesicle size and size distribution. Finally, a correlation of nES GEMMA results with cell viability experiments was carried out to demonstrate the importance of liposome batch-to-batch control as low-sized sample components possibly impact cell viability. PMID:27639623

  7. Asymmetric flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry for the quantification of quantum dots bioconjugation efficiency.

    PubMed

    Menéndez-Miranda, Mario; Encinar, Jorge Ruiz; Costa-Fernández, José M; Sanz-Medel, Alfredo

    2015-11-27

    Hyphenation of asymmetric flow field-flow fractionation (AF4) to an on-line elemental detection (inductively coupled plasma-mass spectrometry, ICP-MS) is proposed as a powerful diagnostic tool for quantum dots bioconjugation studies. In particular, conjugation effectiveness between a "model" monoclonal IgG antibody (Ab) and CdSe/ZnS core-shell Quantum Dots (QDs), surface-coated with an amphiphilic polymer, has been monitored here by such hybrid AF4-ICP-MS technique. Experimental conditions have been optimized searching for a proper separation between the sought bioconjugates from the eventual free reagents excesses employed during the bioconjugation (QDs and antibodies). Composition and pH of the carrier have been found to be critical parameters to ensure an efficient separation while ensuring high species recovery from the AF4 channel. An ICP-MS equipped with a triple quadropole was selected as elemental detector to enable sensitive and reliable simultaneous quantification of the elemental constituents, including sulfur, of the nanoparticulated species and the antibody. The hyphenated technique used provided nanoparticle size-based separation, elemental detection, and composition analysis capabilities that turned out to be instrumental in order to investigate in depth the Ab-QDs bioconjugation process. Moreover, the analytical strategy here proposed allowed us not only to clearly identify the bioconjugation reaction products but also to quantify nanoparticle:antibodies bioconjugation efficiency. This is a key issue in future development of analytical and bioanalytical photoluminescent QDs applications.

  8. Ultraviolet-B radiation mobilizes uranium from uranium-dissolved organic carbon complexes in aquatic systems, demonstrated by asymmetrical flow field-flow fractionation.

    PubMed

    Nehete, Sachin Vilas; Christensen, Terje; Salbu, Brit; Teien, Hans-Christian

    2017-05-05

    Humic substances have a tendency to form complexes with metal ions in aquatic medium, impacting the metal mobility, decreasing bioavailability and toxicity. Ultraviolet-B (UV-B) radiation exposure degrades the humic substance, changes their molecular weight distribution and their metal binding capacity in aquatic medium. In this study, we experimented the effect of UV-B radiation on the uranium complexed with fulvic acids and humic acids in a soft water system at different pH, uranium concentrations and radiant exposure. The concentration and distribution of uranium in a complexed form were investigated by asymmetrical flow field-flow fractionation coupled to multi detection technique (AsFlFFF-UV-ICP-MS). The major concentration of uranium present in complexes was primarily associated with average and higher molecular weight fulvic and humic acids components. The concentration of uranium in a complexed form increased with increasing fulvic and humic acid concentrations as well as pH of the solution. The higher molecular weight fraction of uranium was degraded due to the UV-B exposure, transforming about 50% of the uranium-dissolved organic carbon complexes into low molecular weight uranium species in complex form with organic ligands and/or free form. The result also suggests AsFlFFF-UV-ICP-MS to be an important separation and detection technique for understanding the interaction of radionuclides with dissolved organic matter, tracking size distribution changes during degradation of organic complexes for understanding mobility, bioavailability and ecosystem transfer of radionuclides as well as metals. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Analysis of self-assembled cationic lipid-DNA gene carrier complexes using flow field-flow fractionation and light scattering.

    PubMed

    Lee, H; Williams, S K; Allison, S D; Anchordoquy, T J

    2001-02-15

    Self-assembled cationic lipid-DNA complexes have shown an ability to facilitate the delivery of heterologous DNA across outer cell membranes and nuclear membranes (transfection) for gene therapy applications. While the size of the complex and the surface charge (which is a function of the lipid-to-DNA mass ratio) are important factors that determine transfection efficiency, lipid-DNA complex preparations are heterogeneous with respect to particle size and net charge. This heterogeneity contributes to the low transfection efficiency and instability of cationic lipid-DNA vectors. Efforts to define structure-activity relations and stable vector populations have been hampered by the lack of analytical techniques that can separate this type of particle and analyze both the physical characteristics and biological activity of the resulting fractions. In this study, we investigated the feasibility of flow field-flow fractionation (flow FFF) to separate cationic lipid-DNA complexes prepared at various lipid-DNA ratios. The compatibility of the lipid-DNA particles with several combinations of FFF carrier liquids and channel membranes was assessed. In addition, changes in elution profiles (or size distributions) were monitored as a function of time using on-line ultraviolet, multiangle light scattering, and refractive index detectors. Multiangle light scattering detected the formation of particle aggregates during storage, which were not observed with the other detectors. In comparison to population-averaged techniques, such as photon correlation spectroscopy, flow FFF allows a detailed examination of subtle changes in the physical properties of nonviral vectors and provides a basis for the definition of structure-activity relations for this novel class of pharmaceutical agents.

  10. Profiling of oxidized phospholipids in lipoproteins from patients with coronary artery disease by hollow fiber flow field-flow fractionation and nanoflow liquid chromatography-tandem mass spectrometry.

    PubMed

    Lee, Ju Yong; Byeon, Seul Kee; Moon, Myeong Hee

    2015-01-20

    Oxidized phospholipids (Ox-PLs) are oxidatively modified PLs that are produced during the oxidation of lipoproteins; oxidation of low density lipoproteins especially is known to be associated with the development of coronary artery disease (CAD). In this study, different lipoprotein classes (high density, low density, and very low density lipoproteins) from pooled plasma of CAD patients and pooled plasma from healthy controls were size-sorted on a semipreparative scale by multiplexed hollow fiber flow field-flow fractionation (MxHF5), and Ox-PLs that were extracted from each lipoprotein fraction were quantified by nanoflow liquid chromatography-tandem mass spectrometry (nLC-ESI-MS/MS). The present study showed that oxidation of lipoproteins occurred throughout all classes of lipoproteins with more Ox-PLs identified from CAD patient lipoproteins: molecular structures of 283 unique PL species (including 123 Ox-PLs) from controls and 315 (including 169 Ox-PLs) from patients were identified by data-dependent collision-induced dissociation experiments. It was shown that oxidation of PLs occurred primarily with hydroxylation of PL; in particular, a saturated acyl chain such as 16:0, 18:0, or even 18:1 at the sn-1 location of the glycerol backbone along with sn-2 acyl chains with at least two double bonds were identified. The acyl chain combinations commonly found for hydroxylated Ox-PLs in the lipoproteins of CAD patients were 16:0/18:2, 16:0/20:4, 18:0/18:2, and 18:0/20:4.

  11. Dielectrophoretically tunable optofluidic devices

    NASA Astrophysics Data System (ADS)

    Xu, Su; Ren, Hongwen; Wu, Shin-Tson

    2013-12-01

    Tunable optofluidic devices exhibit some unique characteristics that are not achievable in conventional solid-state photonic devices. They provide exciting opportunities for emerging applications in imaging, information processing, sensing, optical communication, lab-on-a-chip and biomedical engineering. A dielectrophoresis effect is an important physical mechanism to realize tunable optofluidic devices. Via balancing the voltage-induced dielectric force and interfacial tension, the liquid interface can be dynamically manipulated and the optical output reconfigured or adaptively tuned in real time. Dielectrophoretically tunable optofluidic devices offer several attractive features, such as rapid prototyping, miniaturization, easy integration and low power consumption. In this review paper, we first explain the underlying operation principles and then review some recent progress in this field, covering the topics of adaptive lens, beam steering, iris, grating, optical switch/attenuator and single pixel display. Finally, the future perspectives are discussed.

  12. Different elution modes and field programming in gravitational field-flow fractionation. 2. Experimental verification of the range of conditions for flow-rate and carrier liquid density programming.

    PubMed

    Plocková, J; Chmelík, J

    2000-02-04

    Gravitational field-flow fractionation utilises the Earth's gravitational field as an external force that causes the settlement of particles towards the channel accumulation wall. Hydrodynamic lift forces oppose this action by elevating of particles from the channel accumulation wall. Therefore there are several possibilities to modulate the resulting force field acting on particles in gravitational field-flow fractionation. Regarding the force field programming in gravitational field-flow fractionation, this work focused on two topics: changes of the difference between particle density and carrier liquid density in Brownian and focusing elution modes and influencing of lift forces achieved by changing the flow-rate in focusing elution mode. We have found and described the experimental conditions applicable to force field programming in the case of separations of silica gel particles by gravitational field-flow fractionation. It was shown that the effect of carrier liquid viscosity in the water-methanol system is implemented as an additional factor enhancing the desired effect of carrier liquid density. Some other forces influencing the retention behaviour of the model particles are discussed.

  13. Asymmetric Flow Field Flow Fractionation of Aqueous C60 Nanoparticles with Size Determination by Dynamic Light Scattering and Quantification by Liquid Chromatography Atmospheric Pressure Photo-Ionization Mass Spectrometry

    EPA Science Inventory

    A size separation method was developed for aqueous C60 fullerene aggregates (aqu/C60) using asymmetric flow field flow fractionation (AF4) coupled to a dynamic light scattering detector in flow through mode. Surfactants, which are commonly used in AF4, were avoided as they may al...

  14. Asymmetric Flow Field Flow Fractionation of Aqueous C60 Nanoparticles with Size Determination by Dynamic Light Scattering and Quantification by Liquid Chromatography Atmospheric Pressure Photo-Ionization Mass Spectrometry

    EPA Science Inventory

    A size separation method was developed for aqueous C60 fullerene aggregates (aqu/C60) using asymmetric flow field flow fractionation (AF4) coupled to a dynamic light scattering detector in flow through mode. Surfactants, which are commonly used in AF4, were avoided as they may al...

  15. Dissolution and nanoparticle generation behavior of Be-associated materials in synthetic lung fluid using inductively coupled plasma mass spectroscopy and flow field-flow fractionation.

    PubMed

    Huang, Wenjie; Fernandez, Diego; Rudd, Abigail; Johnson, William P; Deubner, David; Sabey, Philip; Storrs, Jason; Larsen, Rod

    2011-07-08

    Various Be-containing micro-particle suspensions were equilibrated with simulated lung fluid (SLF) to examine their dissolution behavior as well as the potential generation of nanoparticles. The motivation for this study was to explore the relationship between dissolution/particle generation behaviors of Be-containing materials relevant to Be-ore processing, and their epidemiologically indicated inhalation toxicities. Limited data suggest that BeO is associated with higher rates of beryllium sensitization (BS) and chronic beryllium disease (CBD) relative to the other five relevant materials studied: bertrandite-containing ore, beryl-containing ore, frit (a processing intermediate), Be(OH)₂ (a processing intermediate), and silica (control). These materials were equilibrated with SLF at two pH values (4.5 and 7.2) to reflect inter- and intra-cellular environments in lung tissue. Concentrations of Be, Al, and Si in SLF increased linearly during the first 20 days of equilibration, and then rose slowly, or in some cases reached a maximum, and subsequently decreased. Relative to the other materials, BeO produced relatively low Be concentration in solution at pH 7.2; and relatively high Be concentration in solution at pH 4.5 during the first 20 days of equilibration. For both pH values, however, the Be concentration in SLF normalized to Be content of the material was lowest for BeO, demonstrating that BeO was distinct among the four other Be-containing materials in terms of its persistence as a source of Be to the SLF solution. Following 149 days of equilibration, the SLF solutions were fractionated using flow-field flow fractionation (FlFFF) with detection via ICP-MS. For all materials, nanoparticles (which were formed during equilibration) were dominantly distributed in the 10-100 nm size range. Notably, BeO produced the least nanoparticle-associated Be mass (other than silica) at both pH values. Furthermore, BeO produced the highest Be concentrations in the size

  16. Detection and Quantification of Silver Nanoparticles at Environmentally Relevant Concentrations Using Asymmetric Flow Field??Flow Fractionation Online with Single Particle Inductively Coupled Plasma Mass Spectrometry

    EPA Pesticide Factsheets

    The presence of silver nanoparticles (AgNPs) in aquatic environments could potentially cause adverse impacts on ecosystems and human health. However, current understanding of the environmental fate and transport of AgNPs is still limited because their properties in complex environmental samples cannot be accurately determined. In this study, the feasibility of using asymmetric flow field-flow fractionation (AF4) connected online with single particle inductively coupled plasma mass spectrometry (spICPMS) to detect and quantify AgNPs at environmentally relevant concentrations was investigated. The AF4 channel had a thickness of 350 00b5m and its accumulation wall was a 10 kDa regenerated cellulose membrane. A 0.02 % FL-70 surfactant solution was used as an AF4 carrier. With 1.2 mL/min AF4 cross flow rate, 1.5 mL/min AF4 channel flow rate, and 5 ms spICPMS dwell time, the AF4??spICPMS can detect and quantify 40 ?? 80 nm AgNPs, as well as Ag-SiO2 nanoparticles (51.0 nm diameter Ag core and 21.6 nm SiO2 shell), with good recovery within 30 min. This system was not only effective in differentiating and quantifying different types of AgNPs with similar hydrodynamic diameters, such as in mixtures containing Ag-SiO2 core-shell nanoparticles and 40 ?? 80 nm AgNPs, but also suitable for differentiating between 40 nm AgNPs and elevated dissolved Ag content. The study results indicate that AF4??spICPMS is capable of detecting and quantifying AgNPs and other engineered

  17. Kinetic study of aggregation of milk protein and/or surfactant-stabilized oil-in-water emulsions by sedimentation field-flow fractionation.

    PubMed

    Kenta, Stella; Raikos, Vassilios; Vagena, Artemis; Sevastos, Dimitrios; Kapolos, John; Koliadima, Athanasia; Karaiskakis, George

    2013-08-30

    Milk proteins are able to facilitate the formation and stabilization of oil droplets in food emulsions. This study employed Sedimentation Field-Flow Fractionation (SdFFF) to monitor changes in particle size distribution of freshly prepared emulsions with varying weight contributions of sodium caseinate (SC) and whey protein concentrate (WPC). The effect of the addition of Tween 80 (T) on the initial droplet size was also investigated. The results indicated that emulsifying ability follows the order Tween 80>WPC>SC, with corresponding weight average droplet diameter of 0.319, 0.487 and 0.531μm respectively, when each of the above emulsifiers was used solely. The stability of sodium caseinate emulsions was studied at 30.5 and 80.0°C by measuring the particle size distribution for a period of 70h. Emulsions withstood the temperatures and exhibited an initial increase in particle size distribution caused by heat-induced droplet aggregation, followed by a decrease to approximately the initial droplet size. The rate of droplet aggregation depends on the severity of thermal processing, as revealed by the kinetics of particle aggregation during aging at different temperatures. Comparison of the experimental rate constants found from SdFFF, with those determined theoretically gives invaluable information about the oil droplet stability and the aggregation mechanism. Based on the proposed mechanistic scheme various physicochemical quantities, which are very important in explaining the stability of oil-in-water emulsions, were determined. Finally, the advantages of SdFFF in studying the aggregation of the oil-in-water droplets, in comparison with other methods used for the same purpose, are discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Characterization of aquatic dissolved organic matter by asymmetrical flow field-flow fractionation coupled to UV-Visible diode array and excitation emission matrix fluorescence.

    PubMed

    Guéguen, Céline; Cuss, Chad W

    2011-07-08

    Flow field-flow fractionation (FlFFF) with on-line UV/Visible diode array detector (DAD) and excitation emission matrix (EEM) fluorescence detector has been developed for the characterization of optical properties of aquatic dissolved organic matter (DOM) collected in the Otonabee River (Ontario, Canada) and Athabasca River (Alberta, Canada). The molecular weight (MW) distribution of DOM was estimated using a series of organic macromolecules ranging from 479 to 66,000 Da. Both the number-average (M(n)) and weight-average (M(w)) molecular weights of Suwannee River fulvic acid (SRFA) and Suwannee River humic acid (SRHA) determined using these macromolecular standards were comparable to those obtained using polystyrenesulfonate (PSS) standards, suggesting that organic macromolecules can be used to estimate MW of natural organic colloids. The MW of eight river DOM samples determined by this method was found to have an M(n) range of 0.8-1.1 kDa, which agrees with available literature estimates. The FlFFF-DAD-EEM system provided insight into the MW components of river DOM including the optical properties by on-line absorbance and fluorescence measurement. A red-shift in emission and excitation wavelength maxima associated with lower spectral slope ratios (S(R)=S₂₇₅₋₂₉₅:S₃₅₀₋₄₀₀) was related to higher MW DOM. However, DOM of different origins at similar MW also showed significant difference in optical properties. A difference of 47 and 40 nm in excitation and emission peak C maxima was found. This supports the hypothesis that river DOM is not uniform in size and optical composition. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Effect of cationic monomer content on polyacrylamide copolymers by frit-inlet asymmetrical flow field-flow fractionation/multi-angle light scattering.

    PubMed

    Lee, Hyejin; Kim, Jin Yong; Choi, Woonjin; Moon, Myeong Hee

    2017-06-23

    In this study, ultrahigh-molecular-weight (MW) (>10(7)Da) cationic polyacrylamides (C-PAMs), which are water-soluble polymers used in waste water treatment, were characterized using frit-inlet asymmetrical flow field-flow fractionation coupled with multi-angle light scattering and differential refractive detection. C-PAMs copolymerized with acryloxyethyltrimethyl ammonium chloride (DAC) were prepared by varying the feed amount of cationic monomer, polymerization method (solution vs. emulsion), and degree of branching. The MW of the copolymers prepared using emulsion polymerization (10(7)-10(9)Da) was generally larger than that of copolymers prepared using solution polymerization (4×10(7)-10(8)Da). When the amount of cationic monomer was increased from 10 to 55mol% in solution polymerization, hydrophobic contraction of the core induced formation of more compact C-PAMs. The copolymers prepared using emulsion polymerization formed highly aggregated or supercoil structures owing to increased intermolecular hydrophobic interaction when less cationic monomer was used. However, the MW decreased with increased cationic group content. In addition, C-PAMs larger than ∼10(8)Da prepared using the emulsion method were separated by steric/hyperlayer elution mode while those in the 10(7)-10(8)Da range were analyzed in either normal or steric/hyperlayer mode depending on the decay patterns of field programming. Moreover, branched copolymers were found to be resolved with different elution modes under the same field decay pattern depending on the degree of branching: steric/hyperlayer for low-branching and normal for high-branching C-PAMs. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Comparison of the molecular mass and optical properties of colored dissolved organic material in two rivers and coastal waters by flow field-flow fractionation.

    PubMed

    Zanardi-Lamardo, Eliete; Clark, Catherine D; Moore, Cynthia A; Zika, Rod G

    2002-07-01

    Colored dissolved organic material (CDOM) is an important sunlight absorbing substance affecting the optical properties of natural waters. However, little is known about its structural and optical properties mainly due to its complex matrix and the limitation of the techniques available. A comparison of two southwestern Florida rivers [the Caloosahatchee River (CR) and the Shark River (SR)] was done in terms of molecular mass (MM) and diffusion coefficients (D). The novel technique Frit inlet/frit outlet-flow field-flow fractionation (FIFO-FIFFF) with absorbance and fluorescence detectors was used to determine these properties. The SR receives organic material from the Everglades. By contrast, the CR arises from Lake Okeechobee in central Florida, receiving anthropogenic inputs, farming runoff, and natural organics. Both rivers discharge to the Gulf of Mexico. Fluorescence identified, for both rivers, two different MM distributions in low salinity water samples: the first was centered at approximately 1.7 kDa (CR) and approximately 2 kDa (SR); the second centered at approximately 13 kDa for both rivers, which disappeared gradually in the river plumes to below detection limit in coastal waters. Absorbance detected only one MM distribution centered at approximately 2 kDa (CR) and 2.2-2.4 kDa (SR). Fluorescence in general peaked at a lower MM than absorbance, suggesting a different size distribution for fluorophores vs chromophores. A photochemical study showed that, after sunlight, irradiated freshwater samples have similar characteristics to more marine waters, including a shift in MM distribution of chromophores. The differences observed between the rivers in the optical characteristics, MM distributions, and D values suggest that the CDOM sources, physical, and photochemical degradation processes are different for these two rivers.

  1. Extraction of hyaluronic acid (HA) from rooster comb and characterization using flow field-flow fractionation (FlFFF) coupled with multiangle light scattering (MALS).

    PubMed

    Kang, Dong Young; Kim, Won-Suk; Heo, In Sook; Park, Young Hun; Lee, Seungho

    2010-11-01

    Hyaluronic acid (HA) was extracted in a relatively large scale from rooster comb using a method similar to that reported previously. The extraction method was modified to simplify and to reduce time and cost in order to accommodate a large-scale extraction. Five hundred grams of frozen rooster combs yielded about 500 mg of dried HA. Extracted HA was characterized using asymmetrical flow field-flow fractionation (AsFlFFF) coupled online to a multiangle light scattering detector and a refractive index detector to determine the molecular size, molecular weight (MW) distribution, and molecular conformation of HA. For characterization of HA, AsFlFFF was operated by a simplified two-step procedure, instead of the conventional three-step procedure, where the first two steps (sample loading and focusing) were combined into one to avoid the adsorption of viscous HA onto the channel membrane. The simplified two-step AsFlFFF yielded reasonably good separations of HA molecules based on their MWs. The weight average MW (M(w) ) and the average root-mean-square (RMS) radius of HA extracted from rooster comb were 1.20×10(6) and 94.7 nm, respectively. When the sample solution was filtered through a 0.45 μm disposable syringe filter, they were reduced down to 3.8×10(5) and 50.1 nm, respectively. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Characterization and quantification of silver nanoparticles in nutraceuticals and beverages by asymmetric flow field flow fractionation coupled with inductively coupled plasma mass spectrometry.

    PubMed

    Ramos, K; Ramos, L; Cámara, C; Gómez-Gómez, M M

    2014-12-05

    This study evaluated the feasibility of asymmetric flow field flow fractionation coupled with inductively coupled plasma mass spectrometry (AF4-ICP-MS) for separation, characterization and quantification of silver nanoparticles (AgNPs) in complex nutraceutical and beverage samples. For improved determination, different analysis conditions were proposed depending on the NP size, i.e. below 20 nm and in the 20-60 nm range. After optimization of the different experimental parameters affecting the AF4 separation process and the analyte detection, the proposed methods showed a wide dynamic linear range (i.e., in the 10-1000 μg L(-1)) and limits of detection below 28 ng L(-1). A previous probe ultrasonication for 90 s (corresponding to 45 pulses of 2 s) of the tested samples resulted in complete AgNPs disaggregation. As a result, a fast accurate determination was achieved (complete analysis was done in ca. 37 min). The practicality of the proposed methodology for the intended determination was demonstrated by successful determination of the AgNPs present in a variety of nutraceuticals and a beverage at concentration levels in the 0.7-29.5×10(3) μg L(-1) range. A good agreement was observed among these concentration data and those determined by more conventional sample preparation techniques, such as ultracentrifugation and acid digestion. Also, the estimated NP sizes using AF4 compared satisfactorily with those determined by image techniques, i.e. transmission electron microscopy (TEM). All together demonstrated the utility of this novel analytical methodology for the analysis of AgNPs of different size in complex matrices. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Characterization of cationic polymers by asymmetric flow field-flow fractionation and multi-angle light scattering-A comparison with traditional techniques.

    PubMed

    Wagner, Michael; Pietsch, Christian; Tauhardt, Lutz; Schallon, Anja; Schubert, Ulrich S

    2014-01-17

    In the field of nanomedicine, cationic polymers are the subject of intensive research and represent promising carriers for genetic material. The detailed characterization of these carriers is essential since the efficiency of gene delivery strongly depends on the properties of the used polymer. Common characterization methods such as size exclusion chromatography (SEC) or mass spectrometry (MS) suffer from problems, e.g. missing standards, or even failed for cationic polymers. As an alternative, asymmetrical flow field-flow fractionation (AF4) was investigated. Additionally, analytical ultracentrifugation (AUC) and (1)H NMR spectroscopy, as well-established techniques, were applied to evaluate the results obtained by AF4. In this study, different polymers of molar masses between 10 and 120kgmol(-1) with varying amine functionalities in the side chain or in the polymer backbone were investigated. To this end, some of the most successful gene delivery agents, namely linear poly(ethylene imine) (LPEI) (only secondary amines in the backbone), branched poly(ethylene imine) (B-PEI) (secondary and tertiary amino groups in the backbone, primary amine end groups), and poly(l-lysine) (amide backbone and primary amine side chains), were characterized. Moreover, poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), poly(2-(amino)ethyl methacrylate) (PAEMA), and poly(2-(tert-butylamino)ethyl methacrylate) (PtBAEMA) as polymers with primary, secondary, and tertiary amines in the side chain, have been investigated. Reliable results were obtained for all investigated polymers by AF4. In addition, important factors for all methods were evaluated, e.g. the influence of different elution buffers and AF4 membranes. Besides this, the correct determination of the partial specific volume and the suppression of the polyelectrolyte effect are the most critical issues for AUC investigations.

  4. Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry.

    PubMed

    Helsper, Johannes P F G; Peters, Ruud J B; van Bemmel, Margaretha E M; Rivera, Zahira E Herrera; Wagner, Stephan; von der Kammer, Frank; Tromp, Peter C; Hofmann, Thilo; Weigel, Stefan

    2016-09-01

    Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry (ICPMS) for chemical characterization. The aF4-ICPMS conditions were optimised and validated for linearity, limit of detection, recovery, repeatability and reproducibility, all indicating good performance. Multi-element detection with aF4-ICPMS showed that some commercial pigments contained zirconium co-eluting with titanium in aF4. The other two TiMs, NM103 and NM104, contained aluminium as integral part of the titanium peak eluting in aF4. The materials were characterised using various size determination techniques: retention time in aF4, aF4 hyphenated with multi-angle laser light spectrometry (MALS), single particle ICPMS (spICPMS), scanning electron microscopy (SEM) and particle tracking analysis (PTA). PTA appeared inappropriate. For the other techniques, size distribution patterns were quite similar, i.e. high polydispersity with diameters from 20 to >700 nm, a modal peak between 200 and 500 nm and a shoulder at 600 nm. Number-based size distribution techniques as spICPMS and SEM showed smaller modal diameters than aF4-UV, from which mass-based diameters are calculated. With aF4-MALS calculated, light-scattering-based "diameters of gyration" (Øg) are similar to hydrodynamic diameters (Øh) from aF4-UV analyses and diameters observed with SEM, but much larger than with spICPMS. A Øg/Øh ratio of about 1 indicates that the TiMs are oblate spheres or fractal aggregates. SEM observations confirm the latter structure. The rationale for differences in modal peak diameter is discussed.

  5. Optimisation of asymmetric flow field-flow fractionation for the characterisation of nanoparticles in coated polydisperse TiO2 with applications in food and feed.

    PubMed

    Omar, J; Boix, A; Kerckhove, G; von Holst, C

    2016-12-01

    Titanium dioxide (TiO2) has various applications in consumer products and is also used as an additive in food and feeding stuffs. For the characterisation of this product, including the determination of nanoparticles, there is a strong need for the availability of corresponding methods of analysis. This paper presents an optimisation process for the characterisation of polydisperse-coated TiO2 nanoparticles. As a first step, probe ultrasonication was optimised using a central composite design in which the amplitude and time were the selected variables to disperse, i.e., to break up agglomerates and/or aggregates of the material. The results showed that high amplitudes (60%) favoured a better dispersion and time was fixed in mid-values (5 min). In a next step, key factors of asymmetric flow field-flow fraction (AF4), namely cross-flow (CF), detector flow (DF), exponential decay of the cross-flow (CFexp) and focus time (Ft), were studied through experimental design. Firstly, a full-factorial design was employed to establish the statistically significant factors (p < 0.05). Then, the information obtained from the full-factorial design was utilised by applying a central composite design to obtain the following optimum conditions of the system: CF, 1.6 ml min(-1); DF, 0.4 ml min(-1); Ft, 5 min; and CFexp, 0.6. Once the optimum conditions were obtained, the stability of the dispersed sample was measured for 24 h by analysing 10 replicates with AF4 in order to assess the performance of the optimised dispersion protocol. Finally, the recovery of the optimised method, particle shape and particle size distribution were estimated.

  6. Optimisation of asymmetric flow field-flow fractionation for the characterisation of nanoparticles in coated polydisperse TiO2 with applications in food and feed

    PubMed Central

    Omar, J.; Boix, A.; Kerckhove, G.; von Holst, C.

    2016-01-01

    ABSTRACT Titanium dioxide (TiO2) has various applications in consumer products and is also used as an additive in food and feeding stuffs. For the characterisation of this product, including the determination of nanoparticles, there is a strong need for the availability of corresponding methods of analysis. This paper presents an optimisation process for the characterisation of polydisperse-coated TiO2 nanoparticles. As a first step, probe ultrasonication was optimised using a central composite design in which the amplitude and time were the selected variables to disperse, i.e., to break up agglomerates and/or aggregates of the material. The results showed that high amplitudes (60%) favoured a better dispersion and time was fixed in mid-values (5 min). In a next step, key factors of asymmetric flow field-flow fraction (AF4), namely cross-flow (CF), detector flow (DF), exponential decay of the cross-flow (CFexp) and focus time (Ft), were studied through experimental design. Firstly, a full-factorial design was employed to establish the statistically significant factors (p < 0.05). Then, the information obtained from the full-factorial design was utilised by applying a central composite design to obtain the following optimum conditions of the system: CF, 1.6 ml min–1; DF, 0.4 ml min–1; Ft, 5 min; and CFexp, 0.6. Once the optimum conditions were obtained, the stability of the dispersed sample was measured for 24 h by analysing 10 replicates with AF4 in order to assess the performance of the optimised dispersion protocol. Finally, the recovery of the optimised method, particle shape and particle size distribution were estimated. PMID:27650879

  7. Effect of surfactant on retention behaviors of polystyrene latex particles in sedimentation field-flow fractionation: effective boundary slip model approach.

    PubMed

    Kim, Sun Tae; Rah, Kyunil; Lee, Seungho

    2012-07-24

    A retention theory in sedimentation field-flow fractionation (SdFFF) was developed by exploiting the effective slip boundary condition (BC) that allows a finite velocity for particles to have at the wall, thereby alleviating the limitations set by the no-slip BC constraint bound to the standard retention theory (SRT). This led to an expression for the retention ratio R as R = (R(o) + v*(b))/(R(o) + v*(b)), where R(o) is the sterically corrected SRT retention ratio and v*(b) is the reduced boundary velocity. Then, v*(b) was modeled as v*(b) = v*(b,o)/[1 + (7K*S(o))(1/2)], where S(o) is the surfactant (FL-70) concentration and K* is the distribution coefficient associated with the langmuirian isotherm of the apparent effective mass against S(o). We applied this to study the surfactant effect on the retention behaviors of polystyrene (PS) latex beads of 170-500 nm in diameter. As a result, an empirical relation was found to hold between v*(b,o) and d(o) (estimated from R(o) at S(o) = 0) as v*(b,o) - v*(o,o)[1 - (d(c)/d(o))], where v*(o,o) is the asymptotic value of v*(b,o) in the vanishing d(c)/d(o) limit and d(c) is the cutoff value at which v*(b,o) would vanish. According to the present approach, the no-slip BC (v*(b,o) = 0) was predicted to recover when d(o) ∼ d(c), and the boundary slip effect could be significant for S(o) ≤ 0.05%, particularly for large latex beads.

  8. Top-down lipidomic analysis of human lipoproteins by chip-type asymmetrical flow field-flow fractionation-electrospray ionization-tandem mass spectrometry.

    PubMed

    Kim, Ki Hun; Lee, Ju Yong; Lim, Sangsoo; Moon, Myeong Hee

    2013-03-08

    This study demonstrates the potential utility of on-line chip-type asymmetrical flow field-flow fractionation (cAF4) and electrospray ionization tandem mass spectrometry (ESI-MS-MS) for the top-down lipidomic analysis of human lipoproteins. Utilizing a cAF4, which is a miniaturized AF4 channel operated with a micro flow rate regime, enabled high density lipoprotein (HDL) and low density lipoprotein (LDL) to be separated by hydrodynamic diameter in an aqueous solution with the simultaneous desalting of lipoproteins. On-line desalting was found to enhance the ionization of lipoproteinic lipid molecules during the feeding of cAF4 effluent to ESI-MS when compared to the direct infusion of lipoproteins to MS. An evaluation of top-down lipidomic analysis was performed to test the efficiency of in-source fragmentation during cAF4-ESI-MS in the dissociation of lipoprotein particles into individual lipid molecules. This study demonstrates the structural identification of the following lipid classes: phosphatidylcholines (PCs), cholesteryl esters (CEs), and regioisomers of triacylglycerols (TAGs) having an identical mass but different acyl chains and dimeric forms of TAGs in the positive ion mode, and phosphatidylglycerols (PGs), phosphatidic acids (PAs), phosphatidyinositols (PIs), and their lyso species in the negative ion mode. The developed method was applied to plasma samples from patients with coronary artery disease (CAD) for the separation of HDL and LDL and for the simultaneous analysis of lipoproteinic lipids, resulting in the identification of 11 PCs, 9 PGs, 4 PAs, 2 PIs, 2 PEs, 18 TAGs, and 6 CEs. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Prospects and difficulties in TiO₂ nanoparticles analysis in cosmetic and food products using asymmetrical flow field-flow fractionation hyphenated to inductively coupled plasma mass spectrometry.

    PubMed

    López-Heras, Isabel; Madrid, Yolanda; Cámara, Carmen

    2014-06-01

    In this work, we proposed an analytical approach based on asymmetrical flow field-flow fractionation combined to an inductively coupled plasma mass spectrometry (AsFlFFF-ICP-MS) for rutile titanium dioxide nanoparticles (TiO2NPs) characterization and quantification in cosmetic and food products. AsFlFFF-ICP-MS separation of TiO2NPs was performed using 0.2% (w/v) SDS, 6% (v/v) methanol at pH 8.7 as the carrier solution. Two problems were addressed during TiO2NPs analysis by AsFlFFF-ICP-MS: size distribution determination and element quantification of the NPs. Two approaches were used for size determination: size calibration using polystyrene latex standards of known sizes and transmission electron microscopy (TEM). A method based on focused sonication for preparing NPs dispersions followed by an on-line external calibration strategy based on AsFlFFF-ICP-MS, using rutile TiO2NPs as standards is presented here for the first time. The developed method suppressed non-specific interactions between NPs and membrane, and overcame possible erroneous results obtained when quantification is performed by using ionic Ti solutions. The applicability of the quantification method was tested on cosmetic products (moisturizing cream). Regarding validation, at the 95% confidence level, no significant differences were detected between titanium concentrations in the moisturizing cream prior sample mineralization (3865±139 mg Ti/kg sample), by FIA-ICP-MS analysis prior NPs extraction (3770±24 mg Ti/kg sample), and after using the optimized on-line calibration approach (3699±145 mg Ti/kg sample). Besides the high Ti content found in the studied food products (sugar glass and coffee cream), TiO2NPs were not detected.

  10. Characterization of aggregates of surface modified fullerenes by asymmetrical flow field-flow fractionation with multi-angle light scattering detection.

    PubMed

    Astefanei, Alina; Kok, Wim Th; Bäuerlein, Patrick; Núñez, Oscar; Galceran, Maria Teresa; de Voogt, Pim; Schoenmakers, Peter J

    2015-08-21

    Fullerenes are carbon nanoparticles with widespread biomedical, commercial and industrial applications. Attributes such as their tendency to aggregate and aggregate size and shape impact their ability to be transported into and through the environment and living tissues. Knowledge of these properties is therefore valuable for their human and environmental risk assessment as well as to control their synthesis and manufacture. In this work, asymmetrical flow-field flow fractionation (AF4) coupled to multi-angle light scattering (MALS) was used for the first time to study the size distribution of surface modified fullerenes with both polyhydroxyl and carboxyl functional groups in aqueous solutions having different pH (6.5-11) and ionic strength values (0-200mM) of environmental relevance. Fractionation key parameters such as flow rates, flow programming, and membrane material were optimized for the selected fullerenes. The aggregation of the compounds studied appeared to be indifferent to changes in solution pH, but was affected by changes in the ionic strength. Polyhydroxy-fullerenes were found to be present mostly as 4nm aggregates in water without added salt, but showed more aggregation at high ionic strength, with an up to 10-fold increase in their mean hydrodynamic radii (200mM), due to a decrease in the electrostatic repulsion between the nanoparticles. Carboxy-fullerenes showed a much stronger aggregation degree in water (50-100nm). Their average size and recoveries decreased with the increase in the salt concentration. This behavior can be due to enhanced adsorption of the large particles to the membrane at high ionic strength, because of their higher hydrophobicity and much larger particle sizes compared to polyhydroxy-fullerenes. The method performance was evaluated by calculating the run-to-run precision of the retention time (hydrodynamic radii), and the obtained RSD values were lower than 1%. MALS measurements showed aggregate sizes that were in good

  11. Binding and transport of rare earth elements by organic and iron-rich nanocolloids in Alaskan rivers, as revealed by field-flow fractionation and ICP-MS

    NASA Astrophysics Data System (ADS)

    Stolpe, Björn; Guo, Laodong; Shiller, Alan M.

    2013-04-01

    Water samples were collected from six small rivers in the Yukon River basin in central Alaska to examine the role of nanocolloids (0.5-40 nm) in the dynamics and transport of rare earth elements (REEs) in northern high latitude watersheds influenced by permafrost. Total dissolved (<0.45 μm) concentrations and the 'nanocolloidal size distributions' (0.5-40 nm) of UV-absorbing dissolved organic matter, Fe, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu were determined by on-line coupling of flow field-flow fractionation (FFF) with a UV-absorbance detector and ICP-MS. Total dissolved and nanocolloidal concentrations of the REEs co-varied with dissolved organic carbon (DOC) in all rivers and between spring flood and late summer baseflow. The nanocolloidal size distributions indicated the presence of three major components of nanocolloids: the 0.5-3 nm 'fulvic-rich nanocolloids' occurring throughout the sampling season, the 'organic/iron-rich nanocolloids' residing in the <8 nm size range during the spring flood, and the 4-40 nm iron-rich nanocolloids occurring during summer baseflow. REEs associated with all the three components of nanocolloids, but the proportions associated with the fulvic-rich nanocolloids during summer baseflow increased with increasing REE molar mass, which is consistent with the increase in stability of organic REE-complexes with increasing REE molar mass. Normalization of the measured REE-concentrations with the average REE-concentrations of the upper continental crust revealed a dynamic change in the physicochemical fractionation of REEs. During the spring flood, REE-binding in all the rivers was dominated by the <8 nm organic/iron-rich nanocolloids, likely being eroded from the upper organic-rich soil horizon by the strong surface runoff of snowmelt water. During the summer, the REE-binding in rivers with large groundwater input was dominated by small (<0.5 nm) organic and/or inorganic complexes, while lower proportions of the REEs

  12. Dielectrophoretic systems without embedded electrodes

    DOEpatents

    Cummings, Eric B.; Singh, Anup K.

    2006-03-21

    Method and apparatus for dielectrophoretic separation of particles in a fluid based using array of insulating structures arranged in a fluid flow channel. By utilizing an array of insulating structures, a spatially inhomogeneous electric field is created without the use of the embedded electrodes conventionally employed for dielectrophoretic separations. Moreover, by using these insulating structures a steady applied electric field has been shown to provide for dielectrophoresis in contrast to the conventional use of an alternating electric field. In a uniform array of posts, dielectrophoretic effects have been produced flows having significant pressure-driven and electrokinetic transport. Above a threshold applied electric field, filaments of concentrated and rarefied particles appear in the flow as a result of dielectrophoresis. Above a higher threshold applied voltage, dielectrophoresis produces zones of highly concentrated and immobilized particles. These patterns are strongly influenced by the angle of the array of insulating structures with respect to the mean applied electric field and the shape of the insulating structures.

  13. Continuous flow dielectrophoretic particle concentrator

    SciTech Connect

    Cummings, Eric B.

    2007-04-17

    A continuous-flow filter/concentrator for separating and/or concentrating particles in a fluid is disclosed. The filter is a three-port device an inlet port, an filter port and a concentrate port. The filter separates particles into two streams by the ratio of their dielectrophoretic mobility to their electrokinetic, advective, or diffusive mobility if the dominant transport mechanism is electrokinesis, advection, or diffusion, respectively.Also disclosed is a device for separating and/or concentrating particles by dielectrophoretic trapping of the particles.

  14. Application of an asymmetric flow field flow fractionation multi-detector approach for metallic engineered nanoparticle characterization--prospects and limitations demonstrated on Au nanoparticles.

    PubMed

    Hagendorfer, Harald; Kaegi, Ralf; Traber, Jacqueline; Mertens, Stijn F L; Scherrers, Roger; Ludwig, Christian; Ulrich, Andrea

    2011-11-14

    In this work we discuss about the method development, applicability and limitations of an asymmetric flow field flow fractionation (A4F) system in combination with a multi-detector setup consisting of UV/vis, light scattering, and inductively coupled plasma mass spectrometry (ICPMS). The overall aim was to obtain a size dependent-, element specific-, and quantitative method appropriate for the characterization of metallic engineered nanoparticle (ENP) dispersions. Thus, systematic investigations of crucial method parameters were performed by employing well characterized Au nanoparticles (Au-NPs) as a defined model system. For good separation performance, the A4F flow-, membrane-, and carrier conditions were optimized. To obtain reliable size information, the use of laser light scattering based detectors was evaluated, where an online dynamic light scattering (DLS) detector showed good results for the investigated Au-NP up to a size of 80 nm in hydrodynamic diameter. To adapt large sensitivity differences of the various detectors, as well as to guarantee long term stability and minimum contamination of the mass spectrometer a split-flow concept for coupling ICPMS was evaluated. To test for reliable quantification, the ICPMS signal response of ionic Au standards was compared to that of Au-NP. Using proper stabilization with surfactants, no difference for concentrations of 1-50 μg Au L(-1) in the size range from 5 to 80 nm for citrate stabilized dispersions was observed. However, studies using different A4F channel membranes showed unspecific particle-membrane interaction resulting in retention time shifts and unspecific loss of nanoparticles, depending on the Au-NP system as well as membrane batch and type. Thus, reliable quantification and discrimination of ionic and particular species was performed using ICPMS in combination with ultracentrifugation instead of direct quantification with the A4F multi-detector setup. Figures of merit were obtained, by comparing the

  15. Asymmetrical flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry for sizing SeNPs for packaging applications

    NASA Astrophysics Data System (ADS)

    Palomo-Siguero, María; Vera, Paula; Echegoyen, Yolanda; Nerin, Cristina; Cámara, Carmen; Madrid, Yolanda

    2017-06-01

    This paper describes the application of Asymmetrical Flow Field-Flow Fractionation (AF4) coupled to diode array detector (DAD) and inductively coupled plasma mass spectrometry (AF4-UV-ICP-MS) to characterize selenium nanoparticles (SeNPs) in an aqueous acrylic adhesive to be used in a multilayer food packaging material. SeNPs were synthesized using a solution-phase approach based on the reduction of selenite with ascorbic acid in presence of different stabilizers compatible with food industry such as polysaccharides (chitosan (poly(D-glucosamine) and hydroxyethylcellulose (HEC)) and non-ionic surfactants (Triton X-100 (t-octylphenoxypolyethoxyethanol), 2,4,7,9-tetramethyl 5decyne-4,7-diol ethoxylate, and isotridecanol ethoxylate). Several parameters such as pH, ascorbic acid and stabilizers concentration, and compatibility of the stabilizer with the adhesive were evaluated. SeNPs suspensions with spherical morphology were obtained except when isotridecanol ethoxylate was employed which provides SeNPs with a nanorod morphology. AF4-DAD-ICP-MS was further applied for sizing the different SeNPs preparations. DAD was used as detector for selecting the best AF4 separation conditions before coupling to ICP-MS to ensure unequivocal identification of NPs. AF4 calibration with polystyrene latex (PSL) beads of known sizes allowed size determination of the different SeNPs. The following estimated hydrodynamic sizes (expressed as the mean ± standard deviation, n = 6 replicates) were found: chitosan-SeNPs- (26 ± 3 nm), TritonX100-SeNPs (22 ± 10 nm) HEC- SeNPs (91 ± 8 nm) and 2,4,7,9-tetramethyl 5decyne-4,7-diol ethoxylate- SeNPs (59 ± 4 nm). The proposed methodology was successfully applied to the characterization in terms of size of aqueous acrylic adhesives containing SeNPs Results from AF4-ICP-MS and TEM shown that only those SeNPs obtained with non-ionic surfactants and HEC were compatible with the adhesive. The results reported here evidence the usefulness of AF4-ICP

  16. Silver and gold nanoparticle separation using asymmetrical flow-field flow fractionation: Influence of run conditions and of particle and membrane charges.

    PubMed

    Meisterjahn, Boris; Wagner, Stephan; von der Kammer, Frank; Hennecke, Dieter; Hofmann, Thilo

    2016-04-01

    Flow-Field Flow Fractionation (Flow-FFF), coupled with online detection systems is one of the most promising tools available for the separation and quantification of engineered nanoparticles (ENPs) in complex matrices. To correctly relate the retention of nanoparticles in the Flow-FFF-channel to the particle size, ideal separation conditions must be met. This requires optimization of the parameters that influence the separation behavior. The aim of this study was therefore to systematically investigate and evaluate the influence of parameters such as the carrier liquid, the cross flow, and the membrane material, on the separation behavior of two metallic ENPs. For this purpose the retention, recovery, and separation efficiency of sterically stabilized silver nanoparticles (AgNPs) and electrostatically stabilized gold nanoparticles (AuNPs), which represent two materials widely used in investigations on environmental fate and ecotoxicology, were investigated against a parameter matrix of three different cross-flow densities, four representative carrier solutions, and two membrane materials. The use of a complex mixture of buffers, ionic and non-ionic surfactants (FL-70 solution) together with a medium cross-flow density provided an acceptable compromise in peak quality and recovery for both types of ENPs. However, these separation conditions do not represent a perfect match for both particle types at the same time (maximized recovery at maximized retention). It could be shown that the behavior of particles within Flow-FFF channels cannot be predicted or explained purely in terms of electrostatic interactions. Particles were irreversibly lost under conditions where the measured zeta potentials suggested that there should have been sufficient electrostatic repulsion to ensure stabilization of the particles in the Flow-FFF channel resulting in good recoveries. The wide variations that we observed in ENP behavior under different conditions, together with the different

  17. Interaction of bentonite colloids with Cs, Eu, Th and U in presence of humic acid: A flow field-flow fractionation study

    NASA Astrophysics Data System (ADS)

    Bouby, Muriel; Geckeis, Horst; Lützenkirchen, Johannes; Mihai, Silvia; Schäfer, Thorsten

    2011-07-01

    The interaction of Cs(I), Eu(III), Th(IV) and U(VI) with montmorillonite colloids was investigated in natural Grimsel Test Site groundwater over a 3 years period. The asymmetric flow field-flow fractionation combined with various detectors was applied to study size variations of colloids and to monitor colloid association of trace metals. The colloids suspended directly in the low ionic strength ( I), slightly alkaline granitic groundwater ( I = 10 -3 mol/L, pH 9.6) showed a gradual agglomeration with a size distribution shift from initially 10-200 nm to 50-400 nm within over 3 years. The Ca 2+ concentration of 2.1 × 10 -4 mol/L in the ground water is believed to be responsible for the slow agglomeration due to Ca 2+ ion exchange against Li + and Na + at the permanently charged basal clay planes. Furthermore, the Ca 2+ concentration lies close to the critical coagulation concentration (CCC) of 10 -3 mol L -1 for clay colloids. Slow destabilization may delimit clay colloid migration in this specific groundwater over long time scales. Eu(III) and Th(IV) are found predominantly bound to clay colloids, while U(VI) prevails as the UO 2(OH) 3- complex and Cs(I) remains mainly as aquo ion under our experimental conditions. Speciation calculations qualitatively represent the experimental data. A focus was set on the reversibility of metal ion-colloid binding. Addition of humic acid as a competing ligand induces rapid metal ion dissociation from clay colloids in the case of Eu(III) even after previous aging for about 3 years. Interestingly only partial dissociation occurs in the case of Th(IV). Experiments and calculations prove that the humate complexes dominate the speciation of all metal ions under given conditions. The partial irreversibility of clay bound Th(IV) is presently not understood but might play an important role for the colloid-mediated transport of polyvalent actinides over wide distances in natural groundwater.

  18. Feasibility of asymmetric flow field-flow fractionation coupled to ICP-MS for the characterization of wear metal particles and metalloproteins in biofluids from hip replacement patients.

    PubMed

    Loeschner, Katrin; Harrington, Chris F; Kearney, Jacque-Lucca; Langton, David J; Larsen, Erik H

    2015-06-01

    Hip replacements are used to improve the quality of life of people with orthopaedic conditions, but the use of metal-on-metal (MoM) arthroplasty has led to poor outcomes for some patients. These problems are related to the generation of micro- to nanosized metal wear particles containing Cr, Co or other elements, but the current analytical methods used to investigate the processes involved do not provide sufficient information to understand the size or composition of the wear particles generated in vivo. In this qualitative feasibility study, asymmetric flow field-flow fractionation (AF(4)) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was used to investigate metal protein binding and the size and composition of wear metal particles present in serum and hip aspirates from MoM hip replacement patients. A well-established HPLC anion exchange chromatography (AEC) separation system coupled to ICP-MS was used to confirm the metal-protein associations in the serum samples. Off-line single particle ICP-MS (spICP-MS) analysis was used to confirm the approximate size distribution indicated by AF(4) of the wear particles in hip aspirates. In the serum samples, AF(4) -ICP-MS suggested that Cr was associated with transferrin (Tf) and Co with albumin (Alb) and an unidentified species; AEC-ICP-MS confirmed these associations and also indicated an association of Cr with Alb. In the hip aspirate sample, AF(4)-ICP-MS suggested that Cr was associated with Alb and Tf and that Co was associated with Alb and two unidentified compounds; AEC analysis confirmed the Cr results and the association of Co with Alb and a second compound. Enzymatic digestion of the hip aspirate sample, followed by separation using AF(4) with detection by UV absorption (280 nm), multi-angle light scattering and ICP-MS, suggested that the sizes of the Cr-, Co- and Mo-containing wear particles in a hip aspirate sample were in the range 40-150 nm. Off-line spICP-MS was used to confirm these

  19. Effect of size of Fe3O4 magnetic nanoparticles on electrochemical performance of screen printed electrode using sedimentation field-flow fractionation

    NASA Astrophysics Data System (ADS)

    Dou, Haiyang; Kim, Beom-Ju; Choi, Seong-Ho; Jung, Euo Chang; Lee, Seungho

    2014-10-01

    Fe3O4 magnetic nanoparticles (MNPs) and Fe3O4-deposited multi-walled carbon nanotubes (Fe3O4@MWCNTs) were synthesized by ultrasonic co-precipitation method. The surface and structural properties of Fe3O4 MNPs and Fe3O4@MWCNTs were characterized by X-ray diffraction, field emission transmission electron microscopy (FE-TEM), X-ray photoelectron spectroscopy, and dynamic light scattering (DLS). Sedimentation field-flow fractionation (SdFFF) was, for the first time, employed to study the influence of synthesis parameters on size distribution of Fe3O4 MNPs. A reasonable resolution for SdFFF analysis of Fe3O4 MNPs was obtained by a combination of 1,600 RPM, flow rate of 0.3 mL min-1, and Triton X-100. The results suggest that lower pH and higher reaction temperature tend to yield smaller Fe3O4 MNPs size. The size distribution of Fe3O4 MNPs obtained from SdFFF was compared with those obtained from TEM and DLS. Also the effect of the particle size of Fe3O4 MNPs on electrochemical property of Fe3O4@MWCNTs-treated screen printed electrode (SPE) was studied. Cyclic voltammetry revealed that SPE treated with MWCNTs yields a significantly enhanced signal than that with no treatment. The SPE signal was even further enhanced with addition of Fe3O4 MNPs. For SPE analysis of dopamine, a liner range of 0.005-0.1 mM with a correlation coefficient of 0.986 was observed. Results revealed that (1) SdFFF is a useful tool for size-based separation and characterization of MNPs; (2) Proposed methods for synthesis of Fe3O4 nanoparticles and Fe3O4@MWCNTs are mild and fast (about 30 min); (3) SPE treated with Fe3O4@MWCNTs shows potential applicability for biosensing.

  20. Size fractionation and size characterization of nanoemulsions of lipid droplets and large unilamellar lipid vesicles by asymmetric-flow field-flow fractionation/multi-angle light scattering and dynamic light scattering.

    PubMed

    Vezočnik, Valerija; Rebolj, Katja; Sitar, Simona; Ota, Katja; Tušek-Žnidarič, Magda; Štrus, Jasna; Sepčić, Kristina; Pahovnik, David; Maček, Peter; Žagar, Ema

    2015-10-30

    Asymmetric-flow field-flow fractionation technique coupled to a multi-angle light-scattering detector (AF4-MALS) was used together with dynamic light-scattering (DLS) in batch mode and transmission electron microscopy (TEM) to study the size characteristics of the trioleoylglycerol lipid droplets covered by a monolayer of sphingomyelin and cholesterol, in water phase. These lipid droplet nanoemulsions (LD) were formed by ultrasonication. In parallel, the size characteristics of large unilamellar lipid vesicles (LUV) prepared by extrusion and composed of sphingomyelin and cholesterol were determined. LD and LUV were prepared at two different molar ratios (1/1, 4/1) of sphingomyelin and cholesterol. In AF4-MALS, various cross-flow conditions and mobile phase compositions were tested to optimize the separation of LD or LUV particles. The particle radii, R, as well as the root-mean-square radii, Rrms, of LD and LUV were determined by AF4-MALS, whereas the hydrodynamic radii, Rh, were obtained by DLS. TEM visualization revealed round shape particles of LD and LUV.

  1. Hydrodynamic enhanced dielectrophoretic particle trapping

    DOEpatents

    Miles, Robin R.

    2003-12-09

    Hydrodynamic enhanced dielectrophoretic particle trapping carried out by introducing a side stream into the main stream to squeeze the fluid containing particles close to the electrodes producing the dielelectrophoretic forces. The region of most effective or the strongest forces in the manipulating fields of the electrodes producing the dielectrophoretic forces is close to the electrodes, within 100 .mu.m from the electrodes. The particle trapping arrangement uses a series of electrodes with an AC field placed between pairs of electrodes, which causes trapping of particles along the edges of the electrodes. By forcing an incoming flow stream containing cells and DNA, for example, close to the electrodes using another flow stream improves the efficiency of the DNA trapping.

  2. Accurate Size and Size-Distribution Determination of Polystyrene Latex Nanoparticles in Aqueous Medium Using Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation with Multi-Angle Light Scattering

    PubMed Central

    Kato, Haruhisa; Nakamura, Ayako; Takahashi, Kayori; Kinugasa, Shinichi

    2012-01-01

    Accurate determination of the intensity-average diameter of polystyrene latex (PS-latex) by dynamic light scattering (DLS) was carried out through extrapolation of both the concentration of PS-latex and the observed scattering angle. Intensity-average diameter and size distribution were reliably determined by asymmetric flow field flow fractionation (AFFFF) using multi-angle light scattering (MALS) with consideration of band broadening in AFFFF separation. The intensity-average diameter determined by DLS and AFFFF-MALS agreed well within the estimated uncertainties, although the size distribution of PS-latex determined by DLS was less reliable in comparison with that determined by AFFFF-MALS. PMID:28348293

  3. Particle size analyses of porous silica and hybrid silica chromatographic support particles. Comparison of flow/hyperlayer field-flow fractionation with scanning electron microscopy, electrical sensing zone, and static light scattering.

    PubMed

    Xu, Yuehong

    2008-05-16

    Porous silica and hybrid silica chromatographic support particles having particle diameters ranging approximately from 1 microm to 15 microm have been characterized by flow/hyperlayer field-flow fractionation (FFF). The particle size accuracy has been improved significantly in this work by a second-order polynomial calibration. Very good agreement between the FFF data and scanning electron microscopic (SEM) results has been achieved. The effects of particle porosity, pore sizes, and particle sizes on the particle size accuracy in electrical sensing zone (ESZ) analyses have been discussed. It has been demonstrated by computer simulation and experimental measurements that false peaks can be generated in certain particle size regions when the static light scattering (SLS) technique is applied to tightly distributed spherical chromatographic support particles.

  4. Influence of protein formulation and carrier solution on asymmetrical flow field-flow fractionation: a case study of the plant-produced recombinant anthrax protective antigen pp-PA83.

    PubMed

    Palais, Caroline; Chichester, Jessica A; Manceva, Slobodanka; Yusibov, Vidadi; Arvinte, Tudor

    2015-02-01

    Asymmetrical flow field-flow fractionation (afFFF) was used to investigate the properties of a plant-produced anthrax toxin protective antigen, pp-PA83. The afFFF fractogram consisted of two main peaks with molar masses similar to the molecular mass of pp-PA83 monomer. afFFF carrier solutions strongly influenced the ratio and the intensity of the two main peaks. These differences indicate that conformation changes in the pp-PA83 molecule occurred during the afFFF analysis. Similar fractograms were obtained for different pp-PA83 formulations when the afFFF carrier solution and the protein formulation were the same (or very similar). The data show that in specific cases, afFFF could be used to study protein conformation and document the importance of studying the influence of the carrier solution on afFFF.

  5. Separation of silver nanoparticles by hollow fiber flow field-flow fractionation: Addition of tannic acid into carrier liquid as a modifier.

    PubMed

    Saenmuangchin, Rattaporn; Mettakoonpitak, Jaruwan; Shiowatana, Juwadee; Siripinyanond, Atitaya

    2015-10-09

    A homemade hollow fiber flow-field fractionation (Hf-FlFFF) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was set-up for silver nanoparticles (AgNPs) separation by using polysulfone hollow fiber membrane (30,000 MW cutoff) as a separation channel. Tannic acid and citrate stabilized AgNPs were synthesized and introduced into Hf-FlFFF. The effects of carrier liquid and stabilizing agent on retention behavior of AgNPs were investigated. Different elution behaviors were observed as follows: with 0.02% (w/v) FL-70, all of AgNPs were eluted from Hf-FlFFF but differences in retention behaviors were observed for AgNPs with tannic acid and citrate stabilizing agents; and with 30mM TRIS buffer, only tannic acid stabilized AgNPs were eluted from Hf-FlFFF, whereas citrate stabilized AgNPs were not eluted. In this work, tannic acid addition into carrier liquid was proposed to modify the surface of AgNPs and the surface of the membrane, and thereby adjusting the retention behaviors of AgNPs. Various concentrations of tannic acid were added into FL-70 and TRIS buffer. With the use of 0.1mM tannic acid in 30mM TRIS buffer as the carrier liquid, retention behaviors of both tannic acid stabilized- and citrate stabilized-AgNPs were similar and with similar fractionation recovery.

  6. Colloidal transport and agglomeration in column studies for advanced run-off filtration facilities--particle size and time resolved monitoring of effluents with flow-field-flow-fractionation.

    PubMed

    Siepmann, R; von der Kammer, F; Förstner, U

    2004-01-01

    The efficiency of road run-off filtration facilities based on ion-exchange materials is reduced by pollutants which are transported bound to particles. To quantify the factors governing particle transport phenomena, a simplified model consisting of quartz sand-filled columns representing the filter/soil was set up. Suspensions of artificial clays, cold water-extracted natural clays, and real run-off were used as model effluents. Five experiments were performed: breakthrough of a natural soil suspension, remobilization of a natural soil suspension after ionic strength-drop, the same two experiments with a suspension of the artificial clay mineral Laponite, and the remobilization of run-off accumulated on a column at high ionic strength with an ionic strength down-gradient. Short-interval effluent fractions were analysed by flow-field-flow-fractionation (F4) to obtain the size distributions of the colloids present. The size distributions of subsequent fractions were then plotted in a staggered arrangement to give three-dimensional graphs that are time- and particle size-resolved. With this method the subsequent release of different agglomerate sizes formed on the column could be shown for the artificial clay mineral, questioning its use as a model colloid. The combined particle size- and time-resolved plots proved to be a powerful tool for monitoring colloidal solids in column effluents.

  7. Hollow-fiber flow field-flow fractionation and multi-angle light scattering investigation of the size, shape and metal-release of silver nanoparticles in aqueous medium for nano-risk assessment.

    PubMed

    Marassi, Valentina; Casolari, Sonia; Roda, Barbara; Zattoni, Andrea; Reschiglian, Pierluigi; Panzavolta, Silvia; Tofail, Syed A M; Ortelli, Simona; Delpivo, Camilla; Blosi, Magda; Costa, Anna Luisa

    2015-03-15

    Due to the increased use of silver nanoparticles in industrial scale manufacturing, consumer products and nanomedicine reliable measurements of properties such as the size, shape and distribution of these nano particles in aqueous medium is critical. These properties indeed affect both functional properties and biological impacts especially in quantifying associated risks and identifying suitable risk-mediation strategies. The feasibility of on-line coupling of a fractionation technique such as hollow-fiber flow field flow fractionation (HF5) with a light scattering technique such as MALS (multi-angle light scattering) is investigated here for this purpose. Data obtained from such a fractionation technique and its combination thereof with MALS have been compared with those from more conventional but often complementary techniques e.g. transmission electron microscopy, dynamic light scattering, atomic absorption spectroscopy, and X-ray fluorescence. The combination of fractionation and multi angle light scattering techniques have been found to offer an ideal, hyphenated methodology for a simultaneous size-separation and characterization of silver nanoparticles. The hydrodynamic radii determined by fractionation techniques can be conveniently correlated to the mean average diameters determined by multi angle light scattering and reliable information on particle morphology in aqueous dispersion has been obtained. The ability to separate silver (Ag(+)) ions from silver nanoparticles (AgNPs) via membrane filtration during size analysis is an added advantage in obtaining quantitative insights to its risk potential. Most importantly, the methodology developed in this article can potentially be extended to similar characterization of metal-based nanoparticles when studying their functional effectiveness and hazard potential.

  8. MicroPrep: chip-based dielectrophoretic purification of mitochondria.

    PubMed

    Moschallski, Meike; Hausmann, Monika; Posch, Anton; Paulus, Aran; Kunz, Nancy; Duong, Thanh Tu; Angres, Brigitte; Fuchsberger, Kai; Steuer, Heiko; Stoll, Dieter; Werner, Simon; Hagmeyer, Britta; Stelzle, Martin

    2010-08-01

    We have developed a microfluidic system--microPrep--for subcellular fractionation of cell homogenates based on dielectrophoretic sorting. Separation of mitochondria isolated from a human lymphoblastoid cell line was monitored by fluorescence microscopy and further characterized by western blot analysis. Robust high throughput and continuous long-term operation for up to 60 h of the microPrep chip system with complex biological samples became feasible as a result of a comprehensive set of technical measures: (i) coating of the inner surfaces of the chip with BSA, (ii) application of mechanical actuators to induce periodic flow patterns, (iii) efficient cooling of the device to ensure integrity of organelle, (iv) a wide channel to provide for high fluidic throughput, and (v) integration of a serial arrangement of 10 dielectrophoretic deflector units to enable separation of samples with a high particle load without clogging. Hence, microPrep yields tens of micrograms of enriched and purified mitochondria within hours. Western blots of mitochondria fractions showed that contaminating endoplasmatic reticulum was reduced by a factor 6 when compared with samples prepared by state of the art centrifugation.

  9. Examining concentrations and molecular weights of thiols in microorganism cultures and in Churchill River (Manitoba) using a fluorescent-labeling method coupled to asymmetrical flow field-flow fractionation.

    PubMed

    Mangal, Vaughn; Guéguen, Celine

    2015-06-01

    In this study, molecular weights of thiols from four laboratory cultures (Scenedesmus obliquus, Chlorella vulgaris, Euglena gracilis, and Attheya septentrionalis) and the Churchill River (Manitoba) were assessed using a fluorescent-labeling method such as monobromotrimethylammoniobimane (qBBr) and asymmetrical flow field-flow fractionation (AF4) coupled to a fluorescence detector. Concentrations of thiols in extracellular fractions ranged from 6.39 ± 3.39 to 39.2 ± 7.43 μmol g(-1), and intracellular concentrations ranged from 11.5 ± 4.52 to 41.0 ± 4.1 μmol g(-1). In addition, molecular weights (MW) of intracellular thiol ranged from 493 ± 24 to 946 ± 12 Da whereas extracellular thiol MWs varied from 443 ± 36 to 810 ± 174 Da. The novel method of combining AF4 to an on-line fluorometer and the incorporation of the thiol tag provided information regarding thiol concentration and composition of controlled and natural systems. Furthermore, the proposed methods allow for the simultaneous measurement of thiol and DOM MWs produced by microorganisms. By assessing characteristics of naturally produced thiols and lab-grown thiols, information regarding heavy metal complexation can be determined.

  10. Light-Induced Dielectrophoretic Manipulation of DNA

    PubMed Central

    Hoeb, Marco; Rädler, Joachim O.; Klein, Stefan; Stutzmann, Martin; Brandt, Martin S.

    2007-01-01

    Light-induced dielectrophoretic movement of polystyrene beads and λ-DNA is studied using thin films of amorphous hydrogenated silicon as local photoaddressable electrodes with a diameter of 4 μm. Positive (high-field seeking) dielectrophoretic movement is observed for both types of objects. The absence of strong negative (low-field seeking) dielectrophoresis of DNA at high frequencies is in agreement with the similarity of the dielectric constants of DNA and water, the real part of the dielectric function. The corresponding imaginary part of the dielectric function governed by the conductivity of DNA can be determined from a comparison of the frequency dependence of the dielectrophoretic drift velocity with the Clausius-Mossotti relation. PMID:17483160

  11. Asymmetric Flow-Field Flow Fractionation Hyphenated ICP-MS as an Alternative to Cloud Point Extraction for Quantification of Silver Nanoparticles and Silver Speciation: Application for Nanoparticles with a Protein Corona.

    PubMed

    Mudalige, Thilak K; Qu, Haiou; Linder, Sean W

    2015-07-21

    Production and application of nanoparticles in consumer products is at an all-time high due to the emerging field of nanotechnology. Direct detection and quantification of trace levels of nanoparticles within consumer products is very challenging and problematic. Although multiple methodologies are available for this purpose, each method has its own set of limitations. Herein, we developed an analytical platform consisting of asymmetric flow-field flow fractionation (AF4) coupled with inductively coupled plasma mass spectroscopy (ICP-MS) for the speciation and quantification of silver ions and silver nanoparticles at the ng/kg level (ppt). AF4 is utilized to concentrate the nanoparticles, and ICP-MS acts as the detector. The protein corona that forms upon exposure of nanoparticles to bovine serum albumin was utilized as a nanoparticle stabilization and AF4 recovery enhancement mechanism. Speciation of silver ions and nanoparticles was achieved with the assistance of penicillamine as a complexation ligand. The effect of nanoparticle size, surface coating, and ionization state toward the detection and quantification of the developed methodology was evaluated. The detection limit was found to be 4 ng/kg with the application of a 5 mL sample loop. Further application of this developed methodology on environmentally relevant samples was demonstrated by the analysis of Arkansas River water spiked with silver nanoparticles and nanoparticle spiked into humic acid solution (50 mg/L) at an environmentally relevant level.

  12. Elemental ratios for characterization of quantum-dots populations in complex mixtures by asymmetrical flow field-flow fractionation on-line coupled to fluorescence and inductively coupled plasma mass spectrometry.

    PubMed

    Menendez-Miranda, Mario; Fernandez-Arguelles, Maria T; Costa-Fernandez, Jose M; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo

    2014-08-11

    Separation and identification of nanoparticles of different composition, with similar particle diameter, coexisting in heterogeneous suspensions of polymer-coated CdSe/ZnS quantum dots (QDs) have been thoroughly assessed by asymmetric flow field-flow fractionation (AF4) coupled on-line to fluorescence and inductively coupled plasma mass spectrometry (ICPMS) detectors. Chemical characterization of any previously on-line separated nanosized species was achieved by the measurement of the elemental molar ratios of every element involved in the synthesis of the QDs, using inorganic standards and external calibration by flow injection analysis (FIA). Such elemental molar ratios, strongly limited so far to pure single nanoparticles suspensions, have been achieved with adequate accuracy by coupling for the first time an ICP-QQQ instrument to an AF4 system. This hyphenation turned out to be instrumental to assess the chemical composition of the different populations of nanoparticles coexisting in the relatively complex mixtures, due to its capabilities to detect the hardly detectable elements involved in the synthesis. Interestingly such information, complementary to that obtained by fluorescence, was very valuable to detect and identify unexpected nanosized species, present at significant level, produced during QDs synthesis and hardly detectable by standard approaches.

  13. Multielement characterization of metal-humic substances complexation by size exclusion chromatography, asymmetrical flow field-flow fractionation, ultrafiltration and inductively coupled plasma-mass spectrometry detection: a comparative approach.

    PubMed

    Bolea, E; Gorriz, M P; Bouby, M; Laborda, F; Castillo, J R; Geckeis, H

    2006-10-06

    The use of three different separation techniques, ultrafiltration (UF), high performance size exclusion chromatography (HPSEC) and asymmetrical flow field-flow fractionation (AsFlFFF), for the characterization of a compost leachate is described. The possible interaction of about 30 elements with different size fractions of humic substances (HS) has been investigated coupling these separation techniques with UV-vis absorption spectrophotometry and inductively coupled plasma-mass spectrometry (ICP-MS) as detection techniques. The organic matter is constituted by a polydisperse mixture of humic substances ranging from low molecular weights (around 1kDa) to significantly larger entities. Elements can be classified into three main groups with regard to their interaction with HS. The first group is constituted by primarily the monovalent alkaline metal ions and anionic species like B, W, Mo, As existing as oxyanions all being not significantly associated to HS. The second group consists of elements that are at least partly associated to a smaller HS size fraction (such as Ni, Cu, Cr and Co). A third group of mainly tri- and tetravalent metal ions like Al, Fe, the lanthanides, Sn and Th are rather associated to larger-sized HS fractions. The three separation techniques provide a fairly consistent size classification for most of the metal ions, even though slight disagreements were observed. The number-average molecular weight (Mn), the weight-average molecular weight (Mw) and the polydispersity (rho) parameters have been calculated both from AsFlFFF and HPSEC experiments and compared for HS and some metal-HS species. Differences in values can be partly explained by an overloading effect observed in the AsFlFFF experiments induced by electrostatic repulsion effects in the low ionic strength, high pH carrier solution. Size information obtained from ultrafiltration is not as resolved as for the other methods. Molecular weight cut-offs (MWCO) of the individual filter

  14. Flow field-flow fractionation-inductively coupled optical emission spectrometric investigation of the size-based distribution of iron complexed to phytic and tannic acids in a food suspension: implications for iron availability.

    PubMed

    Purawatt, Sopon; Siripinyanond, Atitaya; Shiowatana, Juwadee

    2007-10-01

    Flow field-flow fractionation-inductively coupled plasma optical emission spectrometry (FlFFF-ICP-OES) was applied to achieve the size-based fractionation of iron in a food suspension in order to gain insights into iron availability. The binding of iron with phytic and tannic acids, employed as model inhibitors of iron availability in foods, was investigated at pH 2.0 (representing stomach fluid), pH 5.0 (the transition stage in the upper part of the duodenum), and pH 7.0 (the small intestine). In the presence of phytic acid, iron was found as a free ion or it was associated with molecules smaller than 1 kDa at pH 2.0. Iron associated with molecules larger than 1 kDa when the pH of the mixture was raised to 5.0 and 7.0. In the presence of tannic acid, iron was again mostly associated with molecules smaller than 1 kDa at pH 2.0. However, at pH 5.0, iron and tannic acid associated in large molecules (approximately 25 kDa), while at pH 7.0, most of the iron was associated with macromolecules larger than 500 kDa. Iron size-based distributions of kale extract and tea infusion containing phytic and tannic acids, respectively, were also examined at the three pH values, with and without enzymatic digestion. Without enzymatic digestion of the kale extract and the tea infusion at pH 2.0, most of the iron was released as free ions or associated with molecules smaller than 1 kDa. At other pH values, most of the iron in the kale extract and the tea infusion was found to bind with ~2 kDa and >500 kDa macromolecules, respectively. Upon enzymatic gastrointestinal digestion, the iron was not observed to bind to macromolecules >1 kDa but <500 kDa, due to the enzymatic breakdown of large molecules to smaller ones (<1 kDa).

  15. Particle motions and segregation in dielectrophoretic microfluidics

    NASA Astrophysics Data System (ADS)

    Markarian, Nikolai; Yeksel, Mike; Khusid, Boris; Farmer, Kenneth R.; Acrivos, Andreas

    2003-09-01

    We studied, experimentally and theoretically the motion and segregation of positively polarized particles flowing through dielectrophoretic microfluidics. The batch fabrication technique which we present enables one to construct an apparatus featuring a large number of mechanically robust and chemically inert microdevices having a very low ratio of dielectrophoretic-to-fluid residence time. Several apparatuses of this type can easily be integrated into a higher-level system able to handle flow rates several orders of magnitude larger than those in a single microdevice. Experiments were conducted on microfluidics with electrodes of different sizes arranged parallel and perpendicular to the flow. The simulations of the particle motions and their segregation required no fitting parameters because the suspension properties were measured independently. We demonstrate that the presence of the interparticle dipolar interactions imposes a lower bound on the size of the electrodes below which the miniaturization of microelectrodes adversely affects the ability to position the particles with precision in preselected locations [briefly reported by Markarian et al., Appl. Phys. Lett. 82, 4839 (2003)]. When the device characteristics meet certain requirements, the theoretical predictions for the variation of the amount of the segregated particles along the channel were found to be quantitatively consistent with experimental data. Combined with the earlier test of the predictions for the particle accumulation with time in millimeter-scale channels [J. Appl. Phys. 88, 5463 (2000); 92, 2829 (2002)], this completes the experimental validation of a theory for the kinetics of dielectrophoretic phenomena in a flowing dilute suspension. The results of our studies provide the basic characteristics of the ac-field-driven particle motions and segregation in a microchannel and validate a simulation procedure needed for the design and operation of dielectrophoretic microfluidics.

  16. Dielectrophoretic Traps for Single-Particle Patterning

    PubMed Central

    Rosenthal, Adam; Voldman, Joel

    2005-01-01

    We present a novel microfabricated dielectrophoretic trap designed to pattern large arrays of single cells. Because flowing away untrapped cells is often the rate-limiting step during cell patterning, we designed the trap to be strong enough to hold particles against practical flow rates. We experimentally validated the trap strength by measuring the maximum flow rate that polystyrene beads could withstand while remaining trapped. These bead experiments have shown excellent agreement with our model predictions, without the use of fitting parameters. The model was able to provide us with a fundamental understanding of how the traps work, and additionally allowed us to establish a set of design rules for optimizing the traps for a wide range of cell sizes. We provide the foundations for an enabling technology that can be used to pattern cells in unique ways, allowing us to do novel cell biology experiments at the microscale. PMID:15613624

  17. Dielectrophoretic analysis of microbes in water.

    PubMed

    Betts, W B; Brown, A P

    1998-12-01

    Traditional microbiological methods are still used extensively for analysis of micro-organisms in water. However, they are inefficient due to a high labour input requirement, a low sample capacity, and often a long time lag before results are available. Analytical stages involving incubation and growth (enrichments and colony isolation) contribute the greatest delay in reporting, although subsequent identification can also be protracted. The use of electrometric growth analysers (measuring impedance, conductance or capacitance changes) is now more common in water microbiology. Although these instruments can provide more rapid results and provide increased handling capacity, the bacterial generation times required to provide detectable changes cause delays and suitable selective media are not fully developed for all microbes of interest. Most other recent methods have equally disappointing drawbacks and thus extensive research continues in order to realise the ambition of 'real-time' analytical microbiology. Several research groups have demonstrated the potential of dielectrophoresis in providing microbial concentration, separation and identification systems which are not limited by bacterial growth and are therefore extremely rapid. Dielectrophoresis occurs when cells are placed in non-uniform electric fields. The cells move towards the electrodes (regardless of the direction of the applied field) as determined by their dielectric properties (conductivity and permittivity) rather than by their charge as occurs in electrophoresis. Also, the polarisability of the cells, and therefore the polarity and magnitude of the dielectrophoretic force, varies as a function of the electric field frequency. Because the dielectric properties of a particular cell type have characteristic frequency-dependent components, if cell collection at electrodes is observed across a frequency range, the collection spectrum produced is distinctive for the cell type under investigation. This

  18. Dielectrophoresis and dielectrophoretic impedance detection of adenovirus and rotavirus

    NASA Astrophysics Data System (ADS)

    Nakano, Michihiko; Ding, Zhenhao; Suehiro, Junya

    2016-01-01

    The aim of this study is the electrical detection of pathogenic viruses, namely, adenovirus and rotavirus, using dielectrophoretic impedance measurement (DEPIM). DEPIM consists of two simultaneous processes: dielectrophoretic trapping of the target and measurement of the impedance change and increase in conductance with the number of trapped targets. This is the first study of applying DEPIM, which was originally developed to detect bacteria suspended in aqueous solutions, to virus detection. The dielectric properties of the viruses were also investigated in terms of their dielectrophoretic behavior. Although their estimated dielectric properties were different from those of bacteria, the trapped viruses increased the conductance of the microelectrode in a manner similar to that in bacteria detection. We demonstrated the electrical detection of viruses within 60 s at concentrations as low as 70 ng/ml for adenovirus and 50 ng/ml for rotavirus.

  19. Holding forces of single-particle dielectrophoretic traps.

    PubMed Central

    Voldman, J; Braff, R A; Toner, M; Gray, M L; Schmidt, M A

    2001-01-01

    We present experimental results and modeling on the efficacy of dielectrophoresis-based single-particle traps. Dielectrophoretic forces, caused by the interaction of nonuniform electric fields with objects, have been used to make planar quadrupole traps that can trap single beads. A simple experimental protocol was then used to measure how well the traps could hold beads against destabilizing fluid flows. These were compared with predictions from modeling and found to be in close agreement, allowing the determination of sub-piconewton forces. This not only validates our ability to model dielectrophoretic forces in these traps but also gives insight into the physical behavior of particles in dielectrophoresis-based traps. Anomalous frequency effects, not explainable by dielectrophoretic forces alone, were also encountered and attributed to electrohydrodynamic flows. Such knowledge can now be used to design traps for cell-based applications. PMID:11159423

  20. Nanoscale dielectrophoretic spectroscopy of individual immobilized mammalian blood cells.

    PubMed

    Lynch, Brian P; Hilton, Al M; Simpson, Garth J

    2006-10-01

    Dielectrophoretic force microscopy (DEPFM) and spectroscopy have been performed on individual intact surface-immobilized mammalian red blood cells. Dielectrophoretic force spectra were obtained in situ in approximately 125 ms and could be acquired over a region comparable in dimension to the effective diameter of a scanning probe microscopy tip. Good agreement was observed between the measured dielectrophoretic spectra and predictions using a single-shell cell model. In addition to allowing for highly localized dielectric characterization, DEPFM provided a simple means for noncontact imaging of mammalian blood cells under aqueous conditions. These studies demonstrate the feasibility of using DEPFM to monitor localized changes in membrane capacitance in real time with high spatial resolution on immobilized cells, complementing previous studies of mobile whole cells and cell suspensions.

  1. Dielectrophoretic manipulation of cells with spiral electrodes.

    PubMed Central

    Wang, X B; Huang, Y; Wang, X; Becker, F F; Gascoyne, P R

    1997-01-01

    Electrokinetic responses of human breast cancer MDA-MB-231 cells were studied in suspensions of conductivities 18, 56, and 160 mS/m on a microelectrode array consisting of four parallel spiral electrode elements energized with phase-quadrature signals of frequencies between 100 Hz and 100 MHz. At low frequencies cells were levitated and transported toward or away from the center of the spiral array, whereas at high frequencies cells were trapped at electrode edges. The frequencies of transition between these characteristic cell behaviors increased with increasing suspension conductivity. Levitation heights and radial velocities were determined simultaneously for individual cells as a function of the applied field magnitude and frequency. Results were compared with theoretical predictions from generalized dielectrophoresis theory applied in conjunction with cell dielectric parameters and simulated electric field distributions corrected for electrode polarization effects. It was shown that the conventional and traveling-wave dielectrophoretic force components dominated cell levitation and radial motion, respectively. Both theoretical predictions and experimental data showed that the cell radial velocity was very sensitive to the field frequency when the in-phase component of the field-induced polarization was close to zero. Applications of spiral electrode arrays, including the isolation of cells of clinical relevance, are discussed. Images FIGURE 1 FIGURE 3 FIGURE 4 FIGURE 11 PMID:9083692

  2. Dielectrophoretic Force Imaging of Biological Systems

    NASA Astrophysics Data System (ADS)

    Simpson, Garth J.

    2004-03-01

    A new scanning probe microscopic technique is demonstrated, exploiting AC electrokinetic forces for real-time functional imaging of biological interfaces with nanometer-scale spatial resolution. Dielectrophoresis (DEP) describes the mobility of particles in radio-frequency AC electric fields and is related to the frequency-dependent polarizability. Similar to the forces in optical trapping, DEP interactions are greatest for large field gradients, such as those adjacent to highly curved electrodes. Moderate AC potentials (5 Vpp) are more than sufficient to induce surface forces strong enough for reliable feedback during imaging. Simply changing the AC frequency can change the nature of the DEP force from repulsive to attractive. By scanning the AC frequency, dielectrophoretic spectroscopy using light with a wavelength of ˜ 1/2 km can be performed with spatial resolution of a few nanometers (about 11 to 12 orders of magnitude below the diffraction-limit), representing a new level of achievement in near-field microscopy. Among other things, the facile applicability of DEP imaging in aqueous media is ideally suited for ultrahigh resolution microscopy of biological systems, including supported lipid bilayer membranes, immobilized organelles, and living cells.

  3. Fifty years of dielectrophoretic cell separation technology.

    PubMed

    Hughes, Michael P

    2016-05-01

    In 1966, Pohl and Hawk [Science 152, 647-649 (1966)] published the first demonstration of dielectrophoresis of living and dead yeast cells; their paper described how the different ways in which the cells responded to an applied nonuniform electric field could form the basis of a cell separation method. Fifty years later, the field of dielectrophoretic (DEP) cell separation has expanded, with myriad demonstrations of its ability to sort cells on the basis of differences in electrical properties without the need for chemical labelling. As DEP separation enters its second half-century, new approaches are being found to move the technique from laboratory prototypes to functional commercial devices; to gain widespread acceptance beyond the DEP community, it will be necessary to develop ways of separating cells with throughputs, purities, and cell recovery comparable to gold-standard techniques in life sciences, such as fluorescence- and magnetically activated cell sorting. In this paper, the history of DEP separation is charted, from a description of the work leading up to the first paper, to the current dual approaches of electrode-based and electrodeless DEP separation, and the path to future acceptance outside the DEP mainstream is considered.

  4. Fifty years of dielectrophoretic cell separation technology

    PubMed Central

    Hughes, Michael P.

    2016-01-01

    In 1966, Pohl and Hawk [Science 152, 647–649 (1966)] published the first demonstration of dielectrophoresis of living and dead yeast cells; their paper described how the different ways in which the cells responded to an applied nonuniform electric field could form the basis of a cell separation method. Fifty years later, the field of dielectrophoretic (DEP) cell separation has expanded, with myriad demonstrations of its ability to sort cells on the basis of differences in electrical properties without the need for chemical labelling. As DEP separation enters its second half-century, new approaches are being found to move the technique from laboratory prototypes to functional commercial devices; to gain widespread acceptance beyond the DEP community, it will be necessary to develop ways of separating cells with throughputs, purities, and cell recovery comparable to gold-standard techniques in life sciences, such as fluorescence- and magnetically activated cell sorting. In this paper, the history of DEP separation is charted, from a description of the work leading up to the first paper, to the current dual approaches of electrode-based and electrodeless DEP separation, and the path to future acceptance outside the DEP mainstream is considered. PMID:27462377

  5. Dielectrophoretic immobilisation of antibodies on microelectrode arrays.

    PubMed

    Otto, Saskia; Kaletta, Udo; Bier, Frank F; Wenger, Christian; Hölzel, Ralph

    2014-03-07

    A silicon based chip device with a regular array of more than 100,000 cylindrical sub-microelectrodes has been developed for the dielectrophoretic (DEP) manipulation of nanoparticles and molecules in solution. It was fabricated by a standard CMOS (complementary metal oxide semiconductor) compatible process. The distribution of the electrical field gradient was calculated to predict the applicability of the setup. Heating due to field application was determined microscopically using a temperature sensitive fluorescent dye. Depending on voltage and frequency, temperature increase was found to be compatible with protein function. Successful field controlled immobilisation of biomolecules from solution was demonstrated with the autofluorescent protein R-phycoerythrin (RPE) and with fluorescently labelled IgG antibodies. Biological activity after DEP application was proven by immobilisation of an anti-RPE antibody and subsequent binding of RPE. These results demonstrate that the developed chip system allows the directed immobilisation of proteins onto microelectrodes by dielectrophoresis without the need for any chemical modification and that protein function is preserved. Being based on standard lithographical methods, further miniaturisation and on-chip integration of electronics towards a multiparameter single cell analysis system appear near at hand.

  6. Movement of particles using sequentially activated dielectrophoretic particle trapping

    DOEpatents

    Miles, Robin R.

    2004-02-03

    Manipulation of DNA and cells/spores using dielectrophoretic (DEP) forces to perform sample preparation protocols for polymerized chain reaction (PCR) based assays for various applications. This is accomplished by movement of particles using sequentially activated dielectrophoretic particle trapping. DEP forces induce a dipole in particles, and these particles can be trapped in non-uniform fields. The particles can be trapped in the high field strength region of one set of electrodes. By switching off this field and switching on an adjacent electrodes, particles can be moved down a channel with little or no flow.

  7. A novel concept of dielectrophoretic engine oil filter.

    PubMed

    Shen, Yueyang; Elele, Ezinwa; Khusid, Boris

    2011-09-01

    A novel concept of an alternating current (AC) dielectrophoretic filter with a three-dimensional electrode array is presented. A filter is constructed by winding into layers around the core tube two sheets of woven metal wire-mesh with several sheets of woven insulating wire-mesh sandwiched in between. Contrary to conventional dielectrophoretic devices, the proposed design of electrodes generates a high-gradient field over a large working volume by applying several hundred volts at a standard frequency of 60 Hz. The operating principle of filtration is based on our recently developed method of AC dielectrophoretic gating for microfluidics. The filtration efficiency is expressed in terms of two non-dimensional parameters, which describe the combined influence of the particle polarizability and size, the oil viscosity and flow rate, and the field gradient on the particle captivity. The proof-of-concept is tested by measuring the single-pass performance of two filters on positively polarized particles dispersed in engine oil: spherical glass beads, fused aluminum oxide powder, and silicon metal powder, all smaller than the mesh opening. The results obtained are used to consider the potential of using AC dielectrophoretic filtration and provide critical design guidelines for the development of a filter based on the retention capability of challenge particles.

  8. Experimental investigation on neural cell survival after dielectrophoretic trapping.

    PubMed

    Heida, T; Rutten, W L C; Marani, E

    2002-12-01

    Negative dielectrophoretic forces can effectively be used to trap cortical rat neurons. The creation of dielectrophoretic forces requires electric fields of high non-uniformity. High electric field strengths, however, can cause excessive membrane potentials by which cells may unrecoverably be changed or it may lead to cell death. In a previous study it was found that cells trapped at 3 Vtt/14 MHz did not change morphologically as compared to cells that were not exposed to the electric field. This study investigates the viability of fetal cortical rat neurons after being trapped by negative dielectrophoretic forces at frequencies up to 1 MHz. A planar quadrupole micro-electrode structure was used for the creation of a non-uniform electric field. The sinusoidal input signal was varied in amplitude (3 and 5 Vtt) and frequency (10 kHz-1 MHz). The results presented in this paper show that the viability of dielectrophoretically trapped postnatal cortical rat cells was greatly frequency dependent. To preserve viability frequencies above 100 kHz (at 3 Vtt) or 1 MHz (5 Vtt) must be used.

  9. Sedimentation field flow fractionation monitoring of rice starch amylolysis.

    PubMed

    Morelon, X; Battu, S; Salesse, C; Begaud-Grimaud, G; Cledat, D; Cardot, P J P

    2005-11-04

    Enzymatic starch granule hydrolysis is one of the most important reactions in many industrial processes. In this work, we investigated the capacity of SdFFF to monitor the native rice starch amylolysis. In order to determine if fractogram changes observed were correlated to granule biophysical modifications which occurred during amylolysis, SdFFF separation was associated with particle size distribution analysis. The results showed that SdFFF is an effective tool to monitor amylolysis of native rice starch. SdFFF analysis was a rapid (less than 10 min), simple and specific method to follow biophysical modifications of starch granules. These results suggested many different applications such as testing series of enzymes and starches. By using sub-population sorting, SdFFF could be also used to better understand starch hydrolysis mechanisms or starch granule structure.

  10. Dielectrophoretic Stretching of DNA Tethered to a Fiber Tip

    PubMed Central

    Hyun, Changbae; Kaur, Harpreet; McNabb, David S.; Li, Jiali

    2015-01-01

    In this work, we studied the stretching of λ phage DNA molecules immobilized on an optical fiber tip attached to a force sensitive tuning fork under AC electric fields. We designed a two electrodes stretching system in a small chamber: one is a gold-coated optical fiber tip electrode, and the other is a gold-coated flat electrode. By applying a dielectrophoretic force, the immobilized λ DNA molecules on the tip are stretched and the stretching process is monitored by a fluorescent microscope. The DNA stretching in three-dimensional space is optimized by varying electrode shape, electrode gap distance, AC frequency, and solution conductivity. By observing the vibrational amplitude change of a quartz tuning fork, we measured the effects due to Joule heating and the dielectrophoretic force on the tethered DNA molecules in solution. This work demonstrates a method to manipulate and characterize immobilized λ DNA molecules on a probe tip for further study of single DNA molecules. PMID:25741602

  11. A travelling wave dielectrophoretic pump for blood delivery.

    PubMed

    Lei, U; Huang, C W; Chen, James; Yang, C Y; Lo, Y J; Wo, Andrew; Chen, C F; Fung, T W

    2009-05-21

    The travelling wave dielectrophoretic pump studied here is essentially a rectangular straight micro-channel with an electrode array on part of its wall, and operated under an ac voltage with phase shift at neighbouring electrodes. The travelling wave dielectrophoretic force drives the cells, which drag the plasma, and after some sophisticated interaction between conventional dielectrophoresis, travelling wave dielectrophoresis and fluid mechanics, the whole blood is delivered. The pump was fabricated using MEMS techniques and studied in details for different parameters. It is found that the pumping velocity is maximized at an intermediate frequency around 20-30 MHz (varies with phase shift), and at an intermediate channel height at about 40 microm. The quasi-static average cell velocity can reach 15 microm s(-1) for a pump with 1 mm length and 16 electrodes (total array length 465 microm) operated at 5 V and 20 MHz with 90 degrees phase shift.

  12. Nanofluidic devices for dielectrophoretic mobility shift assays by soft lithography

    NASA Astrophysics Data System (ADS)

    Viefhues, M.; Regtmeier, J.; Anselmetti, D.

    2012-11-01

    We report development and application of 3D structured nano-microfluidic devices that were produced via soft lithography with poly(dimethylsiloxane). The procedure does not rely on hazardous or time-consuming production steps. Here, the nanochannels were created by channel-spanning ridges that reduce the flow height of the microchannel. Several realizations of the ridge layout and nanochannel height are demonstrated, depicting the high potential of this technique. The nanochannels proved to be stable even for width-to-height aspect ratios of 873:1. Additionally, an application of these submicrometer structures is presented with a new technique of a dielectrophoretic mobility shift assay (DEMSA). The DEMSA was used to detect different DNA variants, e.g. protein-DNA-complexes, via a shift in (dielectrophoretically retarded) migration velocities within an array of nanoslits.

  13. Dielectrophoretic separation of biological samples in a 3D filtering chip

    NASA Astrophysics Data System (ADS)

    Iliescu, Ciprian; Xu, Guo Lin; Ong, Poh Lam; Leck, Kwong Joo

    2007-07-01

    A field-flow dielectrophoretic separation method in a 3D filtering chip has been developed in this work. The separation method was possible due to the special configuration of the DEP filtering chip, which has a structure similar to a classical capacitor with two parallel plate electrodes (realized by using a stainless steel mesh) and a dielectric medium (defined by a suspension of 100 µm diameter silica beads in buffer solution). The dielectrophoretic phenomenon is generated by the non-uniformities of the dielectric media, which produce a gradient of the electric field and, as a consequence, a DEP force. If a suspension medium with cells flows through the filter, the DEP force can trap these cells around the contact points between the silica beads (if the cells exhibit positive DEP) or they are repelled into the space between the beads (if the cells exhibit negative DEP). It is shown that for two different cell populations, the frequency of the electric field and permittivity of the media can be tuned in such a way that one population will exhibit positive DEP and the other one negative DEP. The population that expresses negative DEP can be easily flushed out due to the hydrodynamic force which is larger at the center point between the beads. In such a way two cell populations can be separated. The working principle was verified with both live and dead yeast cells. Best results for the separation of viable and nonviable cell populations were achieved at an applied voltage of 150 V in a frequency range between 10 kHz and 20 kHz for flow rates of 0.1 ml min-1 and 0.2 ml min-1. With a few of these devices cascaded in series, higher efficiency could be achieved. As a result, this device and the associated proposed separation method can be very useful tools for bio-pharmaceutical industries since continuous flow separation at relatively high flow rates is both time and cost saving.

  14. NOTE: Dielectrophoretic assay of bacterial resistance to antibiotics

    NASA Astrophysics Data System (ADS)

    Johari, Juliana; Hübner, Yvonne; Hull, Judith C.; Dale, Jeremy W.; Hughes, Michael P.

    2003-07-01

    The dielectrophoretic collection spectra of antibiotic-sensitive and antibiotic-resistant strains of Staphylococcus epidermidis have been determined. These indicate that in the absence of antibiotic treatment there is a strong similarity between the dielectric properties of sensitive and resistant strains, and that there is a significant difference between the sensitive strains before and after treatment with the antibiotic streptomycin after 24 h exposure. This method offers possibilities for the assessment of bacterial resistance to antibiotics.

  15. Dielectrophoretic characterization of erythrocytes: positive ABO blood types.

    PubMed

    Srivastava, Soumya K; Daggolu, Prashant R; Burgess, Shane C; Minerick, Adrienne R

    2008-12-01

    Dielectrophoretic manipulation of erythrocytes/red blood cells is investigated as a tool to identify blood type for medical diagnostic applications. Positive blood types of the ABO typing system (A+, B+, AB+ and O+) were tested and cell responses quantified. The dielectrophoretic response of each blood type was observed in a platinum electrode microdevice, delivering a field of 0.025V(pp)/microm at 1 MHz. Responses were recorded via video microscopy for 120 s and erythrocyte positions were tabulated at 20-30 s intervals. Both vertical and horizontal motions of erythrocytes were quantified via image object recognition, object tracking in MATLAB, binning into appropriate electric field contoured regions (wedges) and statistical analysis. Cells of O+ type showed relatively attenuated response to the dielectrophoretic field and were distinguished with greater than 95% confidence from all the other three blood types. AB+ cell responses differed from A+ and B+ blood types likely because AB+ erythrocytes express both the A and B glycoforms on their membrane. This research suggests that dielectrophoresis of untreated erythrocytes beyond simple dilution depends on blood type and could be used in portable blood typing devices.

  16. A novel concept of dielectrophoretic engine oil filter

    NASA Astrophysics Data System (ADS)

    Khusid, Boris; Shen, Yueyang; Elele, Ezinwa

    2011-11-01

    A novel concept of an alternating current (AC) dielectrophoretic filter with a three-dimensional electrode array is presented. A filter is constructed by winding into layers around the core tube two sheets of woven metal wire-mesh with several sheets of woven insulating wire-mesh sandwiched in between. Contrary to conventional dielectrophoretic devices, the proposed design of electrodes generates a high-gradient field over a large working volume by applying several hundred volts at a standard frequency of 60 Hz. The operating principle of filtration is based on our recently developed method of AC dielectrophoretic gating for microfluidics. The filtration efficiency is expressed in terms of two non-dimensional parameters which describe the combined influence of the particle polarizability and size, the oil viscosity and flow rate, and the field gradient on the particle captivity. The proof-of-concept is tested by measuring the single-pass performance of two filters on positively polarized particles dispersed in engine oil: spherical glass beads, fused aluminum oxide powder, and silicon metal powder, all smaller than the mesh opening. The results obtained provide critical design guidelines for the development of a filter based on the retention capability of challenge particles. The work was supported in part by ONR and NSF.

  17. Characterization of Gd loaded chitosan-TPP nanohydrogels by a multi-technique approach combining dynamic light scattering (DLS), asymetrical flow-field-flow-fractionation (AF4) and atomic force microscopy (AFM) and design of positive contrast agents for molecular resonance imaging (MRI)

    NASA Astrophysics Data System (ADS)

    Rigaux, G.; Gheran, C. V.; Callewaert, M.; Cadiou, C.; Voicu, S. N.; Dinischiotu, A.; Andry, M. C.; Vander Elst, L.; Laurent, S.; Muller, R. N.; Berquand, A.; Molinari, M.; Huclier-Markai, S.; Chuburu, F.

    2017-02-01

    Chitosan CS—tripolyphosphate TPP/hyaluronic acid HA nanohydrogels loaded with gadolinium chelates (GdDOTA ⊂ CS-TPP/HA NGs) synthesized by ionic gelation were designed for lymph node (LN) MRI. In order to be efficiently drained to LNs, nanogels (NGs) needed to exhibit a diameter ϕ < 100 nm. For that, formulation parameters were tuned, using (i) CS of two different molecular weights (51 and 37 kDa) and (ii) variable CS/TPP ratio (2 < CS/TPP < 8). Characterization of NG size distribution by dynamic light scattering (DLS) and asymetrical flow-field-flow-fractionation (AF4) showed discrepancies since DLS diameters were consistently above 200 nm while AF4 showed individual nano-objects with ϕ < 100 nm. Such a difference could be correlated to the presence of aggregates inherent to ionic gelation. This point was clarified by atomic force microscopy (AFM) in liquid mode which highlighted the main presence of individual nano-objects in nanosuspensions. Thus, combination of DLS, AF4 and AFM provided a more precise characterization of GdDOTA ⊂ CS-TPP/HA nanohydrogels which, in turn, allowed to select formulations leading to NGs of suitable mean sizes showing good MRI efficiency and negligible toxicity.

  18. Characterization of Gd loaded chitosan-TPP nanohydrogels by a multi-technique approach combining dynamic light scattering (DLS), asymetrical flow-field-flow-fractionation (AF4) and atomic force microscopy (AFM) and design of positive contrast agents for molecular resonance imaging (MRI).

    PubMed

    Rigaux, G; Gheran, C V; Callewaert, M; Cadiou, C; Voicu, S N; Dinischiotu, A; Andry, M C; Vander Elst, L; Laurent, S; Muller, R N; Berquand, A; Molinari, M; Huclier-Markai, S; Chuburu, F

    2017-02-03

    Chitosan CS-tripolyphosphate TPP/hyaluronic acid HA nanohydrogels loaded with gadolinium chelates (GdDOTA ⊂ CS-TPP/HA NGs) synthesized by ionic gelation were designed for lymph node (LN) MRI. In order to be efficiently drained to LNs, nanogels (NGs) needed to exhibit a diameter ϕ < 100 nm. For that, formulation parameters were tuned, using (i) CS of two different molecular weights (51 and 37 kDa) and (ii) variable CS/TPP ratio (2 < CS/TPP < 8). Characterization of NG size distribution by dynamic light scattering (DLS) and asymetrical flow-field-flow-fractionation (AF4) showed discrepancies since DLS diameters were consistently above 200 nm while AF4 showed individual nano-objects with ϕ < 100 nm. Such a difference could be correlated to the presence of aggregates inherent to ionic gelation. This point was clarified by atomic force microscopy (AFM) in liquid mode which highlighted the main presence of individual nano-objects in nanosuspensions. Thus, combination of DLS, AF4 and AFM provided a more precise characterization of GdDOTA ⊂ CS-TPP/HA nanohydrogels which, in turn, allowed to select formulations leading to NGs of suitable mean sizes showing good MRI efficiency and negligible toxicity.

  19. Development of a 3D Graphene Electrode Dielectrophoretic Device

    PubMed Central

    Xie, Hongyu; Tewari, Radheshyam; Fukushima, Hiroyuki; Narendra, Jeffri; Heldt, Caryn; King, Julia; Minerick, Adrienne R.

    2014-01-01

    The design and fabrication of a novel 3D electrode microdevice using 50 µm thick graphene paper and 100 µm double sided tape is described. The protocol details the procedures to construct a versatile, reusable, multiple layer, laminated dielectrophoresis chamber. Specifically, six layers of 50 µm x 0.7 cm x 2 cm graphene paper and five layers of double sided tape were alternately stacked together, then clamped to a glass slide. Then a 700 μm diameter micro-well was drilled through the laminated structure using a computer-controlled micro drilling machine. Insulating properties of the tape layer between adjacent graphene layers were assured by resistance tests. Silver conductive epoxy connected alternate layers of graphene paper and formed stable connections between the graphene paper and external copper wire electrodes. The finished device was then clamped and sealed to a glass slide. The electric field gradient was modeled within the multi-layer device. Dielectrophoretic behaviors of 6 μm polystyrene beads were demonstrated in the 1 mm deep micro-well, with medium conductivities ranging from 0.0001 S/m to 1.3 S/m, and applied signal frequencies from 100 Hz to 10 MHz. Negative dielectrophoretic responses were observed in three dimensions over most of the conductivity-frequency space and cross-over frequency values are consistent with previously reported literature values. The device did not prevent AC electroosmosis and electrothermal flows, which occurred in the low and high frequency regions, respectively. The graphene paper utilized in this device is versatile and could subsequently function as a biosensor after dielectrophoretic characterizations are complete. PMID:24998694

  20. Development of a 3D graphene electrode dielectrophoretic device.

    PubMed

    Xie, Hongyu; Tewari, Radheshyam; Fukushima, Hiroyuki; Narendra, Jeffri; Heldt, Caryn; King, Julia; Minerick, Adrienne R

    2014-06-22

    The design and fabrication of a novel 3D electrode microdevice using 50 µm thick graphene paper and 100 µm double sided tape is described. The protocol details the procedures to construct a versatile, reusable, multiple layer, laminated dielectrophoresis chamber. Specifically, six layers of 50 µm x 0.7 cm x 2 cm graphene paper and five layers of double sided tape were alternately stacked together, then clamped to a glass slide. Then a 700 μm diameter micro-well was drilled through the laminated structure using a computer-controlled micro drilling machine. Insulating properties of the tape layer between adjacent graphene layers were assured by resistance tests. Silver conductive epoxy connected alternate layers of graphene paper and formed stable connections between the graphene paper and external copper wire electrodes. The finished device was then clamped and sealed to a glass slide. The electric field gradient was modeled within the multi-layer device. Dielectrophoretic behaviors of 6 μm polystyrene beads were demonstrated in the 1 mm deep micro-well, with medium conductivities ranging from 0.0001 S/m to 1.3 S/m, and applied signal frequencies from 100 Hz to 10 MHz. Negative dielectrophoretic responses were observed in three dimensions over most of the conductivity-frequency space and cross-over frequency values are consistent with previously reported literature values. The device did not prevent AC electroosmosis and electrothermal flows, which occurred in the low and high frequency regions, respectively. The graphene paper utilized in this device is versatile and could subsequently function as a biosensor after dielectrophoretic characterizations are complete.

  1. Microfluidic system for dielectrophoretic separation based on a trapezoidal electrode array.

    PubMed

    Choi, Sungyoung; Park, Je-Kyun

    2005-10-01

    This paper presents a novel microfluidic device for dielectrophoretic separation based on a trapezoidal electrode array (TEA). In this method, particles with different dielectric properties are separated by the device composed of the TEA for the dielectrophoretic deflection of particles under negative dielectrophoresis (DEP) and poly(dimethylsiloxane)(PDMS) microfluidic channel with a sinuous and expanded region. Polystyrene microparticles are exposed to an electric field generated from the TEA in the microfluidic channel and are dielectrophoretically focused to make all of them line up to one sidewall. When these particles arrive at the region of another TEA for dielectrophoretic separation, they are separated having different positions along the perpendicular direction to the fluid flow due to their different dielectrophoretic velocities. To evaluate the separation process and performance, both the effect of the flow rate on dielectrophoretic focusing and the influence of the number of trapezoidal electrodes on dielectrophoretic separation are investigated. Now that this method utilizes the TEA as a source of negative DEP, non-specific particle adhering to the electrode surface can be prevented; conventional separation approaches depending on the positive DEP force suffer from this problem. In addition, since various particle types are continuously separated, this method can be easily applicable to the separation and analysis of various dielectric particles with high particle recovery and selectivity.

  2. Dielectrophoretic Manipulation and Separation of Microparticles Using Microarray Dot Electrodes

    PubMed Central

    Yafouz, Bashar; Kadri, Nahrizul Adib; Ibrahim, Fatimah

    2014-01-01

    This paper introduces a dielectrophoretic system for the manipulation and separation of microparticles. The system is composed of five layers and utilizes microarray dot electrodes. We validated our system by conducting size-dependent manipulation and separation experiments on 1, 5 and 15 μm polystyrene particles. Our findings confirm the capability of the proposed device to rapidly and efficiently manipulate and separate microparticles of various dimensions, utilizing positive and negative dielectrophoresis (DEP) effects. Larger size particles were repelled and concentrated in the center of the dot by negative DEP, while the smaller sizes were attracted and collected by the edge of the dot by positive DEP. PMID:24705632

  3. Dielectrophoretic manipulation of fluorescing single-walled carbon nanotubes.

    PubMed

    Mureau, Natacha; Mendoza, Ernest; Silva, S Ravi P

    2007-05-01

    We investigate the behavior of fluorescing single-walled carbon nanotubes (SWCNTs) under dielectrophoretic conditions and demonstrate their collection with fluorescence microscopy. SWCNTs are dispersed in water with the aid of a nonionic surfactant, Triton X-100, and labeled through noncovalent binding with the dye 3,3'-dihexyloxacarbocyanine iodide (diOC(6)). The chromophore's affinity to the SWCNTs is due to pi-stacking interactions. Carbon nanotube (CNT) localization is clearly identified on the fluorescence images, showing that the nanotubes concentrate between the electrodes and align along the electric field lines.

  4. Dielectrophoretic particle-particle interaction under AC electrohydrodynamic flow conditions.

    PubMed

    Lee, Doh-Hyoung; Yu, Chengjie; Papazoglou, Elisabeth; Farouk, Bakhtier; Noh, Hongseok M

    2011-09-01

    We used the Maxwell stress tensor method to understand dielectrophoretic particle-particle interactions and applied the results to the interpretation of particle behaviors under alternating current (AC) electrohydrodynamic conditions such as AC electroosmosis (ACEO) and electrothermal flow (ETF). Distinct particle behaviors were observed under ACEO and ETF. Diverse particle-particle interactions observed in experiments such as particle clustering, particles keeping a certain distance from each other, chain and disc formation and their rotation, are explained based on the numerical simulation data. The improved understanding of particle behaviors in AC electrohydrodynamic flows presented here will enable researchers to design better particle manipulation strategies for lab-on-a-chip applications.

  5. Embryo formation from low sperm concentration by using dielectrophoretic force

    PubMed Central

    Huang, Hong-Yuan; Huang, Yu-Hsuan; Kao, Wei-Lun

    2015-01-01

    A biochip system imitates the oviduct of mammals with a microfluidic channel to achieve fertilization in vitro of imprinting-control-region (ICR) mice. We apply a method to manipulate and to position the oocyte and the sperm of ICR mice at the same time in our microfluidic channel with a positive dielectrophoretic (DEP) force. The positive dielectrophoretic response of the oocyte and sperm was exhibited under applied bias conditions AC 10 Vpp waveform, 1 MHz, 10 min. With this method, the concentration of sperm in the vicinity of the oocyte was increased and enhanced the probability of natural fertilization. We used commercial numerical software (CFDRC-ACE+) to simulate the square of the electric field and analyzed the location at which the oocyte and sperm are trapped. The microfluidic devices were designed and fabricated with poly(dimethylsiloxane). The results of our experiments indicate that a positive DEP served to drive the position of the oocyte and the sperm to natural fertilization (average rate of fertilization 51.58%) in our microchannel structures at insemination concentration 1.5 × 106 sperm ml−1. Embryos were cultured to two cells after 24 h and four cells after 48 h. PMID:25825615

  6. Dielectrophoretic behaviours of microdroplet sandwiched between LN substrates

    NASA Astrophysics Data System (ADS)

    Chen, Lipin; Li, Shaobei; Fan, Bolin; Yan, Wenbo; Wang, Donghui; Shi, Lihong; Chen, Hongjian; Ban, Dechao; Sun, Shihao

    2016-07-01

    We demonstrate a sandwich configuration for microfluidic manipulation in LiNbO3 platform based on photovoltaic effect, and the behaviours of dielectric microdroplet under this sandwich configuration are investigated. It is found that the microdroplet can generate in the form of liquid bridge inside the LiNbO3-based sandwich structure under the governing dielectrophoretic force, and the dynamic process of microdroplet generation highly depends on the substrate combinations. Dynamic features found for different combinations are explained by the different electrostatic field distribution basing on the finite-element simulation results. Moreover, the electrostatic field required by the microdroplet generation is estimated through meniscus evolution and it is found in good agreement with the simulated electrostatic field inside the sandwich gap. Several kinds of microdroplet manipulations are attempted in this work. We suggest that the local dielectrophoretic force acting on the microdroplet depends on the distribution of the accumulated irradiation dosage. Without using any additional pumping or jetting actuator, the microdroplet can be step-moved, deformed or patterned by the inconsecutive dot-irradiation scheme, as well as elastically stretched out and back or smoothly guided in a designed pass by the consecutive line-irradiation scheme.

  7. Dielectrophoretic behaviours of microdroplet sandwiched between LN substrates

    PubMed Central

    Chen, Lipin; Li, Shaobei; Fan, Bolin; Yan, Wenbo; Wang, Donghui; Shi, Lihong; Chen, Hongjian; Ban, Dechao; Sun, Shihao

    2016-01-01

    We demonstrate a sandwich configuration for microfluidic manipulation in LiNbO3 platform based on photovoltaic effect, and the behaviours of dielectric microdroplet under this sandwich configuration are investigated. It is found that the microdroplet can generate in the form of liquid bridge inside the LiNbO3-based sandwich structure under the governing dielectrophoretic force, and the dynamic process of microdroplet generation highly depends on the substrate combinations. Dynamic features found for different combinations are explained by the different electrostatic field distribution basing on the finite-element simulation results. Moreover, the electrostatic field required by the microdroplet generation is estimated through meniscus evolution and it is found in good agreement with the simulated electrostatic field inside the sandwich gap. Several kinds of microdroplet manipulations are attempted in this work. We suggest that the local dielectrophoretic force acting on the microdroplet depends on the distribution of the accumulated irradiation dosage. Without using any additional pumping or jetting actuator, the microdroplet can be step-moved, deformed or patterned by the inconsecutive dot-irradiation scheme, as well as elastically stretched out and back or smoothly guided in a designed pass by the consecutive line-irradiation scheme. PMID:27383027

  8. DNA migration and separation on surfaces with a microscale dielectrophoretic trap array.

    PubMed

    Petersen, Eric; Li, Bingquan; Fang, Xiaohua; Luo, Haobin; Samuilov, Vladimir; Gersappe, Dilip; Sokolov, Jonathan; Chu, Benjamin; Rafailovich, Miriam

    2007-02-23

    We studied the surface migration of DNA chains driven by a dc electric field across localized dielectrophoretic traps. By adjusting the length scale of the trap array, separation of a selected band of DNA was accomplished with a scaling exponent between mobility and number of base pairs similar to that obtained in capillary electrophoresis. We then provided a model, which predicts the trapping and extension of DNA chains at a dielectrophoretic trap responsible for the surface mobility and separation.

  9. Cell patterning for liver tissue engineering via dielectrophoretic mechanisms.

    PubMed

    Yahya, Wan Nurlina Wan; Kadri, Nahrizul Adib; Ibrahim, Fatimah

    2014-07-02

    Liver transplantation is the most common treatment for patients with end-stage liver failure. However, liver transplantation is greatly limited by a shortage of donors. Liver tissue engineering may offer an alternative by providing an implantable engineered liver. Currently, diverse types of engineering approaches for in vitro liver cell culture are available, including scaffold-based methods, microfluidic platforms, and micropatterning techniques. Active cell patterning via dielectrophoretic (DEP) force showed some advantages over other methods, including high speed, ease of handling, high precision and being label-free. This article summarizes liver function and regenerative mechanisms for better understanding in developing engineered liver. We then review recent advances in liver tissue engineering techniques and focus on DEP-based cell patterning, including microelectrode design and patterning configuration.

  10. Dielectrophoretic manipulation of particles for use in microfluidic devices

    SciTech Connect

    Belgrader, P; Bettencourt, K; Hamilton, J; Miles, R; Nasarabadi, S

    1999-06-23

    Amplification and hybridization of DNA are commonly used techniques to verify the presence of a specific DNA sequence in a test sample. Automatic sample handling to concentrate and purify sample prior to amplification is desirable both from the cost standpoint and from the standpoint of reducing the possibility of sample contamination. This paper explores the use of the dielectrophoretic force to manipulate DNA, Bacillus globigii spores, and Erwinia herbicola bacteria to provide concentration and purification as part of the sample handling functions in biological monitoring equipment. It was found that for what would be considered a typical microfabricated structure with electrode gaps at 30 {micro}m operating at 5V, that concentration of the particles is very effective.

  11. Dielectrophoretic manipulation of the mixture of isotropic and nematic liquid

    NASA Astrophysics Data System (ADS)

    Kim, Soo-Dong; Lee, Bomi; Kang, Shin-Woong; Song, Jang-Kun

    2015-08-01

    In various applications involving liquid crystals, the manipulation of the nanoscale molecular assembly and microscale director alignment is highly useful. Here we show that a nematic-isotropic mixture, a unique bi-liquid system, has potential for the fabrication of microstructures having an ordered phase within a disordered phase, or vice versa. The volume expansion and shrinkage, migration, splitting, mergence and elongation of one phase within the other are easily accomplished via thermal treatment and dielectrophoretic manipulation. This is particularly achievable when one phase is suspended in the middle. In that case, a highly biased ordered-phase preference of surfaces, that is, the nematic-philic nature of a polyimide layer and the nematic-phobic nature of a self-assembled monolayer of chlorosilane derivatives, is used. Further, by combining this approach with photopolymerization, the patterned microstructure is solidified as a patterned polymer film having both isotropic and anisotropic molecular arrangements simultaneously, or as a template with a morphological variation.

  12. Cell Patterning for Liver Tissue Engineering via Dielectrophoretic Mechanisms

    PubMed Central

    Yahya, Wan Nurlina Wan; Kadri, Nahrizul Adib; Ibrahim, Fatimah

    2014-01-01

    Liver transplantation is the most common treatment for patients with end-stage liver failure. However, liver transplantation is greatly limited by a shortage of donors. Liver tissue engineering may offer an alternative by providing an implantable engineered liver. Currently, diverse types of engineering approaches for in vitro liver cell culture are available, including scaffold-based methods, microfluidic platforms, and micropatterning techniques. Active cell patterning via dielectrophoretic (DEP) force showed some advantages over other methods, including high speed, ease of handling, high precision and being label-free. This article summarizes liver function and regenerative mechanisms for better understanding in developing engineered liver. We then review recent advances in liver tissue engineering techniques and focus on DEP-based cell patterning, including microelectrode design and patterning configuration. PMID:24991941

  13. Dielectrophoretic capture of low abundance cell population using thick electrodes

    PubMed Central

    Marchalot, Julien; Chateaux, Jean-François; Faivre, Magalie; Mertani, Hichem C.; Ferrigno, Rosaria; Deman, Anne-Laure

    2015-01-01

    Enrichment of rare cell populations such as Circulating Tumor Cells (CTCs) is a critical step before performing analysis. This paper presents a polymeric microfluidic device with integrated thick Carbon-PolyDimethylSiloxane composite (C-PDMS) electrodes designed to carry out dielectrophoretic (DEP) trapping of low abundance biological cells. Such conductive composite material presents advantages over metallic structures. Indeed, as it combines properties of both the matrix and doping particles, C-PDMS allows the easy and fast integration of conductive microstructures using a soft-lithography approach while preserving O2 plasma bonding properties of PDMS substrate and avoiding a cumbersome alignment procedure. Here, we first performed numerical simulations to demonstrate the advantage of such thick C-PDMS electrodes over a coplanar electrode configuration. It is well established that dielectrophoretic force (FDEP) decreases quickly as the distance from the electrode surface increases resulting in coplanar configuration to a low trapping efficiency at high flow rate. Here, we showed quantitatively that by using electrodes as thick as a microchannel height, it is possible to extend the DEP force influence in the whole volume of the channel compared to coplanar electrode configuration and maintaining high trapping efficiency while increasing the throughput. This model was then used to numerically optimize a thick C-PDMS electrode configuration in terms of trapping efficiency. Then, optimized microfluidic configurations were fabricated and tested at various flow rates for the trapping of MDA-MB-231 breast cancer cell line. We reached trapping efficiencies of 97% at 20 μl/h and 78.7% at 80 μl/h, for 100 μm thick electrodes. Finally, we applied our device to the separation and localized trapping of CTCs (MDA-MB-231) from a red blood cells sample (concentration ratio of 1:10). PMID:26392836

  14. Direct current insulator-based dielectrophoretic characterization of erythrocytes: ABO-Rh human blood typing.

    PubMed

    Srivastava, Soumya K; Artemiou, Andreas; Minerick, Adrienne R

    2011-09-01

    A microfluidic platform developed for quantifying the dependence of erythrocyte (red blood cell, RBC) responses by ABO-Rh blood type via direct current insulator dielectrophoresis (DC-iDEP) is presented. The PDMS DC-iDEP device utilized a 400 x 170 μm² rectangular insulating obstacle embedded in a 1.46-cm long, 200-μm wide inlet channel to create spatial non-uniformities in direct current (DC) electric field density realized by separation into four outlet channels. The DC-iDEP flow behaviors were investigated for all eight blood types (A+, A-, B+, B-, AB+, AB-, O+, O-) in the human ABO-Rh blood typing system. Three independent donors of each blood type, same donor reproducibility, different conductivity buffers (0.52-9.1 mS/cm), and DC electric fields (17.1-68.5 V/cm) were tested to investigate separation dependencies. The data analysis was conducted from image intensity profiles across inlet and outlet channels in the device. Individual channel fractions suggest that the dielectrophoretic force experienced by the cells is dependent on erythrocyte antigen expression. Two different statistical analysis methods were conducted to determine how distinguishable a single blood type was from the others. Results indicate that channel fraction distributions differ by ABO-Rh blood types suggesting that antigens present on the erythrocyte membrane polarize differently in DC-iDEP fields. Under optimized conductivity and field conditions, certain blind blood samples could be sorted with low misclassification rates.

  15. Fourier-bessel series modeling of dielectrophoretic bionanoparticle transport: principles and applications.

    PubMed

    Bakewell, David J; Chichenkov, Aleksandr

    2012-03-01

    Principles and applications are described for a Fourier-Bessel series model that predicts the transport of bionanoparticles driven by a dielectrophoretic (DEP) force and randomized by Brownian motion. The model is applicable for a dielectrophoretic force that spatially decays from the electrode array according to a reciprocal-law; that is, in the near field of a planar interdigitated array or in the far field where other long range forces assist DEP transport, e.g., ac electro-osmosis. Capabilities of the model are demonstrated for estimating and decomposing data typical of dielectrophoretic bionanoparticle collection experiments. An important approximation, for moderately strong DEP forces, is that a collection can largely be described by a single exponential profile with a square-law dependence on microdevice chamber height. Applications of the model demonstrate transformation and representation of time-dependent bionanoparticle transport in the frequency domain and prediction of a modulation bandwidth that concurs with experimental observations.

  16. Dielectrophoretic Rayleigh-Bénard convection under microgravity conditions.

    PubMed

    Yoshikawa, H N; Tadie Fogaing, M; Crumeyrolle, O; Mutabazi, I

    2013-04-01

    Thermal convection in a dielectric fluid layer between two parallel plates subjected to an alternating electric field and a temperature gradient is investigated under microgravity conditions. A thermoelectric coupling resulting from the thermal variation of the electric permittivity of the fluid produces the dielectrophoretic (DEP) body force, which can be regarded as thermal buoyancy due to an effective gravity. This electric gravity can destabilize a stationary conductive state of the fluid to develop convection. The similarity of the DEP thermal convection with the Rayleigh-Bénard (RB) convection is examined by considering its behavior in detail by a linear stability theory and a two-dimensional direct numerical simulation. The results are analyzed from an energetic viewpoint and in the framework of the Ginzburg-Landau (GL) equation. The stabilizing effects of a thermoelectric feedback make the critical parameters different from those in the RB instability. The nonuniformity of the electric gravity arising from the finite variation of permittivity also affects the critical parameters. The characteristic constants of the GL equation are comparable with those for the RB convection. The heat transfer in the DEP convection is weaker than in the RB convection as a consequence of the feedback that impedes the convection.

  17. Nanotip analysis for dielectrophoretic concentration of nanosized viral particles.

    PubMed

    Yeo, Woon-Hong; Lee, Hyun-Boo; Kim, Jong-Hoon; Lee, Kyong-Hoon; Chung, Jae-Hyun

    2013-05-10

    Rapid and sensitive detection of low-abundance viral particles is strongly demanded in health care, environmental control, military defense, and homeland security. Current detection methods, however, lack either assay speed or sensitivity, mainly due to the nanosized viral particles. In this paper, we compare a dendritic, multi-terminal nanotip ('dendritic nanotip') with a single terminal nanotip ('single nanotip') for dielectrophoretic (DEP) concentration of viral particles. The numerical computation studies the concentration efficiency of viral particles ranging from 25 to 100 nm in radius for both nanotips. With DEP and Brownian motion considered, when the particle radius decreases by two times, the concentration time for both nanotips increases by 4-5 times. In the computational study, a dendritic nanotip shows about 1.5 times faster concentration than a single nanotip for the viral particles because the dendritic structure increases the DEP-effective area to overcome the Brownian motion. For the qualitative support of the numerical results, the comparison experiment of a dendritic nanotip and a single nanotip is conducted. Under 1 min of concentration time, a dendritic nanotip shows a higher sensitivity than a single nanotip. When the concentration time is 5 min, the sensitivity of a dendritic nanotip for T7 phage is 10(4) particles ml(-1). The dendritic nanotip-based concentrator has the potential for rapid identification of viral particles.

  18. Nano plasmon device fabrications using dielectrophoretic (DEP) force

    NASA Astrophysics Data System (ADS)

    Kim, J.; Kang, C.-M.; Kim, S.; Suh, J.-k. F.; Shin, H. J.; Park, J. H.

    2013-09-01

    We propose a fabrication process using dielectrophoretic (DEP) force for plasmonic devices as a light source. The 100nm wide Au nanowires fabricated by e-beam lithography and lift-off were used to trap 25nm diameter cadmium selenide (CdSe) QDs on its end-facet with DEP force. DEP force was induced around the nanowire using 8 Vpp, 3MHz sine wave. An Electric field of 108 V/m order and electric field gradient of 1015 V/m2 order intensity were calculated with COMSOL multiphysics simulation tool. And the values are enough to induce DEP force for QD trapping. Before the QD manipulations, polystyrene bead was used which is more rigid and influenced by DEP force than QD. Concentration of 10-5% order and approximately 120sec reaction time are considered with polystyrene bead and QD manipulations are accomplished with the conditions. Finally, the QDs were manipulated to the nanowires array and `QD on nanowire' nanostructure was formed as a practical plasmonic device using DEP force.

  19. Nanotip analysis for dielectrophoretic concentration of nanosized viral particles

    NASA Astrophysics Data System (ADS)

    Yeo, Woon-Hong; Lee, Hyun-Boo; Kim, Jong-Hoon; Lee, Kyong-Hoon; Chung, Jae-Hyun

    2013-05-01

    Rapid and sensitive detection of low-abundance viral particles is strongly demanded in health care, environmental control, military defense, and homeland security. Current detection methods, however, lack either assay speed or sensitivity, mainly due to the nanosized viral particles. In this paper, we compare a dendritic, multi-terminal nanotip (‘dendritic nanotip’) with a single terminal nanotip (‘single nanotip’) for dielectrophoretic (DEP) concentration of viral particles. The numerical computation studies the concentration efficiency of viral particles ranging from 25 to 100 nm in radius for both nanotips. With DEP and Brownian motion considered, when the particle radius decreases by two times, the concentration time for both nanotips increases by 4-5 times. In the computational study, a dendritic nanotip shows about 1.5 times faster concentration than a single nanotip for the viral particles because the dendritic structure increases the DEP-effective area to overcome the Brownian motion. For the qualitative support of the numerical results, the comparison experiment of a dendritic nanotip and a single nanotip is conducted. Under 1 min of concentration time, a dendritic nanotip shows a higher sensitivity than a single nanotip. When the concentration time is 5 min, the sensitivity of a dendritic nanotip for T7 phage is 104 particles ml-1. The dendritic nanotip-based concentrator has the potential for rapid identification of viral particles.

  20. Dielectrophoretic characterization of antibiotic-treated Mycobacterium tuberculosis complex cells.

    PubMed

    Inoue, Shinnosuke; Lee, Hyun-Boo; Becker, Annie L; Weigel, Kris M; Kim, Jong-Hoon; Lee, Kyong-Hoon; Cangelosi, Gerard A; Chung, Jae-Hyun

    2015-10-01

    Multi-drug resistant tuberculosis (MDR-TB) has become a serious concern for proper treatment of patients. As a phenotypic method, dielectrophoresis can be useful but is yet to be attempted to evaluate Mycobacterium tuberculosis complex cells. This paper investigates the dielectrophoretic behavior of Mycobacterium bovis (Bacillus Calmette-Guérin, BCG) cells that are treated with heat or antibiotics rifampin (RIF) or isoniazid (INH). The experimental parameters are designed on the basis of our sensitivity analysis. The medium conductivity (σ(m)) and the frequency (f) for a crossover frequency (f(xo1)) test are decided to detect the change of σ(m)-f(xo1) in conjunction with the drug mechanism. Statistical modeling is conducted to estimate the distributions of viable and nonviable cells from the discrete measurement of f (xo1). Finally, the parameters of the electrophysiology of BCG cells, C(envelope) and σ(cyto), are extracted through a sampling algorithm. This is the first evaluation of the dielectrophoresis (DEP) approach as a means to assess the effects of antimicrobial drugs on M. tuberculosis complex cells.

  1. Electrophoretic Versus Dielectrophoretic Nanoparticle Patterning Using Optoelectronic Tweezers

    NASA Astrophysics Data System (ADS)

    Muñoz-Martínez, Juan F.; Ramiro, José B.; Alcázar, Ángel; García-Cabañes, Ángel; Carrascosa, Mercedes

    2017-06-01

    Currently, there is increasing interest from many scientific disciplines in the development of systems that are able to sort and arrange many objects in parallel at the nano- and micrometric scale. Among others, photovoltaic tweezers (PVT) are an optoelectronic technique for trapping and patterning nano- and micro-objects in accordance with an arbitrary light profile. In this work, the differential features of electro- and dielectrophoretic (EP and DEP) nanoparticle (NP) patterning using PVT are deeply investigated. The study is carried out through theory and experiments. The developed theory extends the applicability of a previously reported model to be able to compute EP potentials and to obtain numerical values for the EP and DEP potential energies. Two-dimensional patterns of charged and neutral aluminum NPs are fabricated on top of Fe ∶LiNbO3 crystals, and different light distributions and other experimental parameters (crystal thickness and NP concentration) are compared. Patterns of charged and neutral NPs show remarkable differences in both particle density distribution and fidelity to the original light profile. The observed different features between EP and DEP trapping are satisfactorily explained by the theoretical analysis. The results provide routes for the optimization of the NP arrangements for both regimes.

  2. Isolation of prostate tumor initiating cells (TICs) through their dielectrophoretic signature.

    PubMed

    Salmanzadeh, Alireza; Romero, Lina; Shafiee, Hadi; Gallo-Villanueva, Roberto C; Stremler, Mark A; Cramer, Scott D; Davalos, Rafael V

    2012-01-07

    In this study, the dielectrophoretic response of prostate tumor initiating cells (TICs) was investigated in a microfluidic system utilizing contactless dielectrophoresis (cDEP). The dielectrophoretic response of prostate TICs was observed to be distinctively different than that for non-TICs, enabling them to be sorted using cDEP. Culturing the sorted TICs generated spheroids, indicating that they were indeed initiating cells. This study presents the first marker-free TIC separation from non-TICs utilizing their electrical fingerprints through dielectrophoresis.

  3. Dielectrophoretic Capture and Genetic Analysis of Single Neuroblastoma Tumor Cells

    PubMed Central

    Carpenter, Erica L.; Rader, JulieAnn; Ruden, Jacob; Rappaport, Eric F.; Hunter, Kristen N.; Hallberg, Paul L.; Krytska, Kate; O’Dwyer, Peter J.; Mosse, Yael P.

    2014-01-01

    Our understanding of the diversity of cells that escape the primary tumor and seed micrometastases remains rudimentary, and approaches for studying circulating and disseminated tumor cells have been limited by low throughput and sensitivity, reliance on single parameter sorting, and a focus on enumeration rather than phenotypic and genetic characterization. Here, we utilize a highly sensitive microfluidic and dielectrophoretic approach for the isolation and genetic analysis of individual tumor cells. We employed fluorescence labeling to isolate 208 single cells from spiking experiments conducted with 11 cell lines, including 8 neuroblastoma cell lines, and achieved a capture sensitivity of 1 tumor cell per 106 white blood cells (WBCs). Sample fixation or freezing had no detectable effect on cell capture. Point mutations were accurately detected in the whole genome amplification product of captured single tumor cells but not in negative control WBCs. We applied this approach to capture 144 single tumor cells from 10 bone marrow samples of patients suffering from neuroblastoma. In this pediatric malignancy, high-risk patients often exhibit wide-spread hematogenous metastasis, but access to primary tumor can be difficult or impossible. Here, we used flow-based sorting to pre-enrich samples with tumor involvement below 0.02%. For all patients for whom a mutation in the Anaplastic Lymphoma Kinase gene had already been detected in their primary tumor, the same mutation was detected in single cells from their marrow. These findings demonstrate a novel, non-invasive, and adaptable method for the capture and genetic analysis of single tumor cells from cancer patients. PMID:25133137

  4. A continuous DC-insulator dielectrophoretic sorter of microparticles.

    PubMed

    Srivastava, Soumya Keshavamurthy; Baylon-Cardiel, Javier L; Lapizco-Encinas, Blanca H; Minerick, Adrienne Robyn

    2011-04-01

    A lab-on-a-chip device is described for continuous sorting of fluorescent polystyrene microparticles utilizing direct current insulating dielectrophoresis (DC-iDEP) at lower voltages than previously reported. Particles were sorted by combining electrokinetics and dielectrophoresis in a 250 μm wide PDMS microchannel containing a rectangular insulating obstacle and four outlet channels. The DC-iDEP particle flow behaviors were investigated with 3.18, 6.20 and 10 μm fluorescent polystyrene particles which experience negative DEP forces depending on particle size, DC electric field magnitude and medium conductivity. Due to negative DEP effects, particles are deflected into different outlet streams as they pass the region of high electric field density around the obstacle. Particles suspended in dextrose added phosphate buffer saline (PBS) at conductivities ranging from 0.50 to 8.50 mS/cm at pH 7.0 were compared at 6.85 and 17.1V/cm. Simulations of electrokinetic and dielectrophoretic forces were conducted with COMSOL Multiphysics® to predict particle pathlines. Experimental and simulation results show the effect of medium and voltage operating conditions on particle sorting. Further, smaller particles experience smaller iDEP forces and are more susceptible to competing nonlinear electrostatic effects, whereas larger particles experience greater iDEP forces and prefer channels 1 and 2. This work demonstrates that 6.20 and 10 μm particles can be independently sorted into specific outlet streams by tuning medium conductivity even at low operating voltages. This work is an essential step forward in employing DC-iDEP for multiparticle sorting in a continuous flow, multiple outlet lab-on-a-chip device.

  5. Label-free electrical quantification of the dielectrophoretic response of DNA

    PubMed Central

    Henning, Anja; Henkel, Jörg; Bier, Frank F; Hölzel, Ralph

    2008-01-01

    A purely electrical sensing scheme is presented that determines the concentration of macromolecules in solution by measuring the capacitance between planar microelectrodes. Concentrations of DNA in the ng/mL range have been used in samples of 1 μL volume. The method has been applied to the characterisation of the dielectrophoretic response of DNA without the need for any chemical modifications. The influence of electrical parameters like duty cycle, voltage and frequency has been investigated. The results are in good agreement with data from dielectrophoretic studies on fluorescently labelled DNA. Extension of the method down to the single molecule level appears feasible. PACS: 87.50.ch, 87.80.Fe, 87.85.fK PMID:19351426

  6. Joule heating effects on particle immobilization in insulator-based dielectrophoretic devices

    PubMed Central

    Gallo-Villanueva, Roberto C.; Sano, Michael B.; Lapizco-Encinas, Blanca H.; Davalos, Rafael V.

    2014-01-01

    In this work, the temperature effects due to Joule heating obtained by application of a DC electric potential were investigated for a microchannel with cylindrical insulating posts employed for insulator based dielectrophoresis (iDEP). The conductivity of the suspending medium, the local electric field, and the gradient of the squared electric field, which directly affect the magnitude of the dielectrophoretic force exerted on particles, were computationally simulated employing COMSOL Multiphysics. It was observed that a temperature gradient is formed along the microchannel which redistributes the conductivity of the suspending medium leading to an increase of the dielectrophoretic force towards the inlet of the channel while decreasing towards the outlet. Experimental results are in good agreement with simulations on the particle trapping zones anticipated. This study demonstrates the importance of considering Joule heating effects when designing iDEP systems. PMID:24002905

  7. Joule heating effects on particle immobilization in insulator-based dielectrophoretic devices.

    PubMed

    Gallo-Villanueva, Roberto C; Sano, Michael B; Lapizco-Encinas, Blanca H; Davalos, Rafael V

    2014-02-01

    In this work, the temperature effects due to Joule heating obtained by application of a direct current electric potential were investigated for a microchannel with cylindrical insulating posts employed for insulator-based dielectrophoresis. The conductivity of the suspending medium, the local electric field, and the gradient of the squared electric field, which directly affect the magnitude of the dielectrophoretic force exerted on particles, were computationally simulated employing COMSOL Multiphysics. It was observed that a temperature gradient is formed along the microchannel, which redistributes the conductivity of the suspending medium leading to an increase of the dielectrophoretic force toward the inlet of the channel while decreasing toward the outlet. Experimental results are in good agreement with simulations on the particle-trapping zones anticipated. This study demonstrates the importance of considering Joule heating effects when designing insulator-based dielectrophoresis systems.

  8. Effect of surface charge convection and shape deformation on the dielectrophoretic motion of a liquid drop

    NASA Astrophysics Data System (ADS)

    Mandal, Shubhadeep; Bandopadhyay, Aditya; Chakraborty, Suman

    2016-04-01

    The dielectrophoretic motion and shape deformation of a Newtonian liquid drop in an otherwise quiescent Newtonian liquid medium in the presence of an axisymmetric nonuniform dc electric field consisting of uniform and quadrupole components is investigated. The theory put forward by Feng [J. Q. Feng, Phys. Rev. E 54, 4438 (1996), 10.1103/PhysRevE.54.4438] is generalized by incorporating the following two nonlinear effects—surface charge convection and shape deformation—towards determining the drop velocity. This two-way coupled moving boundary problem is solved analytically by considering small values of electric Reynolds number (ratio of charge relaxation time scale to the convection time scale) and electric capillary number (ratio of electrical stress to the surface tension) under the framework of the leaky dielectric model. We focus on investigating the effects of charge convection and shape deformation for different drop-medium combinations. A perfectly conducting drop suspended in a leaky (or perfectly) dielectric medium always deforms to a prolate shape and this kind of shape deformation always augments the dielectrophoretic drop velocity. For a perfectly dielectric drop suspended in a perfectly dielectric medium, the shape deformation leads to either increase (for prolate shape) or decrease (for oblate shape) in the dielectrophoretic drop velocity. Both surface charge convection and shape deformation affect the drop motion for leaky dielectric drops. The combined effect of these can significantly increase or decrease the dielectrophoretic drop velocity depending on the electrohydrodynamic properties of both the liquids and the relative strength of the electric Reynolds number and electric capillary number. Finally, comparison with the existing experiments reveals better agreement with the present theory.

  9. Particle Removal by Electrostatic and Dielectrophoretic Forces for Dust Control During Lunar Exploration Missions

    NASA Technical Reports Server (NTRS)

    Calle, C. I.; Buhler, C. R.; McFall, J. L.; Snyder, S. J.

    2009-01-01

    Particle removal during lunar exploration activities is of prime importance for the success of robotic and human exploration of the moon. We report on our efforts to use electrostatic and dielectrophoretic forces to develop a dust removal technology that prevents the accumulation of dust on solar panels and removes dust adhering to those surfaces. Testing of several prototypes showed solar shield output above 90% of the initial potentials after dust clearing.

  10. Dielectrophoretic differentiation of mouse ovarian surface epithelial cells, macrophages, and fibroblasts using contactless dielectrophoresis

    PubMed Central

    Salmanzadeh, Alireza; Kittur, Harsha; Sano, Michael B.; C. Roberts, Paul; Schmelz, Eva M.; Davalos, Rafael V.

    2012-01-01

    Ovarian cancer is the leading cause of death from gynecological malignancies in women. The primary challenge is the detection of the cancer at an early stage, since this drastically increases the survival rate. In this study we investigated the dielectrophoretic responses of progressive stages of mouse ovarian surface epithelial (MOSE) cells, as well as mouse fibroblast and macrophage cell lines, utilizing contactless dielectrophoresis (cDEP). cDEP is a relatively new cell manipulation technique that has addressed some of the challenges of conventional dielectrophoretic methods. To evaluate our microfluidic device performance, we computationally studied the effects of altering various geometrical parameters, such as the size and arrangement of insulating structures, on dielectrophoretic and drag forces. We found that the trapping voltage of MOSE cells increases as the cells progress from a non-tumorigenic, benign cell to a tumorigenic, malignant phenotype. Additionally, all MOSE cells display unique behavior compared to fibroblasts and macrophages, representing normal and inflammatory cells found in the peritoneal fluid. Based on these findings, we predict that cDEP can be utilized for isolation of ovarian cancer cells from peritoneal fluid as an early cancer detection tool. PMID:22536308

  11. Polarizability of Six-Helix Bundle and Triangle DNA Origami and Their Escape Characteristics from a Dielectrophoretic Trap.

    PubMed

    Gan, Lin; Camacho-Alanis, Fernanda; Ros, Alexandra

    2015-12-15

    DNA nanoassemblies, such as DNA origamis, hold promise in biosensing, drug delivery, nanoelectronic circuits, and biological computing, which require suitable methods for migration and precision positioning. Insulator-based dielectrophoresis (iDEP) has been demonstrated as a powerful migration and trapping tool for μm- and nm-sized colloids as well as DNA origamis. However, little is known about the polarizability of origami species, which is responsible for their dielectrophoretic migration. Here, we report the experimentally determined polarizabilities of the six-helix bundle origami (6HxB) and triangle origami by measuring the migration times through a potential landscape exhibiting dielectrophoretic barriers. The resulting migration times correlate to the depth of the dielectrophoretic potential barrier and the escape characteristics of the origami according to an adapted Kramer's rate model, allowing their polarizabilities to be determined. We found that the 6HxB polarizability is larger than that of the triangle origami, which correlates with the variations in charge density of both origamis. Further, we discuss the orientation of both origami species in the dielectrophoretic trap and discuss the influence of diffusion during the escape process. Our study provides detailed insight into the factors contributing to the migration through dielectrophoretic potential landscapes, which can be exploited for applications with DNA and other nanoassemblies based on dielectrophoresis.

  12. Quantitative characterization for dielectrophoretic behavior of biological cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Park, In Soo; Hee Park, Se; Woo Lee, Sang; Sung Yoon, Dae; Kim, Beop-Min

    2014-02-01

    We report a method to precisely quantify dielectrophoretic (DEP) forces and cutoff frequencies (fc) of viable and nonviable yeast cells. The method consists of a two-step process in which generated DEP forces act upon a cell through a micro-electrode device, followed by direct measurement of DEP forces using optical tweezers. DEP behaviors of viable and nonviable yeast cells are monitored as a function of AC frequency. We believe that the proposed method can be used as a powerful platform for cell-based assays to characterize the DEP behavior of various cell types including cancer and normal cells.

  13. Biomolecule detection via target mediated nanoparticle aggregation and dielectrophoretic impedance measurement.

    PubMed

    Costanzo, Philip J; Liang, Enzhu; Patten, Timothy E; Collins, Scott D; Smith, Rosemary L

    2005-06-01

    A new biosensing system is described that is based on the aggregation of nanoparticles by a target biological molecule and dielectrophoretic impedance measurement of these aggregates. The aggregation process was verified within a microchannel via fluorescence microscopy, demonstrating that this process can be used in a real time sensor application. Positive dielectrophoresis is employed to capture the nanoparticle aggregates at the edge of thin film electrodes, where their presence is detected either by optical imaging via fluorescence microscopy or by measuring the change in electrical impedance between adjacent electrodes. The electrical detection mechanism demonstrates the potential for this method as a micro total analysis system (microTAS).

  14. A low cost solution for the fabrication of dielectrophoretic microfluidic devices and embedded electrodes.

    PubMed

    Sano, Michael B; Caldwell, John L; Davalos, Rafael V

    2011-01-01

    The versatility of a simple method for producing microfluidic devices with embedded electrodes is demonstrated through the fabrication and operation of two dielectrophoretic devices; one employing interdigitated electrode structures on glass and the other employing contactless electrode reservoirs. Device manufacture is based on the precipitation of silver and subsequent photolithography of thin film resists conducted outside of a cleanroom environment. In current experiments, minimum channel widths of 50 microns and electrode widths of 25 microns are achieved when the distance between features is 40 microns or greater. These results illustrate this technique's potential to produce microfluidic devices with embedded electrodes for lab on chip applications while significantly reducing fabrication expense.

  15. Gravitational Effects on Near-Field Flow Structure of Low-Density Gas Jets

    NASA Technical Reports Server (NTRS)

    Yep, Tze-Wing; Agrawal, Ajay K.; Griffin, DeVon

    2004-01-01

    Experiments were conducted in earth gravity and micro gravity to acquire quantitative data on near field flow structure of helium jets injected into air. Microgravity conditions were simulated in the 2.2 s drop tower at NASA John H. Glenn Research Center. The jet flow was observed by quantitative rainbow schlieren deflectometry, a non-intrusive line of sight measurement technique suited for the microgravity environment. The flow structure was characterized by distribution of helium mole fraction obtained from color schlieren images taken at 60 Hz. Results show that the jet in microgravity was up to 70% wider than that in Earth gravity. Experiments reveal that the global flow oscillations observed in Earth are absent in microgravity. Quantitative deatails are provided of the evolution as the experiment undergoes changes in gravity in the drop tower.

  16. Comprehensive Modeling of Superficial Dust Removal via Electrostatic and Dielectrophoretic Forces in Extraterres-trial Exploration Mission

    NASA Technical Reports Server (NTRS)

    Dominguez, Jesus A.; Phillips, James R. III; Mackey, Paul J.; Hogue, Michael D.; Johansen, Michael R.; Cox, Rachel E.; Calle, Carlos I.

    2017-01-01

    The Electrostatics and Surface Physics Laboratory (ESPL) at NASA Kennedy Space Center has developed a dust mitigation technology that uses electrostatic and dielectrophoretic (DEP) forces to disperse and remove the dust already deposited on surfaces preventing the accumulation of dust particles approaching or already deposited on those surfaces.

  17. One-Dimensional Au-ZnO Heteronanostructures for Ultraviolet Light Detectors by a Two-Step Dielectrophoretic Assembly Method.

    PubMed

    Ding, Haitao; Shao, Jinyou; Ding, Yucheng; Liu, Weiyu; Tian, Hongmiao; Li, Xiangming

    2015-06-17

    One-dimensional ZnO decorated with metal nanoparticles has received much attention in the field of ultraviolet light detection because of its high photosensitivity and fast response, while how to form effective metal-ZnO heterostructures cost efficiently is still in development. We report an efficient and well-controlled method to form Au-ZnO heterostructures by two-step dielectrophoretic assembly. First, ZnO nanowires dispersed in deionized water were assembled dielectrophoretically in a planar microelectrode system. To control the number and position of assembled ZnO nanowires, a planar triangle-shaped microelectrode pair was imposed with a high-frequency ac voltage signal in this assembly process. Then a droplet of Au nanoparticle suspension was applied to decorate the preformed ZnO nanowire by another dielectrophoretic assembly process. The near-field dielectrophoretic force induced by the existence of ZnO nanowire spanning the electrode gap attracts Au nanoparticles onto the surface of ZnO nanowires and forms effective Au-ZnO heterostructures. After the adsorption of Au nanoparticles, the performances of Au-ZnO heteronanostructures in UV detection were studied. Experimental results indicate that the ratio of the photo-to-dark current of the Au-ZnO heteronanostucture-based detector was improved significantly, and the photoresponse was accelerated considerably. This kind of enhancement in performance can be attributed to the localized Schottky junctions on the surface of ZnO nanowire which improves the surface band bending.

  18. Using Asymmetric Flow Field-Flow Fractionation (AF4) to Determine C60 Colloidal Size Distributions

    EPA Science Inventory

    The formation of aqueous fullerene suspensions by solvent exchange, sonication, or extended mixing in water is widely reported. Commonly used methods for determining the size of these aggregates rely on static and dynamic light scattering, electron microscopy (EM), or atomic forc...

  19. Using Asymmetric Flow Field-Flow Fractionation (AF4) to Determine C60 Colloidal Size Distributions

    EPA Science Inventory

    The formation of aqueous fullerene suspensions by solvent exchange, sonication, or extended mixing in water is widely reported. Commonly used methods for determining the size of these aggregates rely on static and dynamic light scattering, electron microscopy (EM), or atomic forc...

  20. Field-flow fractionation of nucleic acids and proteins under large-scale gradient magnetic fields

    NASA Astrophysics Data System (ADS)

    Iwasaka, M.

    2007-05-01

    For the purpose of developing techniques for separating biological macromolecules, the present study reports a magnetic chromatography system employing high performance liquid chromatography and superconducting magnets of 14 and 5T. We observed chromatograms of catalase and albumin, which were eluded from columns that were exposed to magnetic fields of up to 14T with a maximum gradient of 90T/m. Without the magnetic fields, the chromatograms of the macromolecules showed a clear peak, while the chromatograms changed to have separated peaks for the same molecules after exposure to gradient magnetic fields. When the chromatocolumn was placed so the magnetic forces were opposite to the direction of flow, the albumin molecules separated into two groups. In addition, the chromatograms of catalase exposed to the magnetic fields indicated that the retention times of the two kinds of magnetically separated catalase were relatively changed if the column-field configuration was changed. Probably, the balance of paramagnetism in the heme and diamagnetism in the protein controlled the transport velocity under the influence of the gradient magnetic fields. In addition, the transport velocity of DNA molecules in the flow with a high gradient magnetic field was observed using a time-resolved spectrophotometric system.

  1. Negative dielectrophoretic force assisted construction of ordered neuronal networks on cell positioning bioelectronic chips.

    PubMed

    Yu, Zhe; Xiang, Guangxin; Pan, Liangbin; Huang, Lihua; Yu, Zhongyao; Xing, Wanli; Cheng, Jing

    2004-12-01

    Developing new methods and technologies in order to pattern neurons into regular networks is of utmost scientific interest in the field of neurological research. An efficient method here is developed for trapping neurons and constructing ordered neuronal networks on bioelectronic chips by using arrayed negative dielectrophoretic (DEP) forces. A special bioelectronic chip with well defined positioning electrode arrays was designed and fabricated on silicon substrate. When a high frequency AC signal was applied, the cell positioning bioelectronic chip (CPBC) is able to provide a well-defined non-uniform electric field, and thus generate negative DEP forces. The parameters, such as size of positioning electrode, conductivity of working solution, amplitude and frequency of power signal and cell concentration, were investigated to optimize the performance of the CPBC. When the neuron suspension was added onto the energized bioelectronic chip, the neurons were immediately trapped and quickly formed the predetermined pattern. Neurons may adhere and then be cultured directly on the CPBC, and show good neuron viability and neurite development. The formation of the ordered neuronal networks after two-week culture demonstrates that negative dielectrophoretic force assisted construction of ordered neuronal networks is effective, and it could be used to assist in monitoring functional activities of neuronal networks.

  2. Dielectrophoretic behavior of PEGylated RNase A inside a microchannel with diamond-shaped insulating posts.

    PubMed

    Mata-Gómez, Marco A; Gallo-Villanueva, Roberto C; González-Valdez, José; Martínez-Chapa, Sergio O; Rito-Palomares, Marco

    2016-02-01

    Ribonuclease A (RNase A) has proven potential as a therapeutic agent, especially in its PEGylated form. Grafting of PEG molecules to this protein yields mono-PEGylated (mono-PEG) and di-PEGylated (di-PEG) RNase A conjugates, and the unreacted protein. Mono-PEG RNase A is of great interest. The use of electrokinetic forces in microdevices represents a novel alternative to chromatographic methods to separate this specie. This work describes the dielectrophoretic behavior of the main protein products of the RNase A PEGylation inside a microchannel with insulators under direct current electric fields. This approach represents the first step in route to design micro-bioprocesses to separate PEGylated RNase A from unreacted native protein. The three proteins exhibited different dielectrophoretic behaviors. All of them experienced a marked streaming pattern at 3000 V consistent with positive dielectrophoresis. Native protein was not captured at any of the conditions tested, while mono-PEG RNase A and di-PEG RNase A were captured presumably due to positive dielectrophoresis at 4000 and 2500 V, respectively. Concentration of mono-PEG RNase A with a maximal enrichment efficiency of ≈9.6 times the feed concentration was achieved in few seconds. These findings open the possibility of designing novel devices for rapid separation, concentration, and recovery of PEGylated RNase A in a one-step operation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Prototype for Automatable, Dielectrophoretically-Accessed Intracellular Membrane–Potential Measurements by Metal Electrodes

    PubMed Central

    Sukhorukov, Vladimir L.; Zimmermann, Dirk

    2013-01-01

    Abstract Functional access to membrane proteins, for example, ion channels, of individual cells is an important prerequisite in drug discovery studies. The highly sophisticated patch-clamp method is widely used for electrogenic membrane proteins, but is demanding for the operator, and its automation remains challenging. The dielectrophoretically-accessed, intracellular membrane–potential measurement (DAIMM) method is a new technique showing high potential for automation of electrophysiological data recording in the whole-cell configuration. A cell suspension is brought between a mm-scaled planar electrode and a μm-scaled tip electrode, placed opposite to each other. Due to the asymmetric electrode configuration, the application of alternating electric fields (1–5 MHz) provokes a dielectrophoretic force acting on the target cell. As a consequence, the cell is accelerated and pierced by the tip electrode, hence functioning as the internal (working) electrode. We used the light-gated cation channel Channelrhodopsin-2 as a reporter protein expressed in HEK293 cells to characterize the DAIMM method in comparison with the patch-clamp technique. PMID:22994967

  4. Dielectrophoretic assembly of dimpled colloids into open packing structures.

    PubMed

    Jia, Zhuoqiang; Sacanna, Stefano; Lee, Stephanie S

    2017-08-30

    Reversible solid-state phase transitions between open- and close-packed structures in two-dimensional colloidal crystals comprising 1.8 μm dimpled spherical colloids were observed using negative dielectrophoresis. These asymmetrically-shaped colloids adopted lattices with cmm plane group symmetry and a packing fraction, ϕ, of 0.68 at low electric field strengths. At high electric field strengths, the close-packed p6m symmetry was observed, with ϕ = 0.90. The transition between open and close-packed structures was found to be reversible, depending on the applied electric field strength and frequency. Finite Fourier transform analysis and COMSOL simulations revealed the existence of repulsive interactions between colloids perpendicular to the electric field lines due to a concentration of the electric field at the edges of the dimpled regions of the colloids. The repulsive interactions resulted in a stretching of the hexagonal lattice perpendicular to the electric field lines, the magnitude of which depended on the electric field strength. By screening the colloids from the electric field in local potential wells, the entropically favored close-packed hexagonal lattice with ϕ = 0.91 was recovered.

  5. Characterization of electrokinetic mobility of microparticles in order to improve dielectrophoretic concentration.

    PubMed

    Martínez-López, José I; Moncada-Hernández, Héctor; Baylon-Cardiel, Javier L; Martínez-Chapa, Sergio O; Rito-Palomares, Marco; Lapizco-Encinas, Blanca H

    2009-05-01

    Insulator-based dielectrophoresis (iDEP), an efficient technique with great potential for miniaturization, has been successfully applied for the manipulation of a wide variety of bioparticles. When iDEP is applied employing direct current (DC) electric fields, other electrokinetic transport mechanisms are present: electrophoresis and electroosmotic flow. In order to concentrate particles, iDEP has to overcome electrokinetics. This study presents the characterization of electrokinetic flow under the operating conditions employed with iDEP; in order to identify the optimal conditions for particle concentration employing DC-iDEP, microparticle image velocimetry (microPIV) was employed to measure the velocity of 1-microm-diameter inert polystyrene particles suspended inside a microchannel made from glass. Experiments were carried out by varying the properties of the suspending medium (conductivity from 25 to 100 microS/cm and pH from 6 to 9) and the strength of the applied electric field (50-300 V/cm); the velocities values obtained ranged from 100 to 700 microm/s. These showed that higher conductivity and lower pH values for the suspending medium produced the lowest electrokinetic flow, improving iDEP concentration of particles, which decreases voltage requirements. These ideal conditions for iDEP trapping (pH = 6 and sigma(m) = 100 microS/cm) were tested experimentally and with the aid of mathematical modeling. The microPIV measurements allowed obtaining values for the electrokinetic mobilities of the particles and the zeta potential of the glass surface; these values were used with a mathematical model built with COMSOL Multiphysics software in order to predict the dielectrophoretic and electrokinetic forces exerted on the particles; the modeling results confirmed the microPIV findings. Experiments with iDEP were carried out employing the same microparticles and a glass microchannel that contained an array of cylindrical insulating structures. By applying DC

  6. Estimation of Metabolism Characteristics for Heat-Injured Bacteria Using Dielectrophoretic Impedance Measurement Method

    NASA Astrophysics Data System (ADS)

    Amako, Eri; Enjoji, Takaharu; Uchida, Satoshi; Tochikubo, Fumiyoshi

    Constant monitoring and immediate control of fermentation processes have been required for advanced quality preservation in food industry. In the present work, simple estimation of metabolic states for heat-injured Escherichia coli (E. coli) in a micro-cell was investigated using dielectrophoretic impedance measurement (DEPIM) method. Temporal change in the conductance between micro-gap (ΔG) was measured for various heat treatment temperatures. In addition, the dependence of enzyme activity, growth capacity and membrane situation for E. coli on heat treatment temperature was also analyzed with conventional biological methods. Consequently, a correlation between ΔG and those biological properties was obtained quantitatively. This result suggests that DEPIM method will be available for an effective monitoring technique for complex change in various biological states of microorganisms.

  7. Modeling of the dielectrophoretic conveyer-belt assembling microparticles into large-scale structures

    NASA Astrophysics Data System (ADS)

    Khusid, Boris; Jacqmin, David; Kumar, Anil; Acrivos, Andreas

    2007-11-01

    A dielectrophoretic conveyor-belt method for assembling negatively polarized microparticles into large-scale structures was recently developed (APL 90, 154104, 2007). To do this, first, an array of microelectrodes is energized to generate a spatially periodic AC electric field that causes the particles to aggregate into boluses in positions of the field intensity- minima, which are located mid-way along the height of the channel. The minima and their associated boluses are then moved by periodically grounding and energizing the electrode array so as to generate an electrical field moving along the electrode array. We simulate this experiment numerically via a two- dimensional electro-hydrodynamic model (PRE 69, 021402, 2004). The numerical results are in qualitative agreement with experiments in that they show similar particle aggregation rates, bolus sizes and bolus transport speeds.

  8. Nanopore sensing at ultra-low concentrations using single-molecule dielectrophoretic trapping

    NASA Astrophysics Data System (ADS)

    Freedman, Kevin J.; Otto, Lauren M.; Ivanov, Aleksandar P.; Barik, Avijit; Oh, Sang-Hyun; Edel, Joshua B.

    2016-01-01

    Single-molecule techniques are being developed with the exciting prospect of revolutionizing the healthcare industry by generating vast amounts of genetic and proteomic data. One exceptionally promising route is in the use of nanopore sensors. However, a well-known complexity is that detection and capture is predominantly diffusion limited. This problem is compounded when taking into account the capture volume of a nanopore, typically 108-1010 times smaller than the sample volume. To rectify this disproportionate ratio, we demonstrate a simple, yet powerful, method based on coupling single-molecule dielectrophoretic trapping to nanopore sensing. We show that DNA can be captured from a controllable, but typically much larger, volume and concentrated at the tip of a metallic nanopore. This enables the detection of single molecules at concentrations as low as 5 fM, which is approximately a 103 reduction in the limit of detection compared with existing methods, while still maintaining efficient throughput.

  9. Dielectrophoretic bending of directly printed free-standing ultra-soft nanowires

    SciTech Connect

    Galliker, P.; Schneider, J.; Poulikakos, D.

    2014-02-17

    Electrohydrodynamic printing has shown superior resolution compared to conventional ink-jet printing, but the use of electrically charged liquid commonly leads to unwanted repulsion effects posing a threshold to resolution capabilities. However, a recently demonstrated controlled dripping process of nanoscale, particle-laden droplets, could circumvent such resolution obstacles even on insulating substrates. Here, we show that so-printed free-standing nanostructures can be autonomously deformed, and mechanically characterized due to the presence of the electrified nozzle, or, after voltage termination, due to transient charge residuals on the structures themselves. Dielectrophoretic forces, arising between two subsequently printed nanopillars lead to their contactless bending and to the formation of out-of-plane arc structures arising from the connection of the pillar apexes. Once connected, the ultra-soft nanopillars are found to be tightly merged and could, for example, serve in electronics as out of plane nanobonds.

  10. Dielectrophoretic bending of directly printed free-standing ultra-soft nanowires

    NASA Astrophysics Data System (ADS)

    Galliker, P.; Schneider, J.; Poulikakos, D.

    2014-02-01

    Electrohydrodynamic printing has shown superior resolution compared to conventional ink-jet printing, but the use of electrically charged liquid commonly leads to unwanted repulsion effects posing a threshold to resolution capabilities. However, a recently demonstrated controlled dripping process of nanoscale, particle-laden droplets, could circumvent such resolution obstacles even on insulating substrates. Here, we show that so-printed free-standing nanostructures can be autonomously deformed, and mechanically characterized due to the presence of the electrified nozzle, or, after voltage termination, due to transient charge residuals on the structures themselves. Dielectrophoretic forces, arising between two subsequently printed nanopillars lead to their contactless bending and to the formation of out-of-plane arc structures arising from the connection of the pillar apexes. Once connected, the ultra-soft nanopillars are found to be tightly merged and could, for example, serve in electronics as out of plane nanobonds.

  11. Impact of surface roughness on Dielectrophoretically assisted concentration of microorganisms over PCB based platforms.

    PubMed

    Bhatt, Geeta; Kant, Rishi; Mishra, Keerti; Yadav, Kuldeep; Singh, Deepak; Gurunath, Ramanathan; Bhattacharya, Shantanu

    2017-06-01

    This article presents a PCB based microfluidic platform for performing a dielectrophoretic capture of live microorganisms over inter-digitated electrodes buried under layers of different surface roughness values. Although dielectrophoresis has been extensively studied earlier over silicon and polymer surfaces with printed electrodes the issue of surface roughness particularly in case of buried electrodes has been seldom investigated. We have addressed this issue through a layer of spin coated PDMS (of various surface roughness) that is used to cover the printed electrodes over a printed circuit board. The roughness in the PDMS layer is generally defined by the roughness of the FR4 base which houses the printed electrodes as well as other structures. Possibilities arising out of COMSOL simulations have been well validated experimentally in this work.

  12. Nanopore sensing at ultra-low concentrations using single-molecule dielectrophoretic trapping.

    PubMed

    Freedman, Kevin J; Otto, Lauren M; Ivanov, Aleksandar P; Barik, Avijit; Oh, Sang-Hyun; Edel, Joshua B

    2016-01-06

    Single-molecule techniques are being developed with the exciting prospect of revolutionizing the healthcare industry by generating vast amounts of genetic and proteomic data. One exceptionally promising route is in the use of nanopore sensors. However, a well-known complexity is that detection and capture is predominantly diffusion limited. This problem is compounded when taking into account the capture volume of a nanopore, typically 10(8)-10(10) times smaller than the sample volume. To rectify this disproportionate ratio, we demonstrate a simple, yet powerful, method based on coupling single-molecule dielectrophoretic trapping to nanopore sensing. We show that DNA can be captured from a controllable, but typically much larger, volume and concentrated at the tip of a metallic nanopore. This enables the detection of single molecules at concentrations as low as 5 fM, which is approximately a 10(3) reduction in the limit of detection compared with existing methods, while still maintaining efficient throughput.

  13. Nanopore sensing at ultra-low concentrations using single-molecule dielectrophoretic trapping

    PubMed Central

    Freedman, Kevin J.; Otto, Lauren M.; Ivanov, Aleksandar P.; Barik, Avijit; Oh, Sang-Hyun; Edel, Joshua B.

    2016-01-01

    Single-molecule techniques are being developed with the exciting prospect of revolutionizing the healthcare industry by generating vast amounts of genetic and proteomic data. One exceptionally promising route is in the use of nanopore sensors. However, a well-known complexity is that detection and capture is predominantly diffusion limited. This problem is compounded when taking into account the capture volume of a nanopore, typically 108–1010 times smaller than the sample volume. To rectify this disproportionate ratio, we demonstrate a simple, yet powerful, method based on coupling single-molecule dielectrophoretic trapping to nanopore sensing. We show that DNA can be captured from a controllable, but typically much larger, volume and concentrated at the tip of a metallic nanopore. This enables the detection of single molecules at concentrations as low as 5 fM, which is approximately a 103 reduction in the limit of detection compared with existing methods, while still maintaining efficient throughput. PMID:26732171

  14. Charged nanoparticle in a nanochannel: Competition between electrostatic and dielectrophoretic forces.

    PubMed

    Hulings, Zachery K; Melnikov, Dmitriy V; Gracheva, Maria E

    2015-06-01

    Nanochannels made in solid-state materials are used for various applications such as nanoparticle separation or DNA manipulation. In this work we examine the effects of the electric and dielectrophoretic forces on a charged nanoparticle confined in a nanochannel. To this end, we solve the Poisson equation for the nanochannel with a wedgelike geometry and consider how channel geometry and electrolyte concentration affect the electrostatic potential distribution and forces acting on nanoparticles of various sizes. On the basis of our calculations, we establish conditions necessary for the particle's attraction to the corners of a channel. We find that for large particles, the net force is attractive only for low concentrations of the electrolyte irrespective of the wedge angle, while small enough particles are attracted to the vertex for either larger electrolyte concentrations or small wedge angle.

  15. Real-time, step-wise, electrical detection of protein molecules using dielectrophoretically aligned SWNT-film FET aptasensors.

    PubMed

    An, Taechang; Kim, Ki Su; Hahn, Sei Kwang; Lim, Geunbae

    2010-08-21

    Aptamer functionalized addressable SWNT-film arrays between cantilever electrodes were successfully developed for biosensor applications. Dielectrophoretically aligned SWNT suspended films made possible highly specific and rapid detection of target proteins with a large binding surface area. Thrombin aptamer immobilized SWNT-film FET biosensor resulted in a real-time, label-free, and electrical detection of thrombin molecules down to a concentration of ca. 7 pM with a step-wise rapid response time of several seconds.

  16. A Simplified Microfluidic Device for Particle Separation with Two Consecutive Steps: Induced Charge Electro-osmotic Prefocusing and Dielectrophoretic Separation.

    PubMed

    Chen, Xiaoming; Ren, Yukun; Liu, Weiyu; Feng, Xiangsong; Jia, Yankai; Tao, Ye; Jiang, Hongyuan

    2017-09-05

    Continuous dielectrophoretic separation is recognized as a powerful technique for a large number of applications including early stage cancer diagnosis, water quality analysis, and stem-cell-based therapy. Generally, the prefocusing of a particle mixture into a stream is an essential process to ensure all particles are subjected to the same electric field geometry in the separation region. However, accomplishing this focusing process either requires hydrodynamic squeezing, which requires an encumbering peripheral system and a complicated operation to drive and control the fluid motion, or depends on dielectrophoretic forces, which are highly sensitive to the dielectric characterization of particles. An alternative focusing technique, induced charge electro-osmosis (ICEO), has been demonstrated to be effective in focusing an incoming mixture into a particle stream as well as nonselective regarding the particles of interest. Encouraged by these aspects, we propose a hybrid method for microparticle separation based on a delicate combination of ICEO focusing and dielectrophoretic deflection. This method involves two steps: focusing the mixture into a thin particle stream via ICEO vortex flow and separating the particles of differing dielectic properties through dielectrophoresis. To demonstrate the feasibility of the method proposed, we designed and fabricated a microfluidic chip and separated a mixture consisting of yeast cells and silica particles with an efficiency exceeding 96%. This method has good potential for flexible integration into other microfluidic chips in the future.

  17. Highly efficient single cell arraying by integrating acoustophoretic cell pre-concentration and dielectrophoretic cell trapping.

    PubMed

    Kim, Soo Hyeon; Antfolk, Maria; Kobayashi, Marina; Kaneda, Shohei; Laurell, Thomas; Fujii, Teruo

    2015-11-21

    To array rare cells at the single-cell level, the volumetric throughput may become a bottleneck in the cell trapping and the subsequent single-cell analysis, since the target cells per definition commonly exist in a large sample volume after purification from the original sample. Here, we present a novel approach for high throughput single cell arraying by integrating two original microfluidic devices: an acoustofluidic chip and an electroactive microwell array. The velocity of the cells is geared down in the acoustofluidic chip while maintaining a high volume flow rate at the inlet of the microsystem, and the cells are subsequently trapped one by one into the microwell array using dielectrophoresis. The integrated system exhibited a 10 times improved sample throughput compared to trapping with the electroactive microwell array chip alone, while maintaining a highly efficient cell recovery above 90%. The results indicate that the serial integration of the acoustophoretic pre-concentration with the dielectrophoretic cell trapping drastically improves the performance of the electroactive microwell array for highly efficient single cell analysis. This simple and effective system for high throughput single cell arraying with further possible integration of additional functions, including cell sorting and downstream analysis after cell trapping, has potential for development to a highly integrated and automated platform for single-cell analysis of rare cells.

  18. Dielectrophoretic isolation and detection of cfc-DNA nanoparticulate biomarkers and virus from blood.

    PubMed

    Sonnenberg, Avery; Marciniak, Jennifer Y; McCanna, James; Krishnan, Rajaram; Rassenti, Laura; Kipps, Thomas J; Heller, Michael J

    2013-04-01

    Dielectrophoretic (DEP) microarray devices allow important cellular nanoparticulate biomarkers and virus to be rapidly isolated, concentrated, and detected directly from clinical and biological samples. A variety of submicron nanoparticulate entities including cell free circulating (cfc) DNA, mitochondria, and virus can be isolated into DEP high-field areas on microelectrodes, while blood cells and other micron-size entities become isolated into DEP low-field areas between the microelectrodes. The nanoparticulate entities are held in the DEP high-field areas while cells are washed away along with proteins and other small molecules that are not affected by the DEP electric fields. DEP carried out on 20 μL of whole blood obtained from chronic lymphocytic leukemia patients showed a considerable amount of SYBR Green stained DNA fluorescent material concentrated in the DEP high-field regions. Whole blood obtained from healthy individuals showed little or no fluorescent DNA materials in the DEP high-field regions. Fluorescent T7 bacteriophage virus could be isolated directly from blood samples, and fluorescently stained mitochondria could be isolated from biological buffer samples. Using newer DEP microarray devices, high-molecular-weight DNA could be isolated from serum and detected at levels as low as 8-16 ng/mL. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Rapid formation of cell-particle complexes via dielectrophoretic manipulation for the detection of surface antigens.

    PubMed

    Horii, Takuma; Yamamoto, Masashi; Yasukawa, Tomoyuki; Mizutani, Fumio

    2014-11-15

    A rapid and simple method for the fabrication of the island patterns with particles and cells was applied to detect the presence of specific antigens on the cell surface. An upper interdigitated microband array (IDA) electrode was mounted on a lower substrate with the same design to fabricate a microfluidic-channel device for dielectrophoretic manipulation. The electrode grid structure was fabricated by rotating the upper template IDA by 90° relative to the lower IDA. A suspension of anti-CD33 modified particles and HL-60 cells was introduced into the channel. An AC electrical signal (typically 20 V peak-to-peak, 100 kHz) was then applied to the bands of the upper and lower IDAs, resulting in the formation of island patterns at the intersections with low electric fields. Immunoreactions between the antibodies immobilized on the accumulated particles and the CD33 present on the surface of the cells led to the formation of complexes comprising corresponding antigen-antibody pairs. Non-specific pairs accumulated at the intersection, which did not form complexes, were then dispersed after removal of the applied field. The time required for the detection of the formation/dispersion of the complexes is as short as 6 min in the present procedure. Furthermore, this novel cell binding assay does not require pretreatment such as target labeling or washing of the unbound cells.

  20. Continuous-mode dielectrophoretic gating for highly efficient separation of analytes in surface micromachined microfluidic devices

    NASA Astrophysics Data System (ADS)

    Song, Hongjun; Mulukutla, Vishwanath; James, Conrad D.; Bennett, Dawn J.

    2008-12-01

    Here, we describe a dielectrophoretic (DEP) gating technique for preconcentrating and separating biological and non-biological particles in a microfluidic device. The microfluidic devices are surface-micromachined on silicon substrates and are fully encapsulated without substrate bonding procedures. DEP gates in the devices consist of embedded microelectrodes that are coupled to the fluid channels for analyte manipulation with electric fields. We consider several different microelectrode designs such as low and high radius-of-curvature edges, and we detail the time- and frequency-dependent preconcentration of particles. Simulations of the particle motion under the manipulation of DEP forces are found to be in good agreement with the experimental results. Experimental results show that bioparticles such as Penicillium brevicompactum (PBC), T-cells and Escherichia coli (E. coli) undergo positive DEP and are trapped in regions of large electric-field gradient adjacent to the DEP gate. In contrast to our previous demonstration of batch-mode separation of particles with different dielectric properties, here we perform a continuous-mode separation of latex particles and E. coli from a mixture.

  1. Dynamic evolution of interacting carbon nanotubes suspended in a fluid using a dielectrophoretic framework

    NASA Astrophysics Data System (ADS)

    Oliva-Avilés, A. I.; Zozulya, V. V.; Gamboa, F.; Avilés, F.

    2016-09-01

    A theoretical investigation of the dynamic response of interacting carbon nanotubes (CNTs) dispersed in a liquid medium under alternating current electric fields is presented. The proposed modeling strategy is based on the dielectrophoretic theory and classical electrodynamics of rigid bodies, and considers the coupled rotation-translation motion of interacting CNTs represented as electrical dipoles. Based on experimental evidence, the parameters which are expected to cause a major contribution to the CNTs' motion are investigated for different initial configurations of CNTs. It is predicted that high electric field frequencies, long CNTs, high values of electrical permittivity and conductivity of the CNTs immersed in solvents of high polarity promote faster equilibrium conditions, achieved by CNT tip-to-tip contact and alignment along the electric field direction. For the majority of the scenarios, CNT alignment along the field direction is predicted as the first event, followed by the translation of aligned CNTs until the tip-to-tip contact condition is reached. For systems with interacting CNTs with different lengths, equilibrium of the shorter CNT is achieved faster. Predictions also show that the initial rotation angles and initial location of CNTs have a paramount influence on the evolution of the system towards the equilibrium configuration.

  2. Electronic detection of dielectrophoretic forces exerted on particles flowing over interdigitated electrodes.

    PubMed

    Nikolic-Jaric, Marija; Romanuik, Sean F; Ferrier, Graham A; Cabel, Tim; Salimi, Elham; Levin, David B; Bridges, Greg E; Thomson, Douglas J

    2012-06-01

    Dielectric particles flowing through a microfluidic channel over a set of coplanar electrodes can be simultaneously capacitively detected and dielectrophoretically (DEP) actuated when the high (1.45 GHz) and low (100 kHz-20 MHz) frequency electromagnetic fields are concurrently applied through the same set of electrodes. Assuming a simple model in which the only forces acting upon the particles are apparent gravity, hydrodynamic lift, DEP force, and fluid drag, actuated particle trajectories can be obtained as numerical solutions of the equations of motion. Numerically calculated changes of particle elevations resulting from the actuation simulated in this way agree with the corresponding elevation changes estimated from the electronic signatures generated by the experimentally actuated particles. This verifies the model and confirms the correlation between the DEP force and the electronic signature profile. It follows that the electronic signatures can be used to quantify the actuation that the dielectric particle experiences as it traverses the electrode region. Using this principle, particles with different dielectric properties can be effectively identified based exclusively on their signature profile. This approach was used to differentiate viable from non-viable yeast cells (Saccharomyces cerevisiae).

  3. A review of microfabrication techniques and dielectrophoretic microdevices for particle manipulation and separation

    NASA Astrophysics Data System (ADS)

    Li, M.; Li, W. H.; Zhang, J.; Alici, G.; Wen, W.

    2014-02-01

    The development of lab-on-a-chip (LOC) devices over the past decade has attracted growing interest. LOC devices aim to achieve the miniaturization, integration, automation and parallelization of biological and chemical assays. One of the applications, the ability to effectively and accurately manipulate and separate micro- and nano-scale particles in an aqueous solution, is particularly appealing in biological, chemical and medical fields. Among the technologies that have been developed and implemented in microfluidic microsystems for particle manipulation and separation (such as mechanical, inertial, hydrodynamic, acoustic, optical, magnetic and electrical methodologies), dielectrophoresis (DEP) may prove to be the most popular because of its label-free nature, ability to manipulate neutral bioparticles, analyse with high selectivity and sensitivity, compatibility with LOC devices, and easy and direct interface with electronics. The required spatial electric non-uniformities for the DEP effect can be generated by patterning microelectrode arrays within microchannels, or placing insulating obstacles within a microchannel and curving the microchannels. A wide variety of electrode- and insulator-based DEP microdevices have been developed, fabricated, and successfully employed to manipulate and separate bioparticles (i.e. DNA, proteins, bacteria, viruses, mammalian and yeast cells). This review provides an overview of the state-of-the-art of microfabrication techniques and of the structures of dielectrophoretic microdevices aimed towards different applications. The techniques used for particle manipulation and separation based on microfluidics are provided in this paper. In addition, we also present the theoretical background of DEP.

  4. An Inverted Dielectrophoretic Device for Analysis of Attached Single Cell Mechanics

    PubMed Central

    Urbano, Rebecca Lownes; Clyne, Alisa Morss

    2016-01-01

    Dielectrophoresis (DEP), the force induced on a polarizable body by a non-uniform electric field, has been widely used to manipulate single cells in suspension and analyze their stiffness. However, most cell types do not naturally exist in suspension but instead require attachment to the tissue extracellular matrix in vivo. Cells alter their cytoskeletal structure when they attach to a substrate, which impacts cell stiffness. It is therefore critical to be able to measure mechanical properties of cells attached to a substrate. We present a novel inverted quadrupole dielectrophoretic device capable of measuring changes in the mechanics of single cells attached to a micropatterned polyacrylamide gel. The device is positioned over a cell of defined size, a directed DEP pushing force is applied, and cell centroid displacement is dynamically measured by optical microscopy. Using this device, single endothelial cells showed greater centroid displacement in response to applied DEP pushing force following actin cytoskeleton disruption by cytochalasin D. In addition, transformed mammary epithelial cell (MCF10A-NeuT) showed greater centroid displacement in response to applied DEP pushing force compared to untransformed cells (MCF10A). DEP device measurements were confirmed by showing that the cells with greater centroid displacement also had a lower elastic modulus by atomic force microscopy. The current study demonstrates that an inverted DEP device can determine changes in single attached cell mechanics on varied substrates. PMID:26738543

  5. Microfluidic multifunctional probe array dielectrophoretic force spectroscopy with wide loading rates.

    PubMed

    Park, In Soo; Eom, Kilho; Son, Jongsang; Chang, Woo-Jin; Park, Kidong; Kwon, Taeyun; Yoon, Dae Sung; Bashir, Rashid; Lee, Sang Woo

    2012-10-23

    The simultaneous investigation of a large number of events with different types of intermolecular interactions, from nonequilibrium high-force pulling assays to quasi-equilibrium unbinding events in the same environment, can be very important for fully understanding intermolecular bond-rupture mechanisms. Here, we describe a novel dielectrophoretic force spectroscopy technique that utilizes microsized beads as multifunctional probes for parallel measurement of intermolecular forces with an extremely wide range of force rate (10(-4) to 10(4) pN/s) inside a microfluidic device. In our experiments, various forces, which broadly form the basis of all molecular interactions, were measured across a range of force loading rates by multifunctional probes of various diameters with a throughput of over 600 events per mm(2), simultaneously and in the same environment. Furthermore, the individual bond-rupture forces, the parameters for the characterization of entire energy landscapes, and the effective stiffness of the force spectroscopy were determined on the basis of the measured results. This method of determining intermolecular forces could be very useful for the precise and simultaneous examination of various molecular interactions, as it can be easily and cost-effectively implemented within a microfluidic device for a range of applications including immunoassays, molecular mechanics, chemical and biological screening, and mechanobiology.

  6. Dielectrophoretic capture voltage spectrum for measurement of dielectric properties and separation of cancer cells

    PubMed Central

    Wu, Liqun; Lanry Yung, Lin-Yue; Lim, Kian-Meng

    2012-01-01

    In this paper, a new dielectrophoresis (DEP) method based on capture voltage spectrum is proposed for measuring dielectric properties of biological cells. The capture voltage spectrum can be obtained from the balance of dielectrophoretic force and Stokes drag force acting on the cell in a microfluidic device with fluid flow and strip electrodes. The method was demonstrated with the measurement of dielectric properties of human colon cancer cells (HT-29 cells). From the capture voltage spectrum, the real part of Clausius–Mossotti factor of HT-29 cells for different frequencies of applied electric field was obtained. The dielectric properties of cell interior and plasma membrane were then estimated by using single-shell dielectric model. The cell interior permittivity and conductivity were found to be insensitive to changes in the conductivity of the medium in which the cells are suspended, but the measured permittivity and conductivity of cell membrane were found to increase with the increase of medium conductivity. In addition, the measurement of capture voltage spectrum was found to be useful in providing the optimum operating conditions for separating HT-29 cells from other cells (such as red blood cells) using dielectrophoresis. PMID:22662097

  7. Combined dielectrophoretic and impedance system for on-chip controlled bacteria concentration: Application to Escherichia coli.

    PubMed

    Del Moral-Zamora, Beatriz; Punter-Villagrassa, Jaime; Oliva-Brañas, Ana M; Álvarez-Azpeitia, Juan Manuel; Colomer-Farrarons, Jordi; Samitier, Josep; Homs-Corbera, Antoni; Miribel-Català, Pere Ll

    2015-05-01

    The present paper reports a bacteria autonomous controlled concentrator prototype with a user-friendly interface for bench-top applications. It is based on a microfluidic lab-on-a-chip and its associated custom instrumentation, which consists of a dielectrophoretic actuator, to preconcentrate the sample, and an impedance analyzer, to measure concentrated bacteria levels. The system is composed of a single microfluidic chamber with interdigitated electrodes and an instrumentation with custom electronics. The prototype is supported by a real-time platform connected to a remote computer, which automatically controls the system and displays impedance data used to monitor the status of bacteria accumulation on-chip. The system automates the whole concentrating operation. Performance has been studied for controlled volumes of Escherichia coli samples injected into the microfluidic chip at constant flow rate of 10 μL/min. A media conductivity correcting protocol has been developed, as the preliminary results showed distortion of the impedance analyzer measurement produced by bacterial media conductivity variations through time. With the correcting protocol, the measured impedance values were related to the quantity of bacteria concentrated with a correlation of 0.988 and a coefficient of variation of 3.1%. Feasibility of E. coli on-chip automated concentration, using the miniaturized system, has been demonstrated. Furthermore, the impedance monitoring protocol had been adjusted and optimized, to handle changes in the electrical properties of the bacteria media over time.

  8. Predicting the disorder-order transition of dielectrophoretic colloidal assembly with dielectric spectroscopy.

    PubMed

    Beltramo, Peter J; Furst, Eric M

    2013-04-01

    The dielectrophoretic assembly of colloidal suspensions into crystalline arrays is described by a master scaling that collapses the disorder-order transition as a function of field strength, frequency, and particle size. This master scaling has been verified for particle diameters ranging from 2a = 200 nm to 3 μm by light scattering (Lumsdon et al., Langmuir 2004, 20, 2108-2116; McMullan and Wagner, Langmuir 2012, 28, 4123-4130), optical laser tweezer measurements (Mittal et al., J. Chem. Phys. 2008, 129, 064513), and small-angle neutron scattering (McMullan and Wagner, Soft Matter 2010, 6, 5443-5450). In this work, we reconcile the empirical phase diagram with direct measurements of the colloid polarizability using dielectric spectroscopy. Dielectric spectroscopy confirms the origin of the order-disorder transition frequency dependence, including its quadratic scaling with particle radius, a(2), and provides an alternative method to search for optimal self-assembly conditions. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Computational Fluid Dynamics Modelling of Microfluidic Channel for Dielectrophoretic BioMEMS Application

    PubMed Central

    Low, Wan Shi; Kadri, Nahrizul Adib; Wan Abas, Wan Abu Bakar bin

    2014-01-01

    We propose a strategy for optimizing distribution of flow in a typical benchtop microfluidic chamber for dielectrophoretic application. It is aimed at encouraging uniform flow velocity along the whole analysis chamber in order to ensure DEP force is evenly applied to biological particle. Via the study, we have come up with a constructive strategy in improving the design of microfluidic channel which will greatly facilitate the use of DEP system in laboratory and primarily focus on the relationship between architecture and cell distribution, by resorting to the tubular structure of blood vessels. The design was validated by hydrodynamic flow simulation using COMSOL Multiphysics v4.2a software. Simulations show that the presence of 2-level bifurcation has developed portioning of volumetric flow which produced uniform flow across the channel. However, further bifurcation will reduce the volumetric flow rate, thus causing undesirable deposition of cell suspension around the chamber. Finally, an improvement of microfluidic design with rounded corner is proposed to encourage a uniform cell adhesion within the channel. PMID:25136701

  10. An inverted dielectrophoretic device for analysis of attached single cell mechanics.

    PubMed

    Lownes Urbano, Rebecca; Morss Clyne, Alisa

    2016-02-07

    Dielectrophoresis (DEP), the force induced on a polarizable body by a non-uniform electric field, has been widely used to manipulate single cells in suspension and analyze their stiffness. However, most cell types do not naturally exist in suspension but instead require attachment to the tissue extracellular matrix in vivo. Cells alter their cytoskeletal structure when they attach to a substrate, which impacts cell stiffness. It is therefore critical to be able to measure mechanical properties of cells attached to a substrate. We present a novel inverted quadrupole dielectrophoretic device capable of measuring changes in the mechanics of single cells attached to a micropatterned polyacrylamide gel. The device is positioned over a cell of defined size, a directed DEP pushing force is applied, and cell centroid displacement is dynamically measured by optical microscopy. Using this device, single endothelial cells showed greater centroid displacement in response to applied DEP pushing force following actin cytoskeleton disruption by cytochalasin D. In addition, transformed mammary epithelial cell (MCF10A-NeuT) showed greater centroid displacement in response to applied DEP pushing force compared to untransformed cells (MCF10A). DEP device measurements were confirmed by showing that the cells with greater centroid displacement also had a lower elastic modulus by atomic force microscopy. The current study demonstrates that an inverted DEP device can determine changes in single attached cell mechanics on varied substrates.

  11. Computational fluid dynamics modelling of microfluidic channel for dielectrophoretic BioMEMS application.

    PubMed

    Low, Wan Shi; Kadri, Nahrizul Adib; Abas, Wan Abu Bakar bin Wan

    2014-01-01

    We propose a strategy for optimizing distribution of flow in a typical benchtop microfluidic chamber for dielectrophoretic application. It is aimed at encouraging uniform flow velocity along the whole analysis chamber in order to ensure DEP force is evenly applied to biological particle. Via the study, we have come up with a constructive strategy in improving the design of microfluidic channel which will greatly facilitate the use of DEP system in laboratory and primarily focus on the relationship between architecture and cell distribution, by resorting to the tubular structure of blood vessels. The design was validated by hydrodynamic flow simulation using COMSOL Multiphysics v4.2a software. Simulations show that the presence of 2-level bifurcation has developed portioning of volumetric flow which produced uniform flow across the channel. However, further bifurcation will reduce the volumetric flow rate, thus causing undesirable deposition of cell suspension around the chamber. Finally, an improvement of microfluidic design with rounded corner is proposed to encourage a uniform cell adhesion within the channel.

  12. Modeling and characterization of dielectrophoretically structured piezoelectric composites using piezoceramic particle inclusions with high aspect ratios

    NASA Astrophysics Data System (ADS)

    van den Ende, D. A.; Maier, R. A.; van Neer, P. L. M. J.; van der Zwaag, S.; Randall, C. A.; Groen, W. A.

    2013-01-01

    In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT—polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the composites are compared to those of PZT-polymer composites with equiaxed particles, continuous PZT fiber-polymer composites, and bulk PZT ceramics. From high-field polarization and strain measurements, the effective field dependent permittivity and piezoelectric charge constant in the poling direction are determined for dielectrophoresis structured PZT-polymer composites, continuous PZT fiber-polymer composites, and bulk PZT ceramics. The changes in dielectric properties of the inclusions and the matrix at high fields influence the dielectric and piezoelectric properties of the composites. It is found that the permittivity and piezoelectric charge constants increase towards a maximum at an applied field of around 2.5-5 kV/mm. The electric field at which the maximum occurs depends on the aspect ratio and degree of alignment of the inclusions. Experimental values of d33 at low and high applied fields are compared to a model describing the composites as a continuous polymer matrix containing PZT particles of various aspect ratios arranged into chains. Thickness mode coupling factors were determined from measured impedance data using fitted equivalent circuit model simulations. The relatively high piezoelectric strain constants, voltage constants, and thickness coupling factors indicate that such aligned short fiber composites could be useful as flexible large area transducers.

  13. Enhanced cell viability and cell adhesion using low conductivity medium for negative dielectrophoretic cell patterning.

    PubMed

    Puttaswamy, Srinivasu Valagerahally; Sivashankar, Shilpa; Chen, Rong-Jhe; Chin, Chung-Kuang; Chang, Hwan-You; Liu, Cheng Hsien

    2010-10-01

    Negative dielectrophoretic (n-DEP) cell manipulation is an efficient way to pattern human liver cells on micro-electrode arrays. Maintaining cell viability is an important objective for this approach. This study investigates the effect of low conductivity medium and the optimally designed microchip on cell viability and cell adhesion. To explore the influence of conductivity on cell viability and cell adhesion, we have used earlier reported dielectrophoresis (DEP) buffer with a conductivity of 10.2 mS/m and three formulated media with conductivity of 9.02 (M1), 8.14 (M2), 9.55 (M3) mS/m. The earlier reported isotonic sucrose/dextrose buffer (DEP buffer) used for DEP manipulation has the drawback of poor cell adhesion and cell viability. A microchip prototype with well-defined positioning of titanium electrode arrays was designed and fabricated on a glass substrate. The gap between the radial electrodes was accurately determined to achieve good cell patterning performance. Parameters such as dimension of positioning electrode, amplitude, and frequency of voltage signal were investigated to optimize the performance of the microchip.

  14. Bacterial handling under the influence of non-uniform electric fields: dielectrophoretic and electrohydrodynamic effects.

    PubMed

    Fernádez-Morales, Flavio H; Duarte, Julio E; Samitier-Martí, Josep

    2008-12-01

    This paper describes the modeling and experimental verification of a castellated microelectrode array intended to handle biocells, based on common dielectrophoresis. The proposed microsystem was developed employing platinum electrodes deposited by lift-off, silicon micromachining, and photoresin patterning techniques. Having fabricated the microdevice it was tested employing Escherichia coli as bioparticle model. Positive dielectrophoresis could be verified with the selected cells for frequencies above 100 kHz, and electrohydrodynamic effects were observed as the dominant phenomena when working at lower frequencies. As a result, negative dielectrophoresis could not be observed because its occurrence overlaps with electrohydrodynamic effects; i.e. the viscous drag force acting on the particles is greater than the dielectrophoretic force at frequencies where negative dielectrophoresis should occur. The experiments illustrate the convenience of this kind of microdevices to micro handling biological objects, opening the possibility for using these microarrays with other bioparticles. Additionally, liquid motion as a result of electrohydrodynamic effects must be taken into account when designing bioparticle micromanipulators, and could be used as mechanism to clean the electrode surfaces, that is one of the most important problems related to this kind of devices.

  15. Correlation between dielectric property by dielectrophoretic levitation and growth activity of cells exposed to electric field.

    PubMed

    Hakoda, Masaru; Hirota, Yusuke

    2013-09-01

    The purpose of this study is to develop a system analyzing cell activity by the dielectrophoresis method. Our previous studies revealed a correlation between the growth activity and dielectric property (Re[K(ω)]) of mouse hybridoma 3-2H3 cells using dielectrophoretic levitation. Furthermore, it was clarified that the differentiation activity of many stem cells could be evaluated by the Re[K(ω)] without differentiation induction. In this paper, 3-2H3 cells exposed to an alternating current (AC) electric field or a direct current (DC) electric field were cultivated, and the influence of damage by the electric field on the growth activity of the cells was examined. To evaluate the activity of the cells by measuring the Re[K(ω)], the correlation between the growth activity and the Re[K(ω)] of the cells exposed to the electric field was examined. The relations between the cell viability, growth activity, and Re[K(ω)] in the cells exposed to the AC electric field were obtained. The growth activity of the cells exposed to the AC electric field could be evaluated by the Re[K(ω)]. Furthermore, it was found that the adverse effects of the electric field on the cell viability and the growth activity were smaller in the AC electric field than the DC electric field.

  16. Dielectrophoretic sample preparation for environmental monitoring of microorganisms: Soil particle removal.

    PubMed

    Fatoyinbo, Henry O; McDonnell, Martin C; Hughes, Michael P

    2014-07-01

    Detection of pathogens from environmental samples is often hampered by sensors interacting with environmental particles such as soot, pollen, or environmental dust such as soil or clay. These particles may be of similar size to the target bacterium, preventing removal by filtration, but may non-specifically bind to sensor surfaces, fouling them and causing artefactual results. In this paper, we report the selective manipulation of soil particles using an AC electrokinetic microfluidic system. Four heterogeneous soil samples (smectic clay, kaolinitic clay, peaty loam, and sandy loam) were characterised using dielectrophoresis to identify the electrical difference to a target organism. A flow-cell device was then constructed to evaluate dielectrophoretic separation of bacteria and clay in a continous flow through mode. The average separation efficiency of the system across all soil types was found to be 68.7% with a maximal separation efficiency for kaolinitic clay at 87.6%. This represents the first attempt to separate soil particles from bacteria using dielectrophoresis and indicate that the technique shows significant promise; with appropriate system optimisation, we believe that this preliminary study represents an opportunity to develop a simple yet highly effective sample processing system.

  17. Modifying dielectrophoretic response of nonviable yeast cells by ionic surfactant treatment.

    PubMed

    Tang, Shi-Yang; Zhang, Wei; Baratchi, Sara; Nasabi, Mahyar; Kalantar-Zadeh, Kourosh; Khoshmanesh, Khashayar

    2013-07-02

    Nonviable cells are essential biosystems, due to the functionalities they offer and their effects on viable cells. Therefore, the separation and immobilization of nonviable cells separately or in the vicinity of viable cells is of great importance for many fundamentals investigations in cell biology. However, most nonviable cells become less polarizable than the surrounding medium at conductivities above 0.01 S/m. This means that in such a medium, dielectrophoresis, despite its great versatilities for manipulation of cells, cannot be employed for immobilizing nonviable cells. Here, we present a novel approach to change the dielectrophoretic (DEP) response of nonviable yeast cells by treating them with low concentrations of ionic surfactants such as sodium dodecyl sulfate. After this treatment, they exhibit a strong positive DEP response, even at high medium conductivities. The capability of this treatment is demonstrated in two proof-of-concept experiments. First, we show the sorting and immobilization of viable and nonviable yeast cells, along consecutive microelectrode arrays. Second, we demonstrate the immobilization of viable and nonviable cells in the vicinity of each other along the same microelectrode array. The proposed technique allows DEP platforms to be utilized for the immobilization and subsequent postanalysis of both viable and nonviable cells with and without the presence of each other.

  18. Performance impact of dynamic surface coatings on polymeric insulator-based dielectrophoretic particle separators.

    PubMed

    Davalos, Rafael V; McGraw, Gregory J; Wallow, Thomas I; Morales, Alfredo M; Krafcik, Karen L; Fintschenko, Yolanda; Cummings, Eric B; Simmons, Blake A

    2008-02-01

    Efficient and robust particle separation and enrichment techniques are critical for a diverse range of lab-on-a-chip analytical devices including pathogen detection, sample preparation, high-throughput particle sorting, and biomedical diagnostics. Previously, using insulator-based dielectrophoresis (iDEP) in microfluidic glass devices, we demonstrated simultaneous particle separation and concentration of various biological organisms, polymer microbeads, and viruses. As an alternative to glass, we evaluate the performance of similar iDEP structures produced in polymer-based microfluidic devices. There are numerous processing and operational advantages that motivate our transition to polymers such as the availability of numerous innate chemical compositions for tailoring performance, mechanical robustness, economy of scale, and ease of thermoforming and mass manufacturing. The polymer chips we have evaluated are fabricated through an injection molding process of the commercially available cyclic olefin copolymer Zeonor 1060R. This publication is the first to demonstrate insulator-based dielectrophoretic biological particle differentiation in a polymeric device injection molded from a silicon master. The results demonstrate that the polymer devices achieve the same performance metrics as glass devices. We also demonstrate an effective means of enhancing performance of these microsystems in terms of system power demand through the use of a dynamic surface coating. We demonstrate that the commercially available nonionic block copolymer surfactant, Pluronic F127, has a strong interaction with the cyclic olefin copolymer at very low concentrations, positively impacting performance by decreasing the electric field necessary to achieve particle trapping by an order of magnitude. The presence of this dynamic surface coating, therefore, lowers the power required to operate such devices and minimizes Joule heating. The results of this study demonstrate that iDEP polymeric

  19. Creation of carbon nanotube based bioSensors through dielectrophoretic assembly

    NASA Astrophysics Data System (ADS)

    Mani, Nilan S.; Kim, Steve; Annam, Kaushik; Bane, Danielle; Subramanyam, Guru

    2015-08-01

    Due to their excellent electrical, optical, and mechanical properties, nanosized single wall carbon nanotubes (SWNTs) have attracted significant attention as a transducing element in nano-bio sensor research. Controlled assembly, device fabrication, and bio-functionalization of the SWNTs are crucial in creating the sensors. In this study, working biosensor platforms were created using dielectrophoretic assembly of single wall carbon nanotubes (SWNTs) as a bridge between two gold electrodes. SWNTs in a commercial SDS surfactant solution were dispensed in the gap between the two gold electrodes, followed by applying an ac voltage across the two electrodes. The dielectrophoresis aligns the CNTs and forms a bridge between the two electrodes. A copious washing and a subsequent annealing of the devices at 200 °C remove the surfactants and create an excellent semiconducting (p-type) bridge between the two electrodes. A liquid gated field effect transistor (LGFET) was built using DI water as the gate dielectric and the SWNT bridge as the channel. Negative gate voltages of the FET increased the drain current and applying a positive gate voltage of +0.5V depleted the channel of charges and turned the device off. The biosensor was verified using both the two terminal and three terminal devices. Genomic salmon DNA dissolved in DI water was applied on the SWNT bridge in both type of devices. In the two terminal device, the conductance of the bridge dropped by 65x after the binding of the DNA. In the LGFET, the transconductance of the device decreased 2X after the binding of the DNA. The binding of the DNA also suppressed hysteresis in the Drain Current vs Gate Voltage characteristics of the LGFET.

  20. Lab on a chip for multiplexed immunoassays to detect bladder cancer using multifunctional dielectrophoretic manipulations.

    PubMed

    Chuang, Cheng-Hsin; Wu, Ting-Feng; Chen, Cheng-Ho; Chang, Kai-Chieh; Ju, Jing-Wei; Huang, Yao-Wei; Van Nhan, Vo

    2015-07-21

    A multiplexed immunosensor has been developed for the detection of specific biomarkers Galectin-1 (Gal-1) and Lactate Dehydrogenase B (LDH-B) present in different grades of bladder cancer cell lysates. In order to immobilize nanoprobes with different antibodies on a single chip we employed three-step programmable dielectrophoretic manipulations for focusing, guiding and trapping to enhance the fluorescent response and reduce the interference between the two antibody arrays. The chip consisted of a patterned indium tin oxide (ITO) electrode for sensing and a middle fish bone shaped gold electrode for focusing and guiding. Using ITO electrodes for the sensing area can effectively eliminate the background noise of fluorescence response as compared to metal electrodes. It was also observed that the three step manipulation increased fluorescence response after immunosensing by about 4.6 times as compared to utilizing DEP for just trapping the nanoprobes. Two different-grade bladder cancer cell lysates (grade I: RT4 and grade III: T24) were individually analyzed for detecting the protein expression levels of Gal-1 and LDH-B. The fluorescence intensity observed for Gal-1 is higher than that of LDH-B in the T24 cell lysate; however the response observed in RT4 is higher for LDH-B as compared to Gal-1. Thus we can effectively identify the different grades of bladder cancer cells. In addition, the platform for DEP manipulation developed in this study can enable real time detection of multiple analytes on a single chip and provide more practical benefits for clinical diagnosis.

  1. Capillary-driven microfluidic chips with evaporation-induced flow control and dielectrophoretic microbead trapping

    NASA Astrophysics Data System (ADS)

    Temiz, Yuksel; Skorucak, Jelena; Delamarche, Emmanuel

    2014-03-01

    This work reports our efforts on developing simple-to-use microfluidic devices for point-of-care diagnostic applications with recent extensions that include the trapping of microbeads using dielectrophoresis (DEP) and the modulation of capillary-driven flow using integrated microheaters. DEP serves the purpose of trapping microbeads coated with receptors and analytes for detection of a fluorescent signal. The microheater is actuated once the chip is filled by capillarity, creating an evaporation-induced flow tuned according to assay conditions. The chips are composed of a glass substrate patterned with 50-nm-thick Pd electrodes and microfluidic structures made using a 20-μm-thick dry-film resist (DFR). Chips are covered/sealed by low-temperature (50 °C) lamination of a 50-μm-thick DFR layer having excellent optical and mechanical properties. To separate cleaned and sealed chips from the wafer, we used an effective chip singulation technique that we informally call the "chip-olate" process. In the experimental section, we first studied dielectrophoretic trapping of 10 μm beads for flow rates ranging from 80 pL s-1 to 2.5 nL s-1 and that are generated by an external syringe pump. Then, we characterized the embedded microheater in DFR-covered chips. Flow rates as high as 8 nL s-1 were generated by evaporation-induced flow when the heater was biased by 10 V, corresponding to 270 mW power. Finally, DEP-based trapping and fluorescent detection of functionalized beads were demonstrated as the flow was generated by the combination of capillary filling and evaporation-induced flow.

  2. Capillary-driven microfluidic chips with evaporation-induced flow control and dielectrophoretic microbead trapping

    NASA Astrophysics Data System (ADS)

    Temiz, Yuksel; Skorucak, Jelena; Delamarche, Emmanuel

    2014-07-01

    This work reports our efforts on developing simple-to-use microfluidic devices for point-of-care diagnostic applications with recent extensions that include the trapping of microbeads using dielectrophoresis (DEP) and the modulation of the liquid flow using integrated microheaters. DEP serves the purpose of trapping microbeads coated with receptors and analytes for detection of a fluorescent signal. The microheater is actuated once the chip is filled by capillarity, creating an evaporation-induced flow tuned according to assay conditions. The chips are composed of a glass substrate patterned with 50-nm-thick Pd electrodes and microfluidic structures made using a 20-μm-thick dry-film resist (DFR). Chips are covered/sealed by low temperature (50°C) lamination of a 50-μm-thick DFR layer having excellent optical and mechanical properties. To separate cleaned and sealed chips from the wafer, we used an effective chip singulation technique which we informally call the "chip-olate" process. In the experimental section, we first studied dielectrophoretic trapping of 10-μm beads for flow rates ranging from 80 pL s-1 to 2.5 nL s-1 that are generated by an external syringe pump. Then, we characterized the embedded microheater in DFR-covered chips. Flow rates as high as 8 nL s-1 were generated by evaporation-induced flow when the heater was biased by 10 V, corresponding to 270-mW power. Finally, DEP-based trapping and fluorescent detection of functionalized beads were demonstrated as the flow was generated by evaporation-induced flow after the microfluidic structures were filled by capillarity.

  3. Design of insulator-based dielectrophoretic devices: Effect of insulator posts characteristics.

    PubMed

    Saucedo-Espinosa, M A; Lapizco-Encinas, B H

    2015-11-27

    Insulator-based dielectrophoresis (iDEP) is a leading technique for the enrichment and manipulation of target bioparticles by exploiting physical and electrical properties of the particles and the suspending medium. Dielectrophoretic forces are produced by employing insulator posts that distort an otherwise uniform electric field. The optimal design for iDEP devices involves a careful balance between electrokinetics (EK) and dielectrophoresis (DEP) in the DEP-active area, where the design of the insulator posts is crucial for their performance. This contribution demonstrates the selection of a geometrical set of parameters that enhances particle capture and enrichment in an iDEP device. Numerical simulations, comprising an average trapping condition (TC) and the average lateral-to-longitudinal force ratio (FR) experienced by particles, were used to determine improved geometrical parameters (e.g., shape, length and width) and arrangement (e.g., lateral and longitudinal spacing) of the insulator posts. Experiments with polystyrene particles demonstrated the enhancement in particle enrichment, validating the employed key output parameters. The fabrication feasibility of the improved devices by a soft-lithographic process was also explored through numerical simulations and experiments. Optimal designs for this study were selected and their capture capacity was examined, demonstrating a decrease up to 84% in the electric potential necessary to generate a clear band of trapped particles. The findings from this study provide a systematic approach toward the design of high performance iDEP devices for their lab-on-a-chip integration. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Dielectrophoretic gating and phase separation of particles for micro- and nano-fluidic biodetection applications

    NASA Astrophysics Data System (ADS)

    James, Conrad

    2006-03-01

    Performance metrics for biological detection systems are significantly impacted by their ability to separate target analytes from background materials, a process that aids in the elimination of false positives. We report here several implementations of an electro-hydrodynamic technique for separating analytes in nanoliter sample volumes. This technique, AC dielectrophoresis (DEP) accompanied by field-induced phase transitions, includes electric field- and shear-induced phenomena to modify local concentrations of suspended particles. This non-optical separation technique relies upon intrinsic electric polarizability, and thus requires no time-consuming and costly labeling steps. We have demonstrated biological and non-biological particle separation, and both batch-mode and continuous flow configurations have been developed. The dielectrophoretic gating technique has been optimized to produce large electric field gradients(∇E^2˜10^20V^2/m^3) and we are currently applying this technique for particle chaperone preconcentration and nucleic acid purification. For the first application, we have achieved 100x preconcentration factors and high efficiency particle valving with no degradation in flowrate. This technique will prove useful for bead-based assay systems utilizing packed beds or high throughput flow cytometry. In the second application, we have preconcentrated dsDNA target molecules, and shown that preconcentration of false-positive inducing ssDNA reporter oligonucleotides is negligible. This method can be integrated on-chip, providing a significant advantage over conventional off-chip purification technologies such as centrifugation and precipitation. We will also present our results in traveling wave DEP, a technique which utilizes phase-quadrature signals to preconcentrate and transport particles without the use of hydrodynamic forces.

  5. Dielectrophoretic lab-on-CMOS platform for trapping and manipulation of cells.

    PubMed

    Park, Kyoungchul; Kabiri, Shideh; Sonkusale, Sameer

    2016-02-01

    Trapping and manipulation of cells are essential operations in numerous studies in biology and life sciences. We discuss the realization of a Lab-on-a-Chip platform for dielectrophoretic trapping and repositioning of cells and microorganisms on a complementary metal oxide semiconductor (CMOS) technology, which we define here as Lab-on-CMOS (LoC). The LoC platform is based on dielectrophoresis (DEP) which is the force experienced by any dielectric particle including biological entities in non-uniform AC electrical field. DEP force depends on the permittivity of the cells, its size and shape and also on the permittivity of the medium and therefore it enables selective targeting of cells based on their phenotype. In this paper, we address an important matter that of electrode design for DEP for which we propose a three-dimensional (3D) octapole geometry to create highly confined electric fields for trapping and manipulation of cells. Conventional DEP-based platforms are implemented stand-alone on glass, silicon or polymers connected to external infrastructure for electronics and optics, making it bulky and expensive. In this paper, the use of CMOS as a platform provides a pathway to truly miniaturized lab-on-CMOS or LoC platform, where DEP electrodes are designed using built-in multiple metal layers of the CMOS process for effective trapping of cells, with built-in electronics for in-situ impedance monitoring of the cell position. We present electromagnetic simulation results of DEP force for this unique 3D octapole geometry on CMOS. Experimental results with yeast cells validate the design. These preliminary results indicate the promise of using CMOS technology for truly compact miniaturized lab-on-chip platform for cell biotechnology applications.

  6. The dielectrophoretic disassociation of chloride ions and the influence on diamagnetic anisotropy in cell membranes.

    PubMed

    Purnell, Marcy C; Skrinjar, Terence J

    2016-11-01

    Chloride channels represent ubiquitously expressed proteins that regulate fundamental cellular processes including membrane potential, maintenance of intracellular pH, and regulation of cell volume. However, mechanisms to modulate this large family of ion channels have remained elusive to date. This large chloride channel family does not appear to operate with selectivity similar to the sodium and potassium channels. These unique channels appear to be bi-directional cotransporters of two or more different molecules or ions across a bilayer phospholipid membrane. Here we show how 3 amperes of direct current from a device that generates an electromagnetic field in a 3 mM hypotonic saline solution leads to a dielectrophoretic disassociation of the chloride ion from its chloro-metabolites transforming it into a polymorphic diamagnetically disassociated bio-chloride (bCl-). This field treated aqueous solution appears to continue to induce a magnetic moment change in solution for some hours when no longer under the influence of the direct current; for when this field influenced solution is used to reconstitute growth media of human breast carcinoma (MDA-MB-231) and human breast epithelial (MCF-10A) cells in vitro, significant changes in chloride ion channel expression, membrane potential, cell volume, and a massive transcriptional reprogramming of 2,468 genes expressions by Human Genome U133 Plus 2.0 Gene Chip Array (Affymetrix) analyses occur. We will highlight how the strong changes in chloride ion channel expression and cell physiology could be intricately linked to enhanced diamagnetic anisotropy in cell membranes that occur under the influence of this disassociated polymorphic bCl-.

  7. An integrated acoustic and dielectrophoretic particle manipulation in a microfluidic device for particle wash and separation fabricated by mechanical machining

    PubMed Central

    Çetin, Barbaros; Özer, Mehmet Bülent; Çağatay, Erdem; Büyükkoçak, Süleyman

    2016-01-01

    In this study, acoustophoresis and dielectrophoresis are utilized in an integrated manner to combine the two different operations on a single polydimethylsiloxane (PDMS) chip in sequential manner, namely, particle wash (buffer exchange) and particle separation. In the washing step, particles are washed with buffer solution with low conductivity for dielectrophoretic based separation to avoid the adverse effects of Joule heating. Acoustic waves generated by piezoelectric material are utilized for washing, which creates standing waves along the whole width of the channel. Coupled electro-mechanical acoustic 3D multi-physics analysis showed that the position and orientation of the piezoelectric actuators are critical for successful operation. A unique mold is designed for the precise alignment of the piezoelectric materials and 3D side-wall electrodes for a highly reproducible fabrication. To achieve the throughput matching of acoustophoresis and dielectrophoresis in the integration, 3D side-wall electrodes are used. The integrated device is fabricated by PDMS molding. The mold of the integrated device is fabricated using high-precision mechanical machining. With a unique mold design, the placements of the two piezoelectric materials and the 3D sidewall electrodes are accomplished during the molding process. It is shown that the proposed device can handle the wash and dielectrophoretic separation successfully. PMID:26865905

  8. An integrated acoustic and dielectrophoretic particle manipulation in a microfluidic device for particle wash and separation fabricated by mechanical machining.

    PubMed

    Çetin, Barbaros; Özer, Mehmet Bülent; Çağatay, Erdem; Büyükkoçak, Süleyman

    2016-01-01

    In this study, acoustophoresis and dielectrophoresis are utilized in an integrated manner to combine the two different operations on a single polydimethylsiloxane (PDMS) chip in sequential manner, namely, particle wash (buffer exchange) and particle separation. In the washing step, particles are washed with buffer solution with low conductivity for dielectrophoretic based separation to avoid the adverse effects of Joule heating. Acoustic waves generated by piezoelectric material are utilized for washing, which creates standing waves along the whole width of the channel. Coupled electro-mechanical acoustic 3D multi-physics analysis showed that the position and orientation of the piezoelectric actuators are critical for successful operation. A unique mold is designed for the precise alignment of the piezoelectric materials and 3D side-wall electrodes for a highly reproducible fabrication. To achieve the throughput matching of acoustophoresis and dielectrophoresis in the integration, 3D side-wall electrodes are used. The integrated device is fabricated by PDMS molding. The mold of the integrated device is fabricated using high-precision mechanical machining. With a unique mold design, the placements of the two piezoelectric materials and the 3D sidewall electrodes are accomplished during the molding process. It is shown that the proposed device can handle the wash and dielectrophoretic separation successfully.

  9. Determination of size and element composition distributions of complex colloids by sedimentation field-flow fractionation—inductively coupled plasma mass spectrometry

    USGS Publications Warehouse

    Murphy, Deirdre M.

    1993-01-01

    Sedimentation field-flow fractionation (SdFFF) and inductively coupled plasma mass spectrometry (ICP-MS) have been directly combined and the resulting SdFFF-ICP-MS instrument can be used to produce element based size distributions of colloidal samples. Using appropriate tracer elements the size distributions of specific components can be picked out from a complex mixture. Changes in chemical composition of mixtures as a function of particle size can be readily monitored by plotting appropriate element atomic ratio distributions. These applications have been illustrated using data obtained with samples of the clay minerals kaolinite and illite and a natural suspended particulate matter from the Darling River (Australia).

  10. Dielectrophoretic manipulation of a biological and non-biological analytes in a microfluidic channel

    NASA Astrophysics Data System (ADS)

    Bennett, Dawn J.

    Micro-total-analytical systems (muTASs) for analyzing chemical/biological substances are now used across a wide variety of applications ranging from biological warfare agent detection to the healthcare industry. The first step in the operation of a muTAS consists of concentrating and separating the analytes of interest from the background matrix and positioning them into selected locations for subsequent analysis. The use of ac electric fields was demonstrated to have promising potential for a muTAS because the application of an ac field suppresses undesirable electrolytic effects in the liquid. The main purpose of this work is to study micro-scale phenomena in a flowing suspension subject to shear and high-gradient strong ac electric field. A microfluidic device equipped with dielectrophoretic gates arranged perpendicular to the flow was designed and fabricated at Sandia National Laboratories. Experiments were conducted on flowing suspensions over a broad range of flow and electric field parameters to investigate how these characteristics affect the concentration and separation of particles. It was found that dipolar interactions between suspended particles subject to a high-gradient ac field and shear lead to a new many-body phenomenon of dielectrophoresis accompanied by the field-induced phase separation in a flowing suspension. As a result, shear and electric stresses strongly compress a layer enriched with particles. The predictions of the proposed electro-hydrodynamic model for the coupled shear, dielectrophoresis, and phase separation in a flowing suspension are shown to be consistent with experimental data even though the model contains no fitting parameters. Both the model and the experiments showed that the concentration volume could be increased up to about 50%. It was demonstrated that the field-induced dielectrophoresis accompanied by the phase separation provides a new method for concentrating particles in focused regions and for separating biological

  11. Enhanced Dielectrophoretic Enrichment of Nanoparticles Using a Nanostructured Tip for Nanoengineered Medicine and Biology

    NASA Astrophysics Data System (ADS)

    Yeo, Woonhong

    2011-12-01

    Enrichment of low-concentration nanoparticles (NPs) is of great interest in the fields of medicine, biology, and environment. In particular, the enrichment of bioparticles such as virus, quantum dots, DNA, or protein can have broad impacts on disease diagnosis, drug discovery, and environmental monitoring. Currently available NP enrichment methods employ centrifugation, microfiltration, or magnetic field. However, these methods are limited in cumbersome preparation steps, low yield, and low throughput. Electric field-based methods have demonstrated potential for NP enrichment, but two-dimensional planar electrodes are limited in sensitivity, molecular transfer, and imaging capability. In addition, the detection of low abundance, non-amplifiable particles such as proteins and metals is very challenging due to the low efficiency of current methods. In this dissertation, the challenges are addressed by nanotip-based NP enrichment. Fundamentals of NP enrichment are studied with a nanostructured tip. The nanotip-based NP enrichment is investigated by correlating a dielectrophoretic (DEP) force with Brownian motion force. In experiment, the predicted NP enrichment is validated by using gold (Au) NPs. The DEP effective distance for NP enrichment with a nanotip is suggested. Sequence-specific enrichment of oligonucleotides is studied by considering DEP force, Brownian motion, and affinity binding. In experiment, the optimal parameters for ultimate enrichment performance are studied using a hybridization assay. In the assay, a nanotip is functionalized with probe-oligonucleotides for sequence-specific binding. Size-specific NP enrichment is explored by studying DEP, capillary action, and viscosity. The capillary action force with a nanotip is calculated analytically, which is then compared with the DEP force. The viscosity effect is considered for NP capturing on a nanotip. The studied size-specific enrichment mechanism is validated in experiment by using various

  12. The development of malaria diagnostic techniques: a review of the approaches with focus on dielectrophoretic and magnetophoretic methods.

    PubMed

    Kasetsirikul, Surasak; Buranapong, Jirayut; Srituravanich, Werayut; Kaewthamasorn, Morakot; Pimpin, Alongkorn

    2016-07-12

    The large number of deaths caused by malaria each year has increased interest in the development of effective malaria diagnoses. At the early-stage of infection, patients show non-specific symptoms or are asymptomatic, which makes it difficult for clinical diagnosis, especially in non-endemic areas. Alternative diagnostic methods that are timely and effective are required to identify infections, particularly in field settings. This article reviews conventional malaria diagnostic methods together with recently developed techniques for both malaria detection and infected erythrocyte separation. Although many alternative techniques have recently been proposed and studied, dielectrophoretic and magnetophoretic approaches are among the promising new techniques due to their high specificity for malaria parasite-infected red blood cells. The two approaches are discussed in detail, including their principles, types, applications and limitations. In addition, other recently developed techniques, such as cell deformability and morphology, are also overviewed in this article.

  13. Quantitative In Vitro Assessment of Liposome Stability and Drug Transfer Employing Asymmetrical Flow Field-Flow Fractionation (AF4).

    PubMed

    Holzschuh, Stephan; Kaeß, Kathrin; Fahr, Alfred; Decker, Christiane

    2016-04-01

    In the present study we introduce an efficient approach for a size-based separation of liposomes from plasma proteins employing AF4. We investigated vesicle stability and release behavior of the strongly lipophilic drug temoporfin from liposomes in human plasma for various incubation times at 37°C. We used the radioactive tracer cholesteryl oleyl ether (COE) or dipalmitoyl-phosphocholine (DPPC) as lipid markers and (14)C-labeled temoporfin. First, both lipid labels were examined for their suitability as liposome markers. Furthermore, the influence of plasma origin on liposome stability and drug transfer was investigated. The effect of membrane fluidity and PEGylation on vesicle stability and drug release characteristics was also analyzed. Surprisingly, we observed an enzymatic transfer of (3)H-COE to lipoproteins due to the cholesterol ester transfer protein (CETP) in human plasma in dependence on membrane rigidity and were able to inhibit this transfer by plasma preincubation with the CETP inhibitor torcetrapib. This effect was not seen when liposomes were incubated in rat plasma. DPPC labels suffered from hydrolysis effects during preparation and/or storage. Fluid liposomes were less stable in human plasma than their PEGylated analogues or a rigid formulation. In contrast, the transfer of the incorporated drug to lipoproteins was higher for the rigid formulations. The observed effects render COE-labels questionable for in vivo studies using CEPT-rich species. Here, choline labelled (14)C-DPPC was found to be the most promising alternative. Bilayer composition has a high influence on stability and drug release of a liposomal formulation in human plasma.

  14. Different elution modes and field programming in gravitational field-flow fractionation: field programming using density and viscosity gradients.

    PubMed

    Plocková, Jana; Chmelík, Josef

    2006-06-23

    In previous papers, several approaches to programming of the resulting force field in GFFF were described and investigated. The experiments were dealing with flow-velocity and channel thickness, i.e. factors influencing hydrodynamic lift forces (HLF). The potential of density and viscosity of carrier liquid for field programming was predicted and demonstrated by preliminary experiments. This work is devoted to experimental verification of the influence of carrier liquid density and viscosity. Several carrier liquid density and simultaneously viscosity gradients using water-methanol mixtures are in this work implemented in the separation of a model silica mixture. Working with the water-methanol gradients, one is not able to separate the influence of density from the contribution of viscosity. However, we found experimental conditions to show the isolated effect of carrier liquid density (two water-methanol mixtures of equal viscosity differing in their densities). In order to demonstrate the isolated effect of viscosity, we implemented in this work a new system of (hydroxypropyl)methyl cellulose (HPMC) carrier liquids. Three different HPMC compositions enabled to vary the viscosity more than two times at almost constant density. With increasing carrier liquid viscosity, the focusing and elevating trend was clearly pronounced for 5 and 10 microm silica particles. By the isolated effect of increased viscosity, the centre of the 10 microm particle zone was elevated to the streamline at 16% of the channel height. These experiments have shown that the influence of carrier liquid viscosity on HLF should be taken into account even at higher levels above the channel bottom, i.e. beyond the near-wall region. Further, it is shown that higher value of carrier liquid viscosity improves the separation of the model mixture in terms of time and resolution.

  15. Numerical investigation of 22 seconds of convection under the effect of dielectrophoretic force in an annular gap

    NASA Astrophysics Data System (ADS)

    Crumeyrolle, Olivier; Egbers, Christoph; Mutabazi, Innocent; Dahley, M. Norman; Smieszek, Marlene

    2012-07-01

    We investigate numerically the thermal convection of an annular dielectric liquid sheet under the effect of the dielectrophoretic force, as observed when a dielectric liquid is permeated by an inhomogeneous electric field. This is of particular interest for space applications as natural convection cannot appear and forced convection from moving parts such as pumps is undesirable due to the expected wearing and lower reliability. Hence heat exchanger relying on the dielectrophoretic force to create convection could provide light, compact and reliable heat exchanger for aerospace cooling systems \\cite{crumeyrolleP}. We investigate the case of a radius ratio equal to 0.5 and Prandtl number of 65. This setup is under experimental investigation at LAS, BTU Cottbus, both on ground and during parabolic flight. The 3D linear stability analysis, that takes the finite size of the system into account, shows that the critical mode is non-axisymmetric and under the form of two counteroriented helices, rather than under the form of rolls as predicted in past investigations\\cite{crumeyrolleT}. Due to the short duration of microgravity during parabolic flight (22 seconds), 3D time-dependent DNS are required with realistic initial conditions. The simulations show that the helices are difficult to observe, as the flow pattern is dominated by convection plumes. We report that transient thermal transfer at the inner cylinder is strongly enhanced by those structures, while the thermal transfer close to the outer cylinder is weaker. J.S. Paschkewitz and {D.M.} Pratt, Exp. Therm. Fluid Sci., 21,, 187 (2000). M. Takashima, Q. J. Mech. appl. Math. 33,, 93 (1980).

  16. Numerical studies of manipulation and separation of Janus particles in nano-orifice based DC-dielectrophoretic microfluidic chips

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Li, Dongqing

    2017-09-01

    The direct current dielectrophoretic (DC-DEP) manipulation and separation of polystyrene-based Janus particles and the homogeneous polystyrene particles in microchannels are numerically investigated. To induce the DEP force, a small electric potential difference is applied across the microchannel via a smaller nano-orifice on one side of the channel walls and a larger micro-orifice on the opposite channel wall. A strong non-uniform electric field gradient is generated by the asymmetric orifices, and the particles will undergo the DEP forces when moving with the flow through the vicinity of the small orifice, where the strongest electrical field gradient exists. By adjusting the electrical conductivity of the suspending solution, one kind of the particles will experience the negative DEP force while another will undergo the positive DEP force. In this way, the separation of 5 µm Janus particles and homogeneous polystyrene particles, and the separation of 3 µm and 5 µm Janus particles were numerically demonstrated. Moreover, in order to further understand the dielectrophoretic motion of the Janus particles, the DC-DEP force on the Janus particles was analyzed and the effects of the electric fields, as well as the coating coverage, thickness, and electric conductivity of the Janus particles were studied. The results show that the Janus particles with gold coating coverage over 50% will experience positive DEP forces and be attracted towards the maximum electric fields. It is also found that the effect of the gold coating thickness of the Janus particles on their trajectories can be neglected when using the DC-DEP method.

  17. Fractional randomness

    NASA Astrophysics Data System (ADS)

    Tapiero, Charles S.; Vallois, Pierre

    2016-11-01

    The premise of this paper is that a fractional probability distribution is based on fractional operators and the fractional (Hurst) index used that alters the classical setting of random variables. For example, a random variable defined by its density function might not have a fractional density function defined in its conventional sense. Practically, it implies that a distribution's granularity defined by a fractional kernel may have properties that differ due to the fractional index used and the fractional calculus applied to define it. The purpose of this paper is to consider an application of fractional calculus to define the fractional density function of a random variable. In addition, we provide and prove a number of results, defining the functional forms of these distributions as well as their existence. In particular, we define fractional probability distributions for increasing and decreasing functions that are right continuous. Examples are used to motivate the usefulness of a statistical approach to fractional calculus and its application to economic and financial problems. In conclusion, this paper is a preliminary attempt to construct statistical fractional models. Due to the breadth and the extent of such problems, this paper may be considered as an initial attempt to do so.

  18. Rapid 3D Refractive‐Index Imaging of Live Cells in Suspension without Labeling Using Dielectrophoretic Cell Rotation

    PubMed Central

    Habaza, Mor; Kirschbaum, Michael; Guernth‐Marschner, Christian; Dardikman, Gili; Barnea, Itay; Korenstein, Rafi; Duschl, Claus

    2016-01-01

    A major challenge in the field of optical imaging of live cells is achieving rapid, 3D, and noninvasive imaging of isolated cells without labeling. If successful, many clinical procedures involving analysis and sorting of cells drawn from body fluids, including blood, can be significantly improved. A new label‐free tomographic interferometry approach is presented. This approach provides rapid capturing of the 3D refractive‐index distribution of single cells in suspension. The cells flow in a microfluidic channel, are trapped, and then rapidly rotated by dielectrophoretic forces in a noninvasive and precise manner. Interferometric projections of the rotated cell are acquired and processed into the cellular 3D refractive‐index map. Uniquely, this approach provides full (360°) coverage of the rotation angular range around any axis, and knowledge on the viewing angle. The experimental demonstrations presented include 3D, label‐free imaging of cancer cells and three types of white blood cells. This approach is expected to be useful for label‐free cell sorting, as well as for detection and monitoring of pathological conditions resulting in cellular morphology changes or occurrence of specific cell types in blood or other body fluids. PMID:28251046

  19. Dielectric elastomer actuators of silicone rubber-titanium dioxide composites obtained by dielectrophoretic assembly of filler particles

    NASA Astrophysics Data System (ADS)

    Javadi, S.; Razzaghi-Kashani, M.

    2010-04-01

    Formation of controlled morphology of fillers in polymeric composites may be difficult to achieve by conventional methods such as mechanical shear or chemical methods. Tunable structure of filler and anisotropic properties in composites can be obtained by exploiting dielectrophoretic assembly of fillers in a polymer composite by using electric fields. In this study, different concentrations of Titanium Dioxide (TiO2) particles in silicone rubber matrix were assembled in a chain-like structure by using an alternating electric field. Silicone rubber matrix was vulcanized to transform the liquid to solid and maintain the filler structure in the desired direction. Generation of chain structure of filler was verified by Scanning Electron Microscopy (SEM) and equilibrium swelling. It was shown that dielectric permittivity of the oriented composite is higher whereas its dielectric loss factor is lower in the orientation (thickness) direction than those for the composites with random distribution of filler. This phenomenon was in agreement with results of dynamic-mechanical loss factor for these composites, and can be utilized in more efficient dielectric elastomer actuators. Elastic modulus is higher for the structured samples, but presence of titania filler induced a softening effect at higher strains where the actuators are practically being pre-stretched. A critical concentration of filler was distinguished as the percolation point at which the change in dielectric behavior is amplified. Using a simple blocking-force measurement, potential advantages of structured composites over the ones with randomly-distributed filler was explained for potential dielectric elastomer actuator applications.

  20. Enhanced sub-micron colloidal particle separation with interdigitated microelectrode arrays using mixed AC/DC dielectrophoretic scheme.

    PubMed

    Swaminathan, Vikhram V; Shannon, Mark A; Bashir, Rashid

    2015-04-01

    Dielectrophoretic separation of particles finds a variety of applications in the capture of species such as cells, viruses, proteins, DNA from biological systems, as well as other organic and inorganic contaminants from water. The ability to capture particles is constrained by poor volumetric scaling of separation force with respect to particle diameter, as well as the weak penetration of electric fields in the media. In order to improve the separation of sub-micron colloids, we present a scheme based on multiple interdigitated electrode arrays under mixed AC/DC bias. The use of high frequency longitudinal AC bias breaks the shielding effects through electroosmotic micromixing to enhance electric fields through the electrolyte, while a transverse DC bias between the electrode arrays enables penetration of the separation force to capture particles from the bulk of the microchannel. We determine the favorable biasing conditions for field enhancement with the help of analytical models, and experimentally demonstrate the improved capture from sub-micron colloidal suspensions with the mixed AC/DC electrostatic excitation scheme over conventional AC-DEP methods.

  1. On-chip SERS analysis for single mimic pathogen detection using Raman-labeled nanoaggregate-embedded beads with a dielectrophoretic chip

    NASA Astrophysics Data System (ADS)

    Huang, Chen-Han; Lin, Hsing-Ying; Kuo, I.-Ting; Hsieh, Wen-Hsin; Huang, Ping-Ji; Yang, Tzyy-Schiuan; Chau, Lai-Kwan

    2012-02-01

    The integration of Raman-labeled nanoaggregate-embedded beads (NAEBs) for high performance SERS analysis of single mimic pathogen on a self-designed dielectrophoretic chip is demonstrated. The Raman tags called NAEBs are silica-coated, dye-induced aggregates of a small number of gold nanoparticles (AuNPs). In this work, NAEBs consisting of a Raman dye tetramethyl-rhodamine-5-isothiosyanate (TRITC) are chemically functionalized with streptavidin to detect biotin-functionalized polystyrene (PS) microspheres which mimic as pathogens. The sample solution of completely mixed streptavidin-functionalized NAEBs and biotin-functionalized PS microspheres is pumped into the microfluidic channel of a dielectrophoretic chip. By giving an AC voltage on the embedded electrodes, a single mimic pathogen can be caught via the non-contact dielectrophoretic force and suspended at the central cross of four aluminum electrodes for subsequent Raman spectroscopic detection. The SERS signal of TRITC is used as a spectral signature of specific mimic pathogen recognition, otherwise only the background Raman signal of a PS microsphere is observed. A pathogen-specific biosensor based on the dielectrophoresis-Raman spectroscopy system is developed, and the proof-ofconcept is confirmed by the specific molecular interaction model of streptavidin with biotin. Therefore, the on-chip multiplex SERS analysis of pathogens can be anticipated by employing different dye-tagged NAEBs simultaneously in a sample solution. We believe this bioassay has the ability to screen and detect multiple pathogens with minimal sample processing and handling even a small number of pathogens is present.

  2. Gravitational Effects on Near Field Flow Structure of Low Density Gas Jets

    NASA Technical Reports Server (NTRS)

    Yep, Tze-Wing; Agrawal, Ajay K.; Griffin, DeVon; Salzman, Jack (Technical Monitor)

    2001-01-01

    Experiments were conducted in Earth gravity and microgravity to acquire quantitative data on near field flow structure of helium jets injected into air. Microgravity conditions were simulated in the 2.2-second drop tower at NASA Glenn Research Center. The jet flow was observed by quantitative rainbow schlieren deflectometry, a non-intrusive line of site measurement technique for the whole field. The flow structure was characterized by distributions of angular deflection and helium mole percentage obtained from color schlieren images taken at 60 Hz. Results show that the jet flow was significantly influenced by the gravity. The jet in microgravity was up to 70 percent wider than that in Earth gravity. The jet flow oscillations observed in Earth gravity were absent in microgravity, providing direct experimental evidence that the flow instability in the low density jet was buoyancy induced. The paper provides quantitative details of temporal flow evolution as the experiment undergoes a change in gravity in the drop tower.

  3. Gravitational Effects on Near Field Flow Structure of Low Density Gas Jets

    NASA Technical Reports Server (NTRS)

    Griffin, D. W.; Yep, T. W.; Agrawal, A. K.

    2005-01-01

    Experiments were conducted in Earth gravity and microgravity to acquire quantitative data on near field flow structure of helium jets injected into air. Microgravity conditions were simulated in the 2.2- second drop tower at NASA Glenn Research Center. The jet flow was observed by quantitative rainbow schlieren deflectometry, a non-intrusive line of site measurement technique for the whole field. The flow structure was characterized by distributions of angular deflection and helium mole percentage obtained from color schlieren images taken at 60 Hz. Results show that the jet in microgravity was up to 70 percent wider than that in Earth gravity. The global jet flow oscillations observed in Earth gravity were absent in microgravity, providing direct experimental evidence that the flow instability in the low density jet was buoyancy induced. The paper provides quantitative details of temporal flow evolution as the experiment undergoes change in gravity in the drop tower.

  4. Size and medium conductivity dependence on dielectrophoretic behaviors of gas core poly-L-lysine shell nanoparticles.

    PubMed

    Yang, Chungja; Wu, Chun-Jen; Ostafin, Agnes E; Thibaudeau, Giselle; Minerick, Adrienne R

    2015-04-01

    Dynamic (dis)assembly of biocompatible nanoparticles into 3D, packed structures would benefit drug delivery, films, and diagnostics. Dielectrophoretic (DEP) microdevices can rapidly assemble and manipulate polarizable particles within nonuniform electric fields. DEP has primarily discerned micrometer particles since nanoparticles experience smaller forces. This work examines conductivity and size DEP dependencies of previously unexplored spherical core-shell nanoparticle (CSnp) into 3D particle assemblies. Poly-L-lysine shell material was custom synthesized around a gas core to form CSnps. DEP frequencies from 1 kHz to 80 MHz at fixed 5 volts peak-to-peak and medium conductivities of 10(-5) and 10(-3) S/m were tested. DEP responses of ∼220 and ∼400 nm poly-L-lysine CSnps were quantified via video intensity densitometry at the microdevice's quadrapole electrode center for negative DEP (nDEP) and adjacent to electrodes for positive DEP. Intensity densitometry was then translated into a relative DEP response curve. An unusual nDEP peak occurred at ∼57 MHz with 25-80 times greater apparent nDEP force. All electrical circuit components were then impedance matched, which changed the observed response to weak positive DEP at low frequencies and consistently weak nDEP from ∼100 kHz to 80 MHz. This impedance-matched behavior agrees with conventional Clausius-Mossotti DEP signatures taking into account the gas core's contributions to the polarization mechanisms. This work describes a potential pitfall when conducting DEP at higher frequencies in microdevices and concurrently demonstrates nDEP behavior for a chemically and structurally distinct particle system. This work provides insight into organic shell material properties in nanostructures and strategies to facilitate dynamic nanoparticle assemblies.

  5. Numerical modelling and measurement of cell trajectories in 3-D under the influence of dielectrophoretic and hydrodynamic forces.

    PubMed

    Holzner, Felix; Hagmeyer, Britta; Schütte, Julia; Kubon, Massimo; Angres, Brigitte; Stelzle, Martin

    2011-09-01

    This research is part of a program aiming at the development of a fluidic microsystem for in vitro drug testing. For this purpose, primary cells need to be assembled to form cellular aggregates in such a way as to resemble the basic functional units of organs. By providing for in vivo-like cellular contacts, proper extracellular matrix interaction and medium perfusion it is expected that cells will retain their phenotype over prolonged periods of time. In this way, in vitro test systems exhibiting in vivo type predictivity in drug testing are envisioned. Towards this goal a 3-D microstructure micro-milled in a cyclic olefin copolymer (COC) was designed in such a way as to assemble liver cells via insulator-based dielectrophoresis (iDEP) in a sinusoid-type fashion. First, numeric modelling and simulation of dielectrophoretic and hydrodynamic forces acting on cells in this microsystem was performed. In particular, the problem of the discontinuity of the electric field at the interface between the fluid media in the system and the polymer materials it consists of was addressed. It was shown that in certain cases, the material of the microsystem may be neglected altogether without introducing considerable error into the numerical solution. This simplification enabled the simulation of 3-D cell trajectories in complex chip geometries. Secondly, the assembly of HepG2 cells by insulator-based dielectrophoresis in this device is demonstrated. Finally, theoretical results were validated by recording 3-D cell trajectories and the Clausius-Mossotti factor of liver cells was determined by combining results obtained from both simulation and experiment.

  6. Modeling and simulation of dielectrophoretic collective dynamics in a suspension of polarizable particles under the action of a gradient AC electric field.

    PubMed

    Tada, Shigeru; Shen, Yan; Qiu, Zhiyong

    2017-06-01

    When a suspension of polarizable particles is subjected to a gradient AC electric field, the particles exhibit collective motion due to an interaction between the dipole induced in the particles and the spatial gradient of the electric field; this is known as dielectrophoresis. In the present study, the collective dynamics of suspended particles in a parallel-plate electric chamber was investigated by simulating numerically the trajectories of individual particles under the action of combined dielectrophoretic and dipole-dipole interparticle forces. The particles were transported by the dielectrophoretic forces toward the grounded electrodes. Before long, when the particles approached the site of the minimum field strength, attractive/repulsive interparticle forces became dominant and acted among the particles attempting to form a column-like cluster, having the particles distribution in concentric circles in its cross-section, in line with the centerline of the grounded electrodes. Our results also well reproduced the transient particle aggregation that was observed experimentally. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Dynamic drag force based on iterative density mapping: A new numerical tool for three-dimensional analysis of particle trajectories in a dielectrophoretic system.

    PubMed

    Knoerzer, Markus; Szydzik, Crispin; Tovar-Lopez, Francisco Javier; Tang, Xinke; Mitchell, Arnan; Khoshmanesh, Khashayar

    2016-02-01

    Dielectrophoresis is a widely used means of manipulating suspended particles within microfluidic systems. In order to efficiently design such systems for a desired application, various numerical methods exist that enable particle trajectory plotting in two or three dimensions based on the interplay of hydrodynamic and dielectrophoretic forces. While various models are described in the literature, few are capable of modeling interactions between particles as well as their surrounding environment as these interactions are complex, multifaceted, and computationally expensive to the point of being prohibitive when considering a large number of particles. In this paper, we present a numerical model designed to enable spatial analysis of the physical effects exerted upon particles within microfluidic systems employing dielectrophoresis. The model presents a means of approximating the effects of the presence of large numbers of particles through dynamically adjusting hydrodynamic drag force based on particle density, thereby introducing a measure of emulated particle-particle and particle-liquid interactions. This model is referred to as "dynamic drag force based on iterative density mapping." The resultant numerical model is used to simulate and predict particle trajectory and velocity profiles within a microfluidic system incorporating curved dielectrophoretic microelectrodes. The simulated data are compared favorably with experimental data gathered using microparticle image velocimetry, and is contrasted against simulated data generated using traditional "effective moment Stokes-drag method," showing more accurate particle velocity profiles for areas of high particle density.

  8. Fractional distillation

    SciTech Connect

    Brand, M. J.; Callejas, R. J.

    1985-10-08

    Process and apparatus are provided for the recovery of low, medium and high boiling components from feed streams containing same wherein reboiler fouling, gumming and the like are minimized, via the control of fractionator reboiler temperatures.

  9. Fractionalize this

    SciTech Connect

    Phillips, Philip

    2010-12-01

    Precisely what are the electrons in a high-temperature superconductor doing before they superconduct? Strong electronic correlations may give rise to composite rather than fractionalized excitations, as is typical in other strongly coupled systems such as quark matter.

  10. Effect of Gravity on the Near Field Flow Structure of Helium Jet in Air

    NASA Technical Reports Server (NTRS)

    Agrawal, Ajay K.; Parthasarathy, Ramkumar; Griffin, DeVon

    2002-01-01

    Experiments have shown that a low-density jet injected into a high-density surrounding medium undergoes periodic oscillations in the near field. Although the flow oscillations in these jets at Richardson numbers about unity are attributed to the buoyancy, the direct physical evidence has not been acquired in the experiments. If the instability were indeed caused by buoyancy, the near-field flow structure would undergo drastic changes upon removal of gravity in the microgravity environment. The present study was conducted to investigate this effect by simulating microgravity environment in the 2.2-second drop tower at the NASA Glenn Research Center. The non-intrusive, rainbow schlieren deflectometry technique was used for quantitative measurements of helium concentrations in buoyant and non-buoyant jets. Results in a steady jet show that the radial growth of the jet shear layer in Earth gravity is hindered by the buoyant acceleration. The jet in microgravity was 30 to 70 percent wider than that in Earth gravity. The microgravity jet showed typical growth of a constant density jet shear layer. In case of a self-excited helium jet in Earth gravity, the flow oscillations continued as the jet flow adjusted to microgravity conditions in the drop tower. The flow oscillations were however not present at the end of the drop when steady microgravity conditions were reached.

  11. Understanding Multiplication of Fractions.

    ERIC Educational Resources Information Center

    Sweetland, Robert D.

    1984-01-01

    Discussed the use of Cuisenaire rods in teaching the multiplication of fractions. Considers whole number times proper fraction, proper fraction multiplied by proper fraction, mixed number times proper fraction, and mixed fraction multiplied by mixed fractions. (JN)

  12. ApoStream™, a new dielectrophoretic device for antibody independent isolation and recovery of viable cancer cells from blood

    PubMed Central

    Gupta, Vishal; Jafferji, Insiya; Garza, Miguel; Melnikova, Vladislava O.; Hasegawa, David K.; Pethig, Ronald; Davis, Darren W.

    2012-01-01

    Isolation and enumeration of circulating tumor cells (CTCs) are used to monitor metastatic disease progression and guide cancer therapy. However, currently available technologies are limited to cells expressing specific cell surface markers, such as epithelial cell adhesion molecule (EpCAM) or have limited specificity because they are based on cell size alone. We developed a device, ApoStream™ that overcomes these limitations by exploiting differences in the biophysical characteristics between cancer cells and normal, healthy blood cells to capture CTCs using dielectrophoretic technology in a microfluidic flow chamber. Further, the system overcomes throughput limitations by operating in continuous mode for efficient isolation and enrichment of CTCs from blood. The performance of the device was optimized using a design of experiment approach for key operating parameters such as frequency, voltage and flow rates, and buffer formulations. Cell spiking studies were conducted using SKOV3 or MDA-MB-231 cell lines that have a high and low expression level of EpCAM, respectively, to demonstrate linearity and precision of recovery independent of EpCAM receptor levels. The average recovery of SKOV3 and MDA-MB-231 cancer cells spiked into approximately 12 × 106 peripheral blood mononuclear cells obtained from 7.5 ml normal human donor blood was 75.4% ± 3.1% (n = 12) and 71.2% ± 1.6% (n = 6), respectively. The intra-day and inter-day precision coefficients of variation of the device were both less than 3%. Linear regression analysis yielded a correlation coefficient (R2) of more than 0.99 for a spiking range of 4–2600 cells. The viability of MDA-MB-231 cancer cells captured with ApoStream was greater than 97.1% and there was no difference in cell growth up to 7 days in culture compared to controls. The ApoStream device demonstrated high precision and linearity of recovery of viable cancer cells independent of their EpCAM expression level. Isolation

  13. Mystery Fractions

    ERIC Educational Resources Information Center

    Bhattacharyya, Sonalee; Namakshi, Nama; Zunker, Christina; Warshauer, Hiroko K.; Warshauer, Max

    2016-01-01

    Making math more engaging for students is a challenge that every teacher faces on a daily basis. These authors write that they are constantly searching for rich problem-solving tasks that cover the necessary content, develop critical-thinking skills, and engage student interest. The Mystery Fraction activity provided here focuses on a key number…

  14. Mystery Fractions

    ERIC Educational Resources Information Center

    Bhattacharyya, Sonalee; Namakshi, Nama; Zunker, Christina; Warshauer, Hiroko K.; Warshauer, Max

    2016-01-01

    Making math more engaging for students is a challenge that every teacher faces on a daily basis. These authors write that they are constantly searching for rich problem-solving tasks that cover the necessary content, develop critical-thinking skills, and engage student interest. The Mystery Fraction activity provided here focuses on a key number…

  15. Pitch Fractionation.

    DTIC Science & Technology

    1981-12-15

    13 3. Solvent Fractionation Experiments .................................... 15 4. Fourier Transform Infrared Spectra for A240 Petrolem Pitch AG 12...34 and Mesophase Pitch AG 164B ............................... 21 5. Fourier Transform Infrared Spectra ................................... 23 6...compared by Fourier transform infrared (FTIR) analysis using a Digilab Model FTS 14 spectrophotometer (Rockwell International, Anaheim, California

  16. Fraction Reduction through Continued Fractions

    ERIC Educational Resources Information Center

    Carley, Holly

    2011-01-01

    This article presents a method of reducing fractions without factoring. The ideas presented may be useful as a project for motivated students in an undergraduate number theory course. The discussion is related to the Euclidean Algorithm and its variations may lead to projects or early examples involving efficiency of an algorithm.

  17. Fraction Reduction through Continued Fractions

    ERIC Educational Resources Information Center

    Carley, Holly

    2011-01-01

    This article presents a method of reducing fractions without factoring. The ideas presented may be useful as a project for motivated students in an undergraduate number theory course. The discussion is related to the Euclidean Algorithm and its variations may lead to projects or early examples involving efficiency of an algorithm.

  18. Isotope fractionation

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    A rash of new controversy has emerged around the subject of mass-independent isotope fractionation effects, particularly in the case of the oxygen isotopes. To be sure, the controversy has been around for awhile, but it has been given new impetus by the results of a recent study by Mark H. Thiemens and John E. Heidenreich III of the University of California, San Diego (Science, March 4, 1983).Gustav Arrhenius has been trying to convince the planetary science community that chemical effects in isotope fractionation processes could explain observations in meteorites that appear to be outside of the traditionally understood mass-dependent fractionations (G. Arrhenius, J . L. McCrumb, and N. F. Friedman, Astrophys. Space Sci, 65, 297, 1974). Robert Clayton had made the basic observations of oxygen in carbonaceous chondrites that the slope of the δ17 versus δ18 line was 1 instead of the slope of ½ characteristic of terrestrial rocks and lunar samples (Ann. Rev. Nucl. Part. Sci., 28, 501, 1978). The mass-independent effects were ascribed to the apparent contribution of an ancient presolar system component of O16.

  19. Energy Production Calculations with Field Flow Models and Windspeed Predictions with Statistical Methods

    NASA Astrophysics Data System (ADS)

    Rüstemoǧlu, Sevinç; Barutçu, Burak; Sibel Menteş, Å.ž.

    2010-05-01

    The continuous usage of fossil fuels as primary energy source is the reason of the emission of CO and powerless economy of the country affected by the great flactuations in the unit price of energy sources. In recent years, developments in wind energy sector and the supporting new renewable energy policies of the countries allow the new wind farm owners and the firms who expect to be an owner to consider and invest on the renewable sources. In this study, the annual production of the turbines with 1.8 kW and 30 kW which are available for Istanbul Technical University in Energy Institute is calculated by Wasp and WindPro Field Flow Models and the wind characteristics of the area are analysed. The meteorological data used in calculation includes the period between 02.March.2000 and 31.May.2004 and is taken from the meteorological mast ( ) in Istanbul Technical University's campus area. The measurement data is taken from 2 m and 10 m heights with hourly means. The topography, roughness classes and shelter effects are defined in the models to make accurate extrapolation to the turbine sites. As an advantage, the region is nearly 3.5 km close to the Istanbul Bosphorous but as it can be seen from the Wasp and WindPro Model Results, the Bosphorous effect is interrupted by the new buildings and hight forestry. The shelter effect of these high buildings have a great influence on the wind flow and decrease the high wind energy potential which is produced by the Bosphorous effect. This study, which determines wind characteristics and expected annual production, is important for this Project Site and therefore gains importance before the construction of wind energy system. However, when the system is operating, developing the energy management skills, forecasting the wind speed and direction will become important. At this point, three statistical models which are Kalman Fitler, AR Model and Neural Networks models are used to determine the success of each method for correct

  20. Asymmetric Flow-Field Flow Fractionation (AF4) of Aqueous C60 Aggregates with Dynamic Light Scattering Size and LC-MS

    EPA Science Inventory

    Current methods for the size determination of nanomaterials in aqueous suspension include dynamic or static light scattering and electron or atomic force microscopy techniques. Light scattering techniques are limited by poor resolution and the scattering intensity dependence on p...

  1. Asymmetric Flow-Field Flow Fractionation (AF4) of Aqueous C60 Aggregates with Dynamic Light Scattering Size and LC-MS

    EPA Science Inventory

    Current methods for the size determination of nanomaterials in aqueous suspension include dynamic or static light scattering and electron or atomic force microscopy techniques. Light scattering techniques are limited by poor resolution and the scattering intensity dependence on p...

  2. Size Determination of Aqueous C60 by Asymmetric Flow Field-Flow Fractionation (AF4) and in-Line Dynamic Light Scattering

    EPA Science Inventory

    To date, studies on the environmental behaviour of aggregated aqueous fullerene nanomaterials have used the entire size distribution of fullerene aggregates and do not distinguish between different aggregate size classes. This is a direct result of the lack of analytical methods ...

  3. Size Determination of Aqueous C60 by Asymmetric Flow Field-Flow Fractionation (AF4) and in-Line Dynamic Light Scattering

    EPA Science Inventory

    To date, studies on the environmental behaviour of aggregated aqueous fullerene nanomaterials have used the entire size distribution of fullerene aggregates and do not distinguish between different aggregate size classes. This is a direct result of the lack of analytical methods ...

  4. Asymmetric Flow Field Flow Fractionation Online with Single Particle – Inductively Coupled Plasma Mass Spectrometry: Detection and Quantification of Silver Nanoparticles in Aqueous Samples

    EPA Science Inventory

    Silver nanoparticles (AgNPs) are increasingly being used in many consumer products as disinfectants. Through the use of these products, AgNPs could likely enter aquatic environments. Because recent studies have shown that AgNPs are toxic to various species, including microorgan...

  5. Asymmetric Flow Field Flow Fractionation Online with Single Particle – Inductively Coupled Plasma Mass Spectrometry: Detection and Quantification of Silver Nanoparticles in Aqueous Samples

    EPA Science Inventory

    Silver nanoparticles (AgNPs) are increasingly being used in many consumer products as disinfectants. Through the use of these products, AgNPs could likely enter aquatic environments. Because recent studies have shown that AgNPs are toxic to various species, including microorgan...

  6. Selective nanomanipulation of fluorescent polystyrene nano-beads and single quantum dots at gold nanostructures based on the AC-dielectrophoretic force

    NASA Astrophysics Data System (ADS)

    Kim, Jinsik; Hwang, Kyo Seon; Lee, Sangyoup; Park, Jung Ho; Shin, Hyun-Joon

    2015-11-01

    We introduced the selective manipulation of polystyrene (PS) nano-beads and single quantum dots (QDs) at a gold nanostructure by using the AC-dielectrophoretic (DEP) force. Manipulation in three degrees of freedom (end-facet, side, and position-selective manipulation) was accomplished in gold nanostructures between microelectrodes. A 10 μm gap between the microelectrodes, which has a 100 nm-wide nanowire and 200 nm-wide vortex nanostructures at the inside of the gap, was fabricated, and nanostructures were not connected with the electrodes. We also performed theoretical calculations to verify the selective manipulation through the floating AC-DEP force. A sufficiently high gradient of the square of the electric field (∇|E|2, ~1019 V2 m-3) was accomplished and controlled for achieving a strong attaching force of nanoparticles using the gap between microelectrodes and nanostructures as well as the rotation of structures. Fluorescent PS nano-beads and QDs were attached at the designed end facet, side, and position of nanostructures with high selectivity. A single QD attachment was also realized at gold nanostructures, and the attached QDs were verified as single using optical ``blinking'' measurements.We introduced the selective manipulation of polystyrene (PS) nano-beads and single quantum dots (QDs) at a gold nanostructure by using the AC-dielectrophoretic (DEP) force. Manipulation in three degrees of freedom (end-facet, side, and position-selective manipulation) was accomplished in gold nanostructures between microelectrodes. A 10 μm gap between the microelectrodes, which has a 100 nm-wide nanowire and 200 nm-wide vortex nanostructures at the inside of the gap, was fabricated, and nanostructures were not connected with the electrodes. We also performed theoretical calculations to verify the selective manipulation through the floating AC-DEP force. A sufficiently high gradient of the square of the electric field (∇|E|2, ~1019 V2 m-3) was accomplished and

  7. Semiautomated isolation and molecular characterisation of single or highly purified tumour cells from CellSearch enriched blood samples using dielectrophoretic cell sorting

    PubMed Central

    Peeters, D J E; De Laere, B; Van den Eynden, G G; Van Laere, S J; Rothé, F; Ignatiadis, M; Sieuwerts, A M; Lambrechts, D; Rutten, A; van Dam, P A; Pauwels, P; Peeters, M; Vermeulen, P B; Dirix, L Y

    2013-01-01

    Background: Molecular characterisation of single circulating tumour cells (CTCs) holds considerable promise for predictive biomarker assessment and to explore CTC heterogeneity. We evaluate a new method, the DEPArray system, that allows the dielectrophoretic manipulation and isolation of single and 100% purified groups of CTCs from pre-enriched blood samples and explore the feasibility of their molecular characterisation. Methods: Samples containing known numbers of two cell populations were used to assess cell loss during sample loading. Cultured breast cancer cells were isolated from spiked blood samples using CellSearch CTC and Profile kits. Single tumour cells and groups of up to 10 tumour cells were recovered with the DEPArray system and subjected to transcriptional and mutation analysis. Results: On average, 40% cell loss was observed when loading samples to the DEPArray system. Expected mutations in clinically relevant markers could be obtained for 60% of single recovered tumour cells and all groups of tumour cells. Reliable gene expression profiles were obtained from single cells and groups of up to 10 cells for 2 out of 3 spiked breast cancer cell lines. Conclusion: We describe a semiautomated workflow for the isolation of small groups of 1 to 10 tumour cells from whole blood samples and provide proof of principle for the feasibility of their comprehensive molecular characterisation. PMID:23470469

  8. On-chip concentration of bacteria using a 3D dielectrophoretic chip and subsequent laser-based DNA extraction in the same chip

    NASA Astrophysics Data System (ADS)

    Cho, Yoon-Kyoung; Kim, Tae-hyeong; Lee, Jeong-Gun

    2010-06-01

    We report the on-chip concentration of bacteria using a dielectrophoretic (DEP) chip with 3D electrodes and subsequent laser-based DNA extraction in the same chip. The DEP chip has a set of interdigitated Au post electrodes with 50 µm height to generate a network of non-uniform electric fields for the efficient trapping by DEP. The metal post array was fabricated by photolithography and subsequent Ni and Au electroplating. Three model bacteria samples (Escherichia coli, Staphylococcus epidermidis, Streptococcus mutans) were tested and over 80-fold concentrations were achieved within 2 min. Subsequently, on-chip DNA extraction from the concentrated bacteria in the 3D DEP chip was performed by laser irradiation using the laser-irradiated magnetic bead system (LIMBS) in the same chip. The extracted DNA was analyzed with silicon chip-based real-time polymerase chain reaction (PCR). The total process of on-chip bacteria concentration and the subsequent DNA extraction can be completed within 10 min including the manual operation time.

  9. Theoretical and experimental examination of particle-particle interaction effects on induced dipole moments and dielectrophoretic responses of multiple particle chains.

    PubMed

    Moncada-Hernandez, Hector; Nagler, Eliot; Minerick, Adrienne R

    2014-07-01

    Dielectrophoresis (DEP), an electrokinetic phenomenon based on particle polarizations in nonuniform electric fields, is increasingly employed for particle and cell characterizations and manipulations in microdevices. However, particle number densities are rarely varied and particle-particle interactions are largely overlooked, but both affect particle's effective polarizations by changing the local electric field, which directly impacts particle assembly into chains. This work examines theoretical and experimental particle-particle interactions and dielectrophoretic responses in nonuniform electric fields, then presents individual and chain velocities of spherical polystyrene microparticles and red blood cells (RBCs) under DEP forces in a modified quadruple electrode microdevice. Velocities are independently compared between 1, 2, 3, and 4 polystyrene beads and RBCs assembled into chains aligned with the electric field. Simulations compared induced dipole moments for particles experiencing the same (single point) and changing (multiple points) electric fields. Experiments and simulations are compared by plotting DEP velocities versus applied signal frequency from 1 kHz to 80 MHz. Simulations indicate differences in the DEP force exerted on each particle according to chain position. Simulations and experiments show excellent qualitative agreement; chains with more particles experienced a decrease in the DEP response for both polystyrene beads and RBCs. These results advance understanding of the extent that induced dipole polarizations with multiple particle chains affect observed behaviors in electrokinetic cellular diagnostic systems.

  10. Selective nanomanipulation of fluorescent polystyrene nano-beads and single quantum dots at gold nanostructures based on the AC-dielectrophoretic force.

    PubMed

    Kim, Jinsik; Hwang, Kyo Seon; Lee, Sangyoup; Park, Jung Ho; Shin, Hyun-Joon

    2015-12-21

    We introduced the selective manipulation of polystyrene (PS) nano-beads and single quantum dots (QDs) at a gold nanostructure by using the AC-dielectrophoretic (DEP) force. Manipulation in three degrees of freedom (end-facet, side, and position-selective manipulation) was accomplished in gold nanostructures between microelectrodes. A 10 μm gap between the microelectrodes, which has a 100 nm-wide nanowire and 200 nm-wide vortex nanostructures at the inside of the gap, was fabricated, and nanostructures were not connected with the electrodes. We also performed theoretical calculations to verify the selective manipulation through the floating AC-DEP force. A sufficiently high gradient of the square of the electric field (∇|E|(2), ∼10(19) V(2) m(-3)) was accomplished and controlled for achieving a strong attaching force of nanoparticles using the gap between microelectrodes and nanostructures as well as the rotation of structures. Fluorescent PS nano-beads and QDs were attached at the designed end facet, side, and position of nanostructures with high selectivity. A single QD attachment was also realized at gold nanostructures, and the attached QDs were verified as single using optical "blinking" measurements.

  11. Bovine red blood cell starvation age discrimination through a glutaraldehyde-amplified dielectrophoretic approach with buffer selection and membrane cross-linking.

    PubMed

    Gagnon, Zachary; Gordon, Jason; Sengupta, Shramik; Chang, Hsueh-Chia

    2008-06-01

    We report a novel buffer electric and dielectric relaxation time tuning technique, coupled with a glutaraldehyde (Glt.) cross-linking cell fixation reaction that allows for sensitive dielectrophoretic analysis and discrimination of bovine red blood cells of different starvation age. Guided by a single-shell oblate spheroid model, a zwitterion buffer composition is selected to ensure that two measurable crossover frequencies (cof's) near 500 kHz exist for dielectrophoresis (DEP) within a small range of each other. It is shown that the low cof is sensitive to changes in the cell membrane dielectric constant, in which cross-linking by Glt. reduces the dielectric constant of the cell membrane from 10.5 to 3.8, while the high cof is sensitive to cell cytoplasm conductivity changes. We speculate that this enhanced particle polarizability that results from the cross-linking reaction is because younger (reduced starvation time) cells possess more amino groups that the reaction can release to enhance the cell interior ionic strength. Such sensitive discrimination of cells with different age (surface protein density) by DEP is not possible without the zwitterion buffer and cleavage by Glt. treatment. It is then expected that rapid identification and sorting of healthy from diseased cells can be similarly sensitized.

  12. Fractional vector calculus and fractional Maxwell's equations

    SciTech Connect

    Tarasov, Vasily E.

    2008-11-15

    The theory of derivatives and integrals of non-integer order goes back to Leibniz, Liouville, Grunwald, Letnikov and Riemann. The history of fractional vector calculus (FVC) has only 10 years. The main approaches to formulate a FVC, which are used in the physics during the past few years, will be briefly described in this paper. We solve some problems of consistent formulations of FVC by using a fractional generalization of the Fundamental Theorem of Calculus. We define the differential and integral vector operations. The fractional Green's, Stokes' and Gauss's theorems are formulated. The proofs of these theorems are realized for simplest regions. A fractional generalization of exterior differential calculus of differential forms is discussed. Fractional nonlocal Maxwell's equations and the corresponding fractional wave equations are considered.

  13. Equivariant mean field flow

    NASA Astrophysics Data System (ADS)

    Castéras, Jean-baptiste

    2013-12-01

    We consider a gradient flow associated to the mean field equation on (M,g), a compact Riemannian surface without boundary. We prove that this flow exists for all time. Moreover, letting G be a group of isometry acting on (M,g), we obtain the convergence of the flow to a solution of the mean field equation under suitable hypothesis on the orbits of points of M under the action of G.

  14. Full field flow visualization and computer-aided velocity measurements in a bank of cylinders in a wind tunnel

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Canacci, V. A.; Russell, L. M.

    1992-01-01

    The full field flow tracking (FFFT) method that is presented in this paper uses a laser-generated, mechanically strobed planar sheet of light, a low luminosity TV camera coupled with a long distance microscope, and a computer-controlled video recorder to study nonintrusively and qualitatively the flow structures in a bank of cylinders that are placed in a wind tunnel. This setup simulates an upscale version of the geometry of internal cooling passageways characteristic of small air-cooled radial turbines. The qualitative images supplied by the FFFT system are processed by means of a computer-integrated image quantification (CIIQ) method into quantitative information, trajectories and velocities, that describe the flow upstream of and within the bank of cylinders. The tracking method is Lagrangian in concept, and permits identification and tracking of the same particle, thus facilitating construction of time dependent trajectories and the calculation of true velocities and accelerations. The error analysis evaluates the accuracy with which the seed particles follow the flow and the errors incurred during the quantitative processing of the raw data derived from the FFFT/CIIQ method.

  15. Initialized Fractional Calculus

    NASA Technical Reports Server (NTRS)

    Lorenzo, Carl F.; Hartley, Tom T.

    2000-01-01

    This paper demonstrates the need for a nonconstant initialization for the fractional calculus and establishes a basic definition set for the initialized fractional differintegral. This definition set allows the formalization of an initialized fractional calculus. Two basis calculi are considered; the Riemann-Liouville and the Grunwald fractional calculi. Two forms of initialization, terminal and side are developed.

  16. Tempered fractional calculus

    SciTech Connect

    Sabzikar, Farzad; Meerschaert, Mark M.; Chen, Jinghua

    2015-07-15

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered fractional difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  17. TEMPERED FRACTIONAL CALCULUS

    PubMed Central

    MEERSCHAERT, MARK M.; SABZIKAR, FARZAD; CHEN, JINGHUA

    2014-01-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series. PMID:26085690

  18. Fraction Sense: Foundational Understandings.

    PubMed

    Fennell, Francis Skip; Karp, Karen

    2016-08-09

    The intent of this commentary is to identify elements of fraction sense and note how the research studies provided in this special issue, in related but somewhat different ways, validate the importance of such understandings. Proficiency with fractions serves as a prerequisite for student success in higher level mathematics, as well as serving as a gateway to many occupations and varied contexts beyond the mathematics classroom. Fraction sense is developed through instructional opportunities involving fraction equivalence and magnitude, comparing and ordering fractions, using fraction benchmarks, and computational estimation. Such foundations are then extended to operations involving fractions and decimals and applications involving proportional reasoning. These components of fraction sense are all addressed in the studies provided in this issue, with particular consideration devoted to the significant importance of the use of the number line as a central representational tool for conceptually understanding fraction magnitude. © Hammill Institute on Disabilities 2016.

  19. FRACTIONAL INTEGRATION TOOLBOX.

    PubMed

    Marinov, Toma M; Ramirez, Nelson; Santamaria, Fidel

    2013-09-01

    The problems formulated in the fractional calculus framework often require numerical fractional integration/differentiation of large data sets. Several existing fractional control toolboxes are capable of performing fractional calculus operations, however, none of them can efficiently perform numerical integration on multiple large data sequences. We developed a Fractional Integration Toolbox (FIT), which efficiently performs fractional numerical integration/differentiation of the Riemann-Liouville type on large data sequences. The toolbox allows parallelization and is designed to be deployed on both CPU and GPU platforms.

  20. Meaning of Fractions

    NASA Astrophysics Data System (ADS)

    Dewi, D. A. K.; Suryadi, D.; Suratno, T.; Mulyana, E.; Kurniawan, H.

    2017-02-01

    Introducing fractions is identical to divide an object. Suppose we divide the apple into two parts. One divided into two parts, the question arises whether one part can be called a half or not. Based on this activity, how can students give meaning to fractions. This study aims at designing a different fractions lesson by applying Didactical Design Research. In doing so, we undertook several research phases: 1) thinking what is fractions and why students should learn this concept; 2) designing didactical situation based on identified learning obstacles; and 3) reflecting retrospectively on the lesson design and its implementation as to redesign the fractions lesson. Our analysis revealed that most students held epistemological obstacles in giving meaning of fractions because they only know fractions as numbers that have numerator and denominator. By positioning ourselves as students, we discuss the ideal design to help students in constructing the meaning of fractions.

  1. DIY Fraction Pack.

    ERIC Educational Resources Information Center

    Graham, Alan; Graham, Louise

    2003-01-01

    Describes a very successful attempt to teach fractions to year 5 pupils based on pupils making their own fraction pack. Children decided for themselves how to make the fractional slices used in the activity using colored cardboard sheets and templates of a paper circle consisting of 24 equal slices. (Author/NB)

  2. Unfolding Fraction Multiplication

    ERIC Educational Resources Information Center

    Wyberg, Terry; Whitney, Stephanie R.; Cramer, Kathleen A.; Monson, Debra S.; Leavitt, Seth

    2011-01-01

    Students often have difficulty understanding fractions, in general, and understanding how to multiply fractions, in particular. To move past this potential problem area, students need to develop a deeper understanding of multiplication and connect the ideas to fractions. In this article, the authors share their insights into teaching fraction…

  3. DIY Fraction Pack.

    ERIC Educational Resources Information Center

    Graham, Alan; Graham, Louise

    2003-01-01

    Describes a very successful attempt to teach fractions to year 5 pupils based on pupils making their own fraction pack. Children decided for themselves how to make the fractional slices used in the activity using colored cardboard sheets and templates of a paper circle consisting of 24 equal slices. (Author/NB)

  4. Pitch fractionation. Technical report

    SciTech Connect

    Weinberg, V.L.; White, J.L.

    1981-12-15

    Petroleum pitch (Ashland A240) has been subjected to thermal treatment and solvent fractionation to produce refined pitches to be evaluated as impregnants for carbon-carbon composites. The solvent fractions were obtained by sequential Soxhlet extraction with solvents such as hexane, cyclohexane, toluene, and pyridine. The most severe thermal treatment produced a mesophase pitch (approximately 50% mesophase); an appreciable portion of the mesophase was soluble in strong solvents. There were substantial differences in chemical composition and in pyrolysis behavior of the fractions. As the depth of fraction increased, the pyrolysis yield and bloating increased, and the microstructure of the coke became finer until glassy microconstituents were formed in the deepest fractions.

  5. Fractionation and composition of colloidal and suspended particulate materials in rivers.

    PubMed

    Ran, Y; Fu, J M; Sheng, G Y; Beckett, R; Hart, B T

    2000-07-01

    The association of pollutants (nutrients, heavy metals and organic compounds) with colloidal and suspended particle matter (SPM) plays a dominant role in determining their transport, fate, biogeochemistry, bioavailability and toxicity in natural waters. A scheme for the fractionation and composition of colloidal and SPM from river waters has been tested. All four separation methods, i.e. sieving, continuous flow centrifugation, tangential flow filtration, sedimentation field-flow fractionation, were for the first time used to separate five size particulate fractions from river. Significant (gram) amounts of colloidal material (<1 microm) in three size ranges, nominally 1-0.2, 0.2-0.006 and 0.006-0.003 microm were obtained. The separation scheme was able to process large samples (100 l), within reasonable times (1 day) and the apparatus was portable. The aquatic colloid size was also characterized with high resolution by using sedimentation field-flow fractionation technique. The mass-based particle size distribution for the water sample showed a broad size distribution between 0.05 and 0.4 microm with the maximum around 0.14 microm. There was a systematic increase in the content of organic carbon (estimated by loss on ignition), Mg, Ca, Na, Cu and Zn with decreasing particle size, highlighting the importance of the colloidal (<1 microm) fraction. It was concluded that the colloidal Cu and Zn concentrations in rivers might be much higher than those reported before.

  6. Dividing Fractions: A Pedagogical Technique

    ERIC Educational Resources Information Center

    Lewis, Robert

    2016-01-01

    When dividing one fraction by a second fraction, invert, that is, flip the second fraction, then multiply it by the first fraction. To multiply fractions, simply multiply across the denominators, and multiply across the numerators to get the resultant fraction. So by inverting the division of fractions it is turned into an easy multiplication of…

  7. Dividing Fractions: A Pedagogical Technique

    ERIC Educational Resources Information Center

    Lewis, Robert

    2016-01-01

    When dividing one fraction by a second fraction, invert, that is, flip the second fraction, then multiply it by the first fraction. To multiply fractions, simply multiply across the denominators, and multiply across the numerators to get the resultant fraction. So by inverting the division of fractions it is turned into an easy multiplication of…

  8. FRACTIONAL PEARSON DIFFUSIONS.

    PubMed

    Leonenko, Nikolai N; Meerschaert, Mark M; Sikorskii, Alla

    2013-07-15

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change.

  9. FRACTIONAL PEARSON DIFFUSIONS

    PubMed Central

    Leonenko, Nikolai N.; Meerschaert, Mark M.

    2013-01-01

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change. PMID:23626377

  10. An Appetite for Fractions

    ERIC Educational Resources Information Center

    Wilkerson, Trena L.; Bryan, Tommy; Curry, Jane

    2012-01-01

    This article describes how using candy bars as models gives sixth-grade students a taste for learning to represent fractions whose denominators are factors of twelve. Using paper models of the candy bars, students explored and compared fractions. They noticed fewer different representations for one-third than for one-half. The authors conclude…

  11. Paper Folding Fractions

    ERIC Educational Resources Information Center

    Pagni, David

    2007-01-01

    In this article, the author presents a paper folding activity that can be used for teaching fractions. This activity can be used to describe areas of folded polygons in terms of a standard unit of measure. A paper folding fractions worksheet and its corresponding solutions are also presented in this article. (Contains 2 figures.)

  12. The Future of Fractions

    ERIC Educational Resources Information Center

    Usiskin, Zalman P.

    2007-01-01

    In the 1970s, the movement to the metric system (which has still not completely occurred in the United States) and the advent of hand-held calculators led some to speculate that decimal representation of numbers would render fractions obsolete. This provocative proposition stimulated Zalman Usiskin to write "The Future of Fractions" in 1979. He…

  13. On fractional programming

    SciTech Connect

    Bajona-Xandri, C.; Martinez-Legaz, J.E.

    1994-12-31

    This paper studies the minimax fractional programming problem, assuming quasiconvexity of the objective function, under the lower subdifferentiability viewpoint. Necessary and sufficient optimality conditions and dual properties are found. We present applications of this theory to find the Pareto efficient solutions of a multiobjective fractional problem and to solve several economic models.

  14. An Appetite for Fractions

    ERIC Educational Resources Information Center

    Wilkerson, Trena L.; Bryan, Tommy; Curry, Jane

    2012-01-01

    This article describes how using candy bars as models gives sixth-grade students a taste for learning to represent fractions whose denominators are factors of twelve. Using paper models of the candy bars, students explored and compared fractions. They noticed fewer different representations for one-third than for one-half. The authors conclude…

  15. Can Kindergartners Do Fractions?

    ERIC Educational Resources Information Center

    Cwikla, Julie

    2014-01-01

    Mathematics professor Julie Cwikla decided that she needed to investigate young children's understandings and see what precurricular partitioning notions young minds bring to the fraction table. Cwikla realized that only a handful of studies have examined how preschool-age and early elementary school-age students solve fraction problems (Empson…

  16. (Carbon isotope fractionation inplants)

    SciTech Connect

    O'Leary, M.H.

    1990-01-01

    The objectives of this research are: To develop a theoretical and experimental framework for understanding isotope fractionations in plants; and to develop methods for using this isotope fractionation for understanding the dynamics of CO{sub 2} fixation in plants. Progress is described.

  17. Can Kindergartners Do Fractions?

    ERIC Educational Resources Information Center

    Cwikla, Julie

    2014-01-01

    Mathematics professor Julie Cwikla decided that she needed to investigate young children's understandings and see what precurricular partitioning notions young minds bring to the fraction table. Cwikla realized that only a handful of studies have examined how preschool-age and early elementary school-age students solve fraction problems (Empson…

  18. Fractional dissipative standard map.

    PubMed

    Tarasov, Vasily E; Edelman, M

    2010-06-01

    Using kicked differential equations of motion with derivatives of noninteger orders, we obtain generalizations of the dissipative standard map. The main property of these generalized maps, which are called fractional maps, is long-term memory. The memory effect in the fractional maps means that their present state of evolution depends on all past states with special forms of weights. Already a small deviation of the order of derivative from the integer value corresponding to the regular dissipative standard map (small memory effects) leads to the qualitatively new behavior of the corresponding attractors. The fractional dissipative standard maps are used to demonstrate a new type of fractional attractors in the wide range of the fractional orders of derivatives.

  19. Fractionation and characterization of nano- and microparticles in liquid media.

    PubMed

    Fedotov, Petr S; Vanifatova, Nataliya G; Shkinev, Valery M; Spivakov, Boris Ya

    2011-06-01

    Submicron and micron particles present in liquid environmental, biological, and technological samples differ in their dimensions, shape, mass, chemical composition, and charge. Their properties cannot be reliably studied unless the particles are fractionated. Synthetic particles applied as components of analytical systems may also need preliminary fractionation and investigation. The review is focused on the methods for fractionation and characterization of nanoparticles and microparticles in liquid media, the most representative examples of their application, and the trends in developing novel approaches to the separation and investigation of particles. Among the separation techniques, the main attention is devoted to membrane filtration, field-flow fractionation, chromatographic, and capillary electrokinetic methods. Microfluidic systems employing the above-mentioned and other separation principles and providing a basis for the fabrication of lab-on-chip devices are also examined. Laser light scattering methods and other physical techniques for the characterization of particles are considered. Special attention is given to "hyphenated" techniques which enable the separation and characterization of particles to be performed in online modes.

  20. Microwave Dielectrophoretic Levitation In Microgravity

    NASA Technical Reports Server (NTRS)

    Watkins, John L.; Jackson, Henry W.; Barmatz, Martin B.

    1993-01-01

    Two reports propose use of dielectrophoresis in microwave resonant cavities to levitate samples of materials for containerless processing in microgravity in vacuum or in any suitable atmosphere. Also describe experiments undertaken to verify feasibility of proposal.

  1. Fractional calculus in bioengineering.

    PubMed

    Magin, Richard L

    2004-01-01

    Fractional calculus (integral and differential operations of noninteger order) is not often used to model biological systems. Although the basic mathematical ideas were developed long ago by the mathematicians Leibniz (1695), Liouville (1834), Riemann (1892), and others and brought to the attention of the engineering world by Oliver Heaviside in the 1890s, it was not until 1974 that the first book on the topic was published by Oldham and Spanier. Recent monographs and symposia proceedings have highlighted the application of fractional calculus in physics, continuum mechanics, signal processing, and electromagnetics, but with few examples of applications in bioengineering. This is surprising because the methods of fractional calculus, when defined as a Laplace or Fourier convolution product, are suitable for solving many problems in biomedical research. For example, early studies by Cole (1933) and Hodgkin (1946) of the electrical properties of nerve cell membranes and the propagation of electrical signals are well characterized by differential equations of fractional order. The solution involves a generalization of the exponential function to the Mittag-Leffler function, which provides a better fit to the observed cell membrane data. A parallel application of fractional derivatives to viscoelastic materials establishes, in a natural way, hereditary integrals and the power law (Nutting/Scott Blair) stress-strain relationship for modeling biomaterials. In this review, I will introduce the idea of fractional operations by following the original approach of Heaviside, demonstrate the basic operations of fractional calculus on well-behaved functions (step, ramp, pulse, sinusoid) of engineering interest, and give specific examples from electrochemistry, physics, bioengineering, and biophysics. The fractional derivative accurately describes natural phenomena that occur in such common engineering problems as heat transfer, electrode/electrolyte behavior, and sub

  2. Fractionation: past, present, future.

    PubMed

    Saedi, Nazanin; Jalian, H Ray; Petelin, Anthony; Zachary, Christopher

    2012-06-01

    The development of fractional photothermolysis is a milestone in the history of laser technology and cutaneous resurfacing. Based on the concept that skin is treated in a fractional manner, where narrow cylinders of tissue are thermally heated and normal adjacent skin is left unaffected, the fractional devices have shown effectiveness in treating a variety of conditions. Since its development, we are becoming more adept at using optimal parameters to induce near carbon dioxide laser benefits with a much more comfortable postoperative period and fewer complications. The future remains bright for fractionated laser devices and with new devices and wavelengths, the applications of this technology continue to grow. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Fractional market dynamics

    NASA Astrophysics Data System (ADS)

    Laskin, Nick

    2000-12-01

    A new extension of a fractality concept in financial mathematics has been developed. We have introduced a new fractional Langevin-type stochastic differential equation that differs from the standard Langevin equation: (i) by replacing the first-order derivative with respect to time by the fractional derivative of order μ; and (ii) by replacing “white noise” Gaussian stochastic force by the generalized “shot noise”, each pulse of which has a random amplitude with the α-stable Lévy distribution. As an application of the developed fractional non-Gaussian dynamical approach the expression for the probability distribution function (pdf) of the returns has been established. It is shown that the obtained fractional pdf fits well the central part and the tails of the empirical distribution of S&P 500 returns.

  4. Catalytic reforming of naphtha fractions

    SciTech Connect

    Bishop, K.C.; Vorhis, F.H.

    1980-09-16

    Production of motor gasoline and a btx-enriched reformate by fractionating a naphtha feedstock into a mid-boiling btxprecursor fraction, a relatively high-boiling fraction and a relatively low-boiling fraction; catalytically reforming the btxprecursor fraction in a first reforming zone; combining the relatively high-boiling and low-boiling fractions and catalytically reforming the combined fractions in a second reforming zone.

  5. Symmetric continued fractions

    SciTech Connect

    Panprasitwech, Oranit; Laohakosol, Vichian; Chaichana, Tuangrat

    2010-11-11

    Explicit formulae for continued fractions with symmetric patterns in their partial quotients are constructed in the field of formal power series. Similar to the work of Cohn in 1996, which generalized the so-called folding lemma to {kappa}-fold symmetry, the notion of {kappa}-duplicating symmetric continued fractions is investigated using a modification of the 1995 technique due to Clemens, Merrill and Roeder.

  6. Thermodynamics in Fractional Calculus

    NASA Astrophysics Data System (ADS)

    Meilanov, R. P.; Magomedov, R. A.

    2014-11-01

    A generalization of thermodynamics in the formalism of fractional-order derivatives is given. Results of the traditional thermodynamics of Carnot, Clausius, and Helmholtz are obtained in the particular case where the exponent of a fractional-order derivative is equal to unity. A one-parametric "fractal" equation of state is obtained with account of the second virial coefficient. The application of the resulting equation of state in the case of the gas argon is considered.

  7. Intracellular Cadmium Isotope Fractionation

    NASA Astrophysics Data System (ADS)

    Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

    2011-12-01

    Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

  8. Chromatographic methods of fractionation.

    PubMed

    Friesen, A D

    1987-01-01

    Chromatography's functional versatility, separation efficiency, gentle non-denaturing separating process and ease of automation and scale-up make it attractive for industrial scale protein purification. The Winnipeg Rh Institute's new Plasma Fractionation facility is an example of the use of chromatography for the large scale purification of plasma protein fractions. The fractionation facility has a capacity to process 800 litres of plasma per batch into blood clotting factor VIII and IX, albumin and intravenous immune serum globulin (i.v. ISG). Albumin and i.v. ISG are purified using ion exchange columns of DEAE-Sepharose (230 litre size), DEAE-Biogel (150 litre size) and CM-Sepharose (150 litre size). The chromatographic process is automated using a Modicon 584 Programmable Logic Controller to regulate valves, pumps and sensors which control plasma flow during fractionation. The stainless steel tanks and piping are automatically cleaned-in-place. The high degree of automation and cleaning provides efficient operation and sanitary processing. Chromatographic methods (DEAE-Sepharose and metal chelation) are also being used at the pilot scale to purify the human blood products superoxide dismutase and hemoglobin from outdated red blood cells. Characterization of the protein fractions produced by chromatography has shown them to be of equal or higher quality than fractions produced by other techniques.

  9. Fractional laser skin resurfacing.

    PubMed

    Alexiades-Armenakas, Macrene R; Dover, Jeffrey S; Arndt, Kenneth A

    2012-11-01

    Laser skin resurfacing (LSR) has evolved over the past 2 decades from traditional ablative to fractional nonablative and fractional ablative resurfacing. Traditional ablative LSR was highly effective in reducing rhytides, photoaging, and acne scarring but was associated with significant side effects and complications. In contrast, nonablative LSR was very safe but failed to deliver consistent clinical improvement. Fractional LSR has achieved the middle ground; it combined the efficacy of traditional LSR with the safety of nonablative modalities. The first fractional laser was a nonablative erbium-doped yttrium aluminum garnet (Er:YAG) laser that produced microscopic columns of thermal injury in the epidermis and upper dermis. Heralding an entirely new concept of laser energy delivery, it delivered the laser beam in microarrays. It resulted in microscopic columns of treated tissue and intervening areas of untreated skin, which yielded rapid reepithelialization. Fractional delivery was quickly applied to ablative wavelengths such as carbon dioxide, Er:YAG, and yttrium scandium gallium garnet (2,790 nm), providing more significant clinical outcomes. Adjustable laser parameters, including power, pitch, dwell time, and spot density, allowed for precise determination of percent surface area, affected penetration depth, and clinical recovery time and efficacy. Fractional LSR has been a significant advance to the laser field, striking the balance between safety and efficacy.

  10. Breakdown of doublet recirculation and direct line drives by far-field flow in reservoirs: implications for geothermal and hydrocarbon well placement

    NASA Astrophysics Data System (ADS)

    Weijermars, R.; van Harmelen, A.

    2016-07-01

    An important real world application of doublet flow occurs in well design of both geothermal and hydrocarbon reservoirs. A guiding principle for fluid management of injection and extraction wells is that mass balance is commonly assumed between the injected and produced fluid. Because the doublets are considered closed loops, the injection fluid is assumed to eventually reach the producer well and all the produced fluid ideally comes from stream tubes connected to the injector of the well pair making up the doublet. We show that when an aquifer background flow occurs, doublets will rarely retain closed loops of fluid recirculation. When the far-field flow rate increases relative to the doublet's strength, the area occupied by the doublet will diminish and eventually vanishes. Alternatively, rather than using a single injector (source) and single producer (sink), a linear array of multiple injectors separated by some distance from a parallel array of producers can be used in geothermal energy projects as well as in waterflooding of hydrocarbon reservoirs. Fluid flow in such an arrangement of parallel source-sink arrays is shown to be macroscopically equivalent to that of a line doublet. Again, any far-field flow that is strong enough will breach through the line doublet, which then splits into two vortices. Apart from fundamental insight into elementary flow dynamics, our new results provide practical clues that may contribute to improve the planning and design of doublets and direct line drives commonly used for flow management of groundwater, geothermal and hydrocarbon reservoirs.

  11. Continuous separation of breast cancer cells from blood samples using multi-orifice flow fractionation (MOFF) and dielectrophoresis (DEP).

    PubMed

    Moon, Hui-Sung; Kwon, Kiho; Kim, Seung-Il; Han, Hyunju; Sohn, Joohyuk; Lee, Soohyeon; Jung, Hyo-Il

    2011-03-21

    Circulating tumor cells (CTCs) are highly correlated with the invasive behavior of cancer, so their isolations and quantifications are important for biomedical applications such as cancer prognosis and measuring the responses to drug treatments. In this paper, we present the development of a microfluidic device for the separation of CTCs from blood cells based on the physical properties of cells. For use as a CTC model, we successfully separated human breast cancer cells (MCF-7) from a spiked blood cell sample by combining multi-orifice flow fractionation (MOFF) and dielectrophoretic (DEP) cell separation technique. Hydrodynamic separation takes advantage of the massive and high-throughput filtration of blood cells as it can accommodate a very high flow rate. DEP separation plays a role in precise post-processing to enhance the efficiency of the separation. The serial combination of these two different sorting techniques enabled high-speed continuous flow-through separation without labeling. We observed up to a 162-fold increase in MCF-7 cells at a 126 µL min(-1) flow rate. Red and white blood cells were efficiently removed with separation efficiencies of 99.24% and 94.23% respectively. Therefore, we suggest that our system could be used for separation and detection of CTCs from blood cells for biomedical applications.

  12. Modern plasma fractionation.

    PubMed

    Burnouf, Thierry

    2007-04-01

    Protein products fractionated from human plasma are an essential class of therapeutics used, often as the only available option, in the prevention, management, and treatment of life-threatening conditions resulting from trauma, congenital deficiencies, immunologic disorders, or infections. Modern plasma product production technology remains largely based on the ethanol fractionation process, but much has evolved in the last few years to improve product purity, to enhance the recovery of immunoglobulin G, and to isolate new plasma proteins, such as alpha1-protease inhibitor, von Willebrand factor, and protein C. Because of the human origin of the starting material and the pooling of 10,000 to 50,000 donations required for industrial processing, the major risk associated to plasma products is the transmission of blood-borne infectious agents. A complete set of measures--and, most particularly, the use of dedicated viral inactivation and removal treatments--has been implemented throughout the production chain of fractionated plasma products over the last 20 years to ensure optimal safety, in particular, and not exclusively, against HIV, hepatitis B virus, and hepatitis C virus. In this review, we summarize the practices of the modern plasma fractionation industry from the collection of the raw plasma material to the industrial manufacture of fractionated products. We describe the quality requirements of plasma for fractionation and the various treatments applied for the inactivation and removal of blood-borne infectious agents and provide examples of methods used for the purification of the various classes of plasma protein therapies. We also highlight aspects of the good manufacturing practices and the regulatory environment that govern the whole chain of production. In a regulated and professional environment, fractionated plasma products manufactured by modern processes are certainly among the lowest-risk therapeutic biological products in use today.

  13. Identifying Fractions on Number Lines.

    ERIC Educational Resources Information Center

    Bright, George W.; And Others

    1988-01-01

    This study investigated the ways students represented fractions on number lines and the effects of instruction on those representations. The instruction primarily concerned representing fractions and ordering fractions on number lines. (Author/PK)

  14. Fractionating nanosilver: importance for determining toxicity to aquatic test organisms.

    PubMed

    Kennedy, Alan J; Hull, Matthew S; Bednar, Anthony J; Goss, Jennifer D; Gunter, Jonas C; Bouldin, Jennifer L; Vikesland, Peter J; Steevens, Jeffery A

    2010-12-15

    This investigation applied novel techniques for characterizing and fractionating nanosilver particles and aggregates and relating these measurements to toxicological endpoints. The acute toxicity of eight nanosilver suspensions of varying primary particle sizes (10-80 nm) and coatings (citrate, polyvinylpyrrolidone, EDTA, proprietary) was assessed using three aquatic test organisms (Daphnia magna, Pimephales promelas, Pseudokirchneriella subcapitata). When 48-h lethal median concentrations (LC50) were expressed as total silver, both D. magna and P. promelas were significantly more sensitive to ionic silver (Ag(+)) as AgNO(3) (mean LC50 = 1.2 and 6.3 μg/L, respectively) relative to a wide range in LC50 values determined for the nanosilver suspensions (2 -126 μg/L). However, when LC50 values for nanosilver suspensions were expressed as fractionated nanosilver (Ag(+) and/or <4 nm particles), determined by ultracentrifugation of particles and confirmed field-flow-fractograms, the LC50 values (0.3-5.6 μg/L) were comparable to the values obtained for ionic Ag(+) as AgNO(3). These results suggest that dissolved Ag(+) plays a critical role in acute toxicity and underscores the importance of characterizing dissolved fractions in nanometal suspensions.

  15. Fractionator feed section

    SciTech Connect

    Sampath, V.R.; Bachmann, D.E.

    1993-07-27

    A fractionator feed section in a fractionator to which is fed a feed mixture comprising a vapor component and a liquid component and which fractionator comprises a tray above said feed section which passes liquid reflux to said feed section, said feed section comprising: (a) a downwardly extending, elongated first baffle; (b) a downwardly extending, elongated second baffle; (c) a seal pan below said first baffle and said second baffle, said seal pan comprising a seal pan mixture of liquids into which a portion of said first baffle and a portion of said second baffle extend to form a mixing zone; (d) a feed nozzle which introduces said liquid component and said vapor component downward into said mixing zone; and, (e) a trough which introduces said liquid reflux to said mixing zone, wherein said liquid component and said liquid reflux mix to form said seal pan mixture of liquids.

  16. Iterated fractional Tikhonov regularization

    NASA Astrophysics Data System (ADS)

    Bianchi, Davide; Buccini, Alessandro; Donatelli, Marco; Serra-Capizzano, Stefano

    2015-05-01

    Fractional Tikhonov regularization methods have been recently proposed to reduce the oversmoothing property of the Tikhonov regularization in standard form, in order to preserve the details of the approximated solution. Their regularization and convergence properties have been previously investigated showing that they are of optimal order. This paper provides saturation and converse results on their convergence rates. Using the same iterative refinement strategy of iterated Tikhonov regularization, new iterated fractional Tikhonov regularization methods are introduced. We show that these iterated methods are of optimal order and overcome the previous saturation results. Furthermore, nonstationary iterated fractional Tikhonov regularization methods are investigated, establishing their convergence rate under general conditions on the iteration parameters. Numerical results confirm the effectiveness of the proposed regularization iterations.

  17. Fractional generalization of Liouville equations.

    PubMed

    Tarasov, Vasily E

    2004-03-01

    In this paper fractional generalization of Liouville equation is considered. We derive fractional analog of normalization condition for distribution function. Fractional generalization of the Liouville equation for dissipative and Hamiltonian systems was derived from the fractional normalization condition. This condition is considered as a normalization condition for systems in fractional phase space. The interpretation of the fractional space is discussed. Copyright 2004 American Institute of Physics.

  18. Release Fraction Evaluation

    SciTech Connect

    Bamberger, Judith A.; Glissmeyer, John A.

    2004-01-01

    This document presents results of experiments conducted to measure release fractions during certain tank retrieval processes. The tests were performed in a 1/4 scale model of a waste storage tank. The retrieval processes simulated were: (1) Discharging liquid or slurry from the mouth of a vertically oriented two-in. Schedule 40 pipe. The discharging material was in free-fall from the mouth of the pipe near the top of the tank into a liquid or slurry pool at the bottom of the tank. (2) The jet from a 9/16-in.-diameter nozzle transferring liquid or slurry waste from one side of the tank to the other. The discharging liquid was aimed at the opposite side of the tank from the nozzle and either impacted the tank wall or fell into a liquid or slurry pool in the bottom of the tank. (3) A high pressure fan jet of liquid striking a steel plate or simulated waste from a stand-off distance of a few inches. For each process, a water-soluble fluorescent dye was added to the liquid fraction as a tracer. Kaolin clay was used to represent the solids. The tank was covered and there was no forced ventilation in the tank during the tests. Six air samples were collected during each test. The air samples were collected at fixed positions in the tank. The air sample filters were dried and weighed to determine the solids collection. The fluorescent dye was then leached from each filter and quantified with a fluorometer to determine the collection of liquid. Samples of the slurry and liquid simulants were also collected to determine the quantities of simulant used in each test. To calculate the release fraction, the quantity collected on each air sample was adjusted for the fraction of the tank volume sampled and divided by the quantity of material exposed in the simulation. The method was not as sensitive for the solids content as it was for the liquid content, but in those instances where a solids release fraction was determined, it was in relatively good agreement with that of the

  19. FRACTIONAL CRYSTALLIZATION FEED ENVELOPE

    SciTech Connect

    HERTING DL

    2008-03-19

    Laboratory work was completed on a set of evaporation tests designed to establish a feed envelope for the fractional crystallization process. The feed envelope defines chemical concentration limits within which the process can be operated successfully. All 38 runs in the half-factorial design matrix were completed successfully, based on the qualitative definition of success. There is no feed composition likely to be derived from saltcake dissolution that would cause the fractional crystallization process to not meet acceptable performance requirements. However, some compositions clearly would provide more successful operation than other compositions.

  20. Videodisc Instruction in Fractions.

    ERIC Educational Resources Information Center

    Carnine, Douglas; And Others

    1987-01-01

    How laser videodisc technology can be used to improve mathematics instruction is described, with note of the development of a videodisc curriculum on mastering fractions. Relevant research is reviewed, as well as how teachers can use the technology. The instructional design is described, and field-testing and revision reported. (MNS)

  1. Sweet Work with Fractions

    ERIC Educational Resources Information Center

    Vinogradova, Natalya; Blaine, Larry

    2013-01-01

    Almost everyone loves chocolate. However, the same cannot be said about fractions, which are loved by markedly fewer. Middle school students tend to view them with wary respect, but little affection. The authors attempt to sweeten the subject by describing a type of game involving division of chocolate bars. The activity they describe provides a…

  2. Fractional charge search

    SciTech Connect

    Innes, W.; Klein, S.; Perl, M.; Price, J.C.

    1982-06-01

    A device to search for fractional charge in matter is described. The sample is coupled to a low-noise amplifier by a periodically varying capacitor and the resulting signal is synchronously detected. The varying capacitor is constructed as a rapidly spinning wheel. Samples of any material in volumes of up to 0.05 ml may be searched in less than an hour.

  3. Fraction collector for electrophoresis

    NASA Technical Reports Server (NTRS)

    Bier, M.

    1977-01-01

    Rotating-tube electrophoresis apparatus employs rotating jet of eluting buffer to reduce effects of convection during separation. Designed for separation of microorganisms and biological species, system combines gravity/gradient compensating of lumen with buffer flush at fraction outlet to increase separation efficiency.

  4. Fractions through Fruit Salad.

    ERIC Educational Resources Information Center

    Lincoln, Lisa

    1987-01-01

    The mathematics concept of fractions was taught to a group of learning disabled, dyslexic, and multiply handicapped students (15-20 years old) by preparing a fruit salad. Enthusiastic student participation and enhanced knowledge illustrated the effectiveness of employing several sensory modes in learning activities. (CB)

  5. Momentum fractionation on superstrata

    SciTech Connect

    Bena, Iosif; Martinec, Emil; Turton, David; Warner, Nicholas P.

    2016-05-11

    Superstrata are bound states in string theory that carry D1, D5, and momentum charges, and whose supergravity descriptions are parameterized by arbitrary functions of (at least) two variables. In the D1-D5 CFT, typical three-charge states reside in highdegree twisted sectors, and their momentum charge is carried by modes that individually have fractional momentum. Understanding this momentum fractionation holographically is crucial for understanding typical black-hole microstates in this system. We use solution-generating techniques to add momentum to a multi-wound supertube and thereby construct the first examples of asymptotically-flat superstrata. The resulting supergravity solutions are horizonless and smooth up to well-understood orbifold singularities. Upon taking the AdS3 decoupling limit, our solutions are dual to CFT states with momentum fractionation. We give a precise proposal for these dual CFT states. Lastly, our construction establishes the very nontrivial fact that large classes of CFT states with momentum fractionation can be realized in the bulk as smooth horizonless supergravity solutions.

  6. Sweet Work with Fractions

    ERIC Educational Resources Information Center

    Vinogradova, Natalya; Blaine, Larry

    2013-01-01

    Almost everyone loves chocolate. However, the same cannot be said about fractions, which are loved by markedly fewer. Middle school students tend to view them with wary respect, but little affection. The authors attempt to sweeten the subject by describing a type of game involving division of chocolate bars. The activity they describe provides a…

  7. Momentum fractionation on superstrata

    DOE PAGES

    Bena, Iosif; Martinec, Emil; Turton, David; ...

    2016-05-11

    Superstrata are bound states in string theory that carry D1, D5, and momentum charges, and whose supergravity descriptions are parameterized by arbitrary functions of (at least) two variables. In the D1-D5 CFT, typical three-charge states reside in highdegree twisted sectors, and their momentum charge is carried by modes that individually have fractional momentum. Understanding this momentum fractionation holographically is crucial for understanding typical black-hole microstates in this system. We use solution-generating techniques to add momentum to a multi-wound supertube and thereby construct the first examples of asymptotically-flat superstrata. The resulting supergravity solutions are horizonless and smooth up to well-understood orbifoldmore » singularities. Upon taking the AdS3 decoupling limit, our solutions are dual to CFT states with momentum fractionation. We give a precise proposal for these dual CFT states. Lastly, our construction establishes the very nontrivial fact that large classes of CFT states with momentum fractionation can be realized in the bulk as smooth horizonless supergravity solutions.« less

  8. Fractionation of human serum lipoproteins and simultaneous enzymatic determination of cholesterol and triglycerides.

    PubMed

    Qureshi, Rashid Nazir; Kok, Wim Th; Schoenmakers, Peter J

    2009-11-03

    A method based on Asymmetric Flow Field-Flow Fractionation (AF4) was developed to separate different types of lipoproteins from human serum. The emphasis in the method optimization was on the possibilities to characterize the largest lipoprotein fractions (LDL and VLDL), which is usually not possible with the size-exclusion chromatography methods applied in routine analysis. Different channel geometries and flow programs were tested and compared. The use of a short fractionation channel was shown to give less sample dilution at the same fractionation power compared to a conventional, long channel. Different size selectivities were obtained with an exponential decay and a linear cross flow program. The ratio of the UV absorption signal to the light scattering signal was used to validate the relation between retention time and size of the fractionated particles. An experimental setup was developed for the simultaneous determination of the cholesterol and triglycerides distribution over the lipoprotein fractions, based on enzymatic reactions followed by UV detection at 500 nm. Coiled and knitted PTFE tubing reactors were compared. An improved peak sharpness and sensitivity were observed with the knitted tubing reactor. After optimization of the experimental conditions a satisfactory linearity and precision (2-3% rsd for cholesterol and 5-6% rsd for triglycerides) were obtained. Finally, serum samples, a pooled sample from healthy volunteers and samples of sepsis patients, were analyzed with the method developed. Lipoprotein fractionation and cholesterol and triglyceride distributions could be correlated with the clinical background of the samples.

  9. Goal Sketches in Fraction Learning

    ERIC Educational Resources Information Center

    Sophian, Catherine; Madrid, Samara

    2003-01-01

    To examine how conceptual knowledge about fraction magnitudes changes as students' learning progresses, 5th and 7th-grade students were asked to solve fraction magnitude problems that entailed finding a fraction between two given fractions and then to evaluate solutions for similar problems that were modeled for them. When the given fractions…

  10. Creating, Naming, and Justifying Fractions

    ERIC Educational Resources Information Center

    Siebert, Daniel; Gaskin, Nicole

    2006-01-01

    For students to develop meaningful conceptions of fractions and fraction operations, they need to think of fractions in terms other than as just whole-number combinations. In this article, we suggest two powerful images for thinking about fractions that move beyond whole-number reasoning. (Contains 5 figures.)

  11. Arbitrage with fractional Gaussian processes

    NASA Astrophysics Data System (ADS)

    Zhang, Xili; Xiao, Weilin

    2017-04-01

    While the arbitrage opportunity in the Black-Scholes model driven by fractional Brownian motion has a long history, the arbitrage strategy in the Black-Scholes model driven by general fractional Gaussian processes is in its infancy. The development of stochastic calculus with respect to fractional Gaussian processes allowed us to study such models. In this paper, following the idea of Shiryaev (1998), an arbitrage strategy is constructed for the Black-Scholes model driven by fractional Gaussian processes, when the stochastic integral is interpreted in the Riemann-Stieltjes sense. Arbitrage opportunities in some fractional Gaussian processes, including fractional Brownian motion, sub-fractional Brownian motion, bi-fractional Brownian motion, weighted-fractional Brownian motion and tempered fractional Brownian motion, are also investigated.

  12. Floquet Fractional Chern Insulators

    NASA Astrophysics Data System (ADS)

    Grushin, Adolfo G.; Gómez-León, Álvaro; Neupert, Titus

    2014-04-01

    We show theoretically that periodically driven systems with short range Hubbard interactions offer a feasible platform to experimentally realize fractional Chern insulator states. We exemplify the procedure for both the driven honeycomb and the square lattice, where we derive the effective steady state band structure of the driven system by using the Floquet theory and subsequently study the interacting system with exact numerical diagonalization. The fractional Chern insulator state equivalent to the 1/3 Laughlin state appears at 7/12 total filling (1/6 filling of the upper band). The state also features spontaneous ferromagnetism and is thus an example of the spontaneous breaking of a continuous symmetry along with a topological phase transition. We discuss light-driven graphene and shaken optical lattices as possible experimental systems that can realize such a state.

  13. Testing fractional action cosmology

    NASA Astrophysics Data System (ADS)

    Shchigolev, V. K.

    2016-08-01

    The present work deals with a combined test of the so-called Fractional Action Cosmology (FAC) on the example of a specific model obtained by the author earlier. In this model, the effective cosmological term is proportional to the Hubble parameter squared through the so-called kinematic induction. The reason of studying this cosmological model could be explained by its ability to describe two periods of accelerated expansion, that is in agreement with the recent observations and the cosmological inflation paradigm. First of all, we put our model through the theoretical tests, which gives a general conception of the influence of the model parameters on its behavior. Then, we obtain some restrictions on the principal parameters of the model, including the fractional index, by means of the observational data. Finally, the cosmography parameters and the observational data compared to the theoretical predictions are presented both analytically and graphically.

  14. Fractional lattice charge transport

    PubMed Central

    Flach, Sergej; Khomeriki, Ramaz

    2017-01-01

    We consider the dynamics of noninteracting quantum particles on a square lattice in the presence of a magnetic flux α and a dc electric field E oriented along the lattice diagonal. In general, the adiabatic dynamics will be characterized by Bloch oscillations in the electrical field direction and dispersive ballistic transport in the perpendicular direction. For rational values of α and a corresponding discrete set of values of E(α) vanishing gaps in the spectrum induce a fractionalization of the charge in the perpendicular direction - while left movers are still performing dispersive ballistic transport, the complementary fraction of right movers is propagating in a dispersionless relativistic manner in the opposite direction. Generalizations and the possible probing of the effect with atomic Bose-Einstein condensates and photonic networks are discussed. Zak phase of respective band associated with gap closing regime has been computed and it is found converging to π/2 value. PMID:28102302

  15. New Dry Fractionation Methods

    NASA Technical Reports Server (NTRS)

    McKay, David S.; Cooper, Bonnie L.

    2010-01-01

    This slide presentation describes new fractionation methods that are used to create dust that is respirable for testing the effects of inhalation of lunar dust in preparation for future manned lunar exploration. Because lunar dust is a very limited commodity, a method that does not result in loss of the material had to be developed. The dust separation system that is described incorporates some traditional methods, while preventing the dust from being contaminated or changed in reactivity properties while also limiting losses.

  16. Fractional Galilean symmetries

    NASA Astrophysics Data System (ADS)

    Hosseiny, Ali; Rouhani, Shahin

    2016-09-01

    We generalize the differential representation of the operators of the Galilean algebras to include fractional derivatives. As a result a whole new class of scale invariant Galilean algebras are obtained. The first member of this class has dynamical index z = 2 similar to the Schrödinger algebra. The second member of the class has dynamical index z = 3 / 2, which happens to be the dynamical index Kardar-Parisi-Zhang equation.

  17. Fractional statistics from gravitation

    SciTech Connect

    Cho, Y.M. ); Park, D.H. )

    1994-06-15

    We show that the solitons of the SO(3) nonlinear sigma model in 2+1 dimensions, when coupled to gravitation with the gravitational Chern-Simons interaction, become anyons in the absence of the Hopf term. In particular we calculate the fractional statistical factor of the gravitating anyons, and prove that the gravitational Chern-Simons term itself can be interpreted as the Hopf term of the topological current of [Pi][sub 2]([ital S][sup 2]).

  18. Model Fractional Chern Insulators

    NASA Astrophysics Data System (ADS)

    Behrmann, Jörg; Liu, Zhao; Bergholtz, Emil J.

    2016-05-01

    We devise local lattice models whose ground states are model fractional Chern insulators—Abelian and non-Abelian topologically ordered states characterized by exact ground state degeneracies at any finite size and infinite entanglement gaps. Most saliently, we construct exact parent Hamiltonians for two distinct families of bosonic lattice generalizations of the Zk parafermion quantum Hall states: (i) color-entangled fractional Chern insulators at band filling fractions ν =k /(C +1 ) and (ii) nematic states at ν =k /2 , where C is the Chern number of the lowest band. In spite of a fluctuating Berry curvature, our construction is partially frustration free: the ground states reside entirely within the lowest band and exactly minimize a local (k +1 ) body repulsion term by term. In addition to providing the first known models hosting intriguing states such as higher Chern number generalizations of the Fibonacci anyon quantum Hall states, the remarkable stability and finite-size properties make our models particularly well suited for the study of novel phenomena involving, e.g., twist defects and proximity induced superconductivity, as well as being a guide for designing experiments.

  19. Model Fractional Chern Insulators.

    PubMed

    Behrmann, Jörg; Liu, Zhao; Bergholtz, Emil J

    2016-05-27

    We devise local lattice models whose ground states are model fractional Chern insulators-Abelian and non-Abelian topologically ordered states characterized by exact ground state degeneracies at any finite size and infinite entanglement gaps. Most saliently, we construct exact parent Hamiltonians for two distinct families of bosonic lattice generalizations of the Z_{k} parafermion quantum Hall states: (i) color-entangled fractional Chern insulators at band filling fractions ν=k/(C+1) and (ii) nematic states at ν=k/2, where C is the Chern number of the lowest band. In spite of a fluctuating Berry curvature, our construction is partially frustration free: the ground states reside entirely within the lowest band and exactly minimize a local (k+1) body repulsion term by term. In addition to providing the first known models hosting intriguing states such as higher Chern number generalizations of the Fibonacci anyon quantum Hall states, the remarkable stability and finite-size properties make our models particularly well suited for the study of novel phenomena involving, e.g., twist defects and proximity induced superconductivity, as well as being a guide for designing experiments.

  20. [Ablative and fractional lasers].

    PubMed

    Beylot, C; Grognard, C; Michaud, T

    2009-10-01

    The use of pulsed or scanning Carbon Dioxide, and pulsed Erbium-YAG lasers allows the programmable and reproducible photocoagulation of thin layers of the epidermis and superficial dermis. Thermal damage depends on the type of laser and is greater with CO(2) lasers. The degree of neocollagenesis is proportional to the thermal damage and is better with CO(2) lasers. Their main indication is the correction of photoaged facial skin but they can also be used for corrective dermatology, e.g. for scars and genodermatosis. Results are highly satisfactory but the technique is invasive and the patient experiences a social hindrance of around two weeks. Fractionated techniques treat 25% of the defective skin area at each session in noncontiguous microzones; four sessions are therefore necessary to treat the entire cutaneous surface. The treatment is given under topical anesthesia and is much less invasive, particularly with nonablative fractional laser treatment in which photothermolysis does not penetrate below the epidermis and/or the effects are slight, with no or very little social isolation. However, the results are much less satisfactory than the results of ablative laser and there is no firming effect. Other zones than the face can be treated. With the fractional CO(2) and Erbium ablative lasers, which have multiplied over the past 2 years, the much wider impacts cause perforation of the epidermis and there is a zone of ablation by laser photovaporization, with a zone of thermal damage below. The results are better in correcting photoaging of the face, without, however, achieving the efficacy of ablative lasers, which remain the reference technique. However, the effects are not insignificant, requiring at least 5 days of social isolation.

  1. Fractional Langevin equation and Riemann-Liouville fractional derivative.

    PubMed

    Sau Fa, Kwok

    2007-10-01

    In this present work we consider a fractional Langevin equation with Riemann-Liouville fractional time derivative which modifies the classical Newtonian force, nonlocal dissipative force, and long-time correlation. We investigate the first two moments, variances and position and velocity correlation functions of this system. We also compare them with the results obtained from the same fractional Langevin equation which uses the Caputo fractional derivative.

  2. Preheating with fractional powers

    NASA Astrophysics Data System (ADS)

    Moghaddam, Hossein Bazrafshan; Brandenberger, Robert

    2016-11-01

    We consider preheating in models in which the potential for the inflaton is given by a fractional power, as is the case in axion monodromy inflation. We assume a standard coupling between the inflaton field and a scalar matter field. We find that in spite of the fact that the oscillation of the inflaton about the field value which minimizes the potential is anharmonic, there is nevertheless a parametric resonance instability, and we determine the Floquet exponent which describes this instability as a function of the parameters of the inflaton potential.

  3. Solvent Fractionation of Lignin

    SciTech Connect

    Chatterjee, Sabornie; Saito, Tomonori

    2014-01-01

    Lignin is a highly abundant source of renewable carbon that can be considered as a valuable sustainable source of biobased materials. The major issues for the commercial production of value added high performance lignin products are lignin s physical and chemical heterogenities. To overcome these problems, a variety of procedures have been developed to produce pure lignin suitable for high performace applications such as lignin-derived carbon materials. However, most of the isolation procedures affect lignin s properties and structure. In this chapter, a short review of the effect of solvent fractionation on lignin s properties and structure is presented.

  4. Fractional channel multichannel analyzer

    DOEpatents

    Brackenbush, Larry W.; Anderson, Gordon A.

    1994-01-01

    A multichannel analyzer incorporating the features of the present invention obtains the effect of fractional channels thus greatly reducing the number of actual channels necessary to record complex line spectra. This is accomplished by using an analog-to-digital converter in the asynscronous mode, i.e., the gate pulse from the pulse height-to-pulse width converter is not synchronized with the signal from a clock oscillator. This saves power and reduces the number of components required on the board to achieve the effect of radically expanding the number of channels without changing the circuit board.

  5. Fractional channel multichannel analyzer

    DOEpatents

    Brackenbush, L.W.; Anderson, G.A.

    1994-08-23

    A multichannel analyzer incorporating the features of the present invention obtains the effect of fractional channels thus greatly reducing the number of actual channels necessary to record complex line spectra. This is accomplished by using an analog-to-digital converter in the asynchronous mode, i.e., the gate pulse from the pulse height-to-pulse width converter is not synchronized with the signal from a clock oscillator. This saves power and reduces the number of components required on the board to achieve the effect of radically expanding the number of channels without changing the circuit board. 9 figs.

  6. Fractional Lindstedt series

    NASA Astrophysics Data System (ADS)

    Gallavotti, G.; Gentile, G.; Giuliani, A.

    2006-01-01

    The parametric equations of the surfaces on which highly resonant quasiperiodic motions develop (lower-dimensional tori) cannot be analytically continued, in general, in the perturbation parameter ɛ, i.e., they are not analytic functions of ɛ. However rather generally quasiperiodic motions whose frequencies satisfy only one rational relation ("resonances of order 1") admit formal perturbation expansions in terms of a fractional power of ɛ depending on the degeneration of the resonance. We find conditions for this to happen, and in such a case we prove that the formal expansion is convergent after suitable resummation.

  7. Characterization of Nanomaterials Using Field Flow Fractionation and Single Particle Inductively Coupled Plasma Mass Spectrometery (FFF-ICP-MS and SP-ICP-MS): Scientific Operating Procedure SOP-C

    DTIC Science & Technology

    2015-04-01

    8012 citrate-stabilized 30 nm gold (Au), Nanocomposix 30 nm silver, and NIST SRM 1898 Titanium Dioxide nanomaterial ( TiO2 ), among others. However...Diego), various sizes o NIST SRMs 8011, 8012, 8013 (50 mg/L Au, various sizes) o NIST SRM 1898 TiO2 • Polystyrene standard particles (20, 50, 100 nm...SRM 1898 TiO2 , as shown in Figure 5 below. Two suspensions were prepared according to ERDC/EL SR-15-1, and analyzed within 1 day of preparation

  8. CHARACTERIZATION OF SUB-MICRON AQUEOUS IRON(III) COLLOIDS FORMED IN THE PRESENCE OF PHOSPHATE BY SEDIMENTATION FIELD FLOW FRACTIONATION WITH MULTI-ANGLE LASER LIGHT SCATTERING DETECTION

    EPA Science Inventory

    Iron colloids play a major role in the water chemistry of natural watersheds and of engineered drinking water distribution systems. Phosphate is frequently added to distribution systems to control corrosion problems, so iron-phosphate colloids may form through reaction of iron in...

  9. CHARACTERIZATION OF SUB-MICRON AQUEOUS IRON(III) COLLOIDS FORMED IN THE PRESENCE OF PHOSPHATE BY SEDIMENTATION FIELD FLOW FRACTIONATION WITH MULTI-ANGLE LASER LIGHT SCATTERING DETECTION

    EPA Science Inventory

    Iron colloids play a major role in the water chemistry of natural watersheds and of engineered drinking water distribution systems. Phosphate is frequently added to distribution systems to control corrosion problems, so iron-phosphate colloids may form through reaction of iron in...

  10. Body Fractions: A Physical Approach to Fraction Learning

    ERIC Educational Resources Information Center

    Mills, Judith

    2011-01-01

    Many students experience great difficulty understanding the meaning of fractions. For many students who have spent their early mathematics lessons focusing on counting (whole) numbers, recognising that there are many numbers between those whole numbers called fractional numbers, is quite revolutionary. The foundation of understanding fractions is…

  11. Field Flows of Dark Energy

    SciTech Connect

    Cahn, Robert N.; de Putter, Roland; Linder, Eric V.

    2008-07-08

    Scalar field dark energy evolving from a long radiation- or matter-dominated epoch has characteristic dynamics. While slow-roll approximations are invalid, a well defined field expansion captures the key aspects of the dark energy evolution during much of the matter-dominated epoch. Since this behavior is determined, it is not faithfully represented if priors for dynamical quantities are chosen at random. We demonstrate these features for both thawing and freezing fields, and for some modified gravity models, and unify several special cases in the literature.

  12. Fractional Vorticity Equations

    NASA Astrophysics Data System (ADS)

    Schertzer, D.; Tchguirinskaia, I.; Lovejoy, S.; Tuck, A.

    2012-04-01

    As a result of a thorough discussion (Schertzer et al., Atmos. Chem. Phys., 12, 327-336, 2012 ) of the limitations of the quasi-geostrophic approximation and turbulence, fractional vorticity equations were obtained. This was done with the help of an anisotropic scaling analysis, instead of the classical scale analysis, as done to derive the quasi-geostrophic approximation. This breaks the rotational symmetry of the classical 3D vorticity equations and a priori yields a (2 + Hz)-dimensional turbulence (0 ≤ Hz ≤ 1). This corresponds to a first step in the derivation of a dynamical alternative to the quasi-geostrophic approximation and turbulence. The corresponding precise definition of fractional dimensional turbulence already demonstrates that the classical 2-D and 3-D turbulence are not the main options to understand atmospheric and oceanic dynamics. Although (2 + Hz)-dimensional turbulence (with 0 < Hz < 1) has more common features with 3-D turbulence than with 2-D turbulence, it has nevertheless very distinctive features: its scaling anisotropy is in agreement with the layered pancake structure, which is typical of rotating and stratified turbulence, but not of the classical 3-D turbulence. In this presentation, we further discuss the properties of this set of deterministic-like equations, especially how they can generate a statistical scaling anisotropy, as well as the relevance of the theoretical value Hz = 5/9.

  13. [Ablative and fractional lasers].

    PubMed

    Beylot, C

    2008-02-01

    The use of pulsed or scanning Carbon Dioxide, and pulsed Erbium-YAG lasers allows the programmable and reproducible photocoagulation of thin layers of the epidermis and superficial dermis. Thermal damage depends on the type of laser and is greater with CO(2) lasers. The degree of neocollagenesis is proportional to the thermal damage and is better with CO(2) lasers. Their main indication is the correction of photoaged facial skin but they can also be used for corrective dermatology, e.g. for scars and genodermatosis. Results are highly satisfactory but the technique is invasive and the patient experiences a social hindrance of around two weeks. The fractional techniques such as Fraxel are used to treat non-adjacent microzones without ablation of the epidermis. Around 25 p. 100 of the affected region is treated per session without ablation of the epidermis. Each fraction is only mini-invasive and is performed under local anesthesia. Social hindrance is minimal. Nonetheless, the results are inferior to those obtained with ablative lasers, especially regarding deep wrinkles. The treatment is costly and four sessions are usually required to treat the whole affected area. Others regions of the face may also be treated. Encouraging results have been obtained with mélasma.

  14. Ejection Fraction Heart Failure Measurement

    MedlinePlus

    ... Thromboembolism Aortic Aneurysm More Ejection Fraction Heart Failure Measurement Updated:Feb 15,2017 The ejection fraction (EF) is an important measurement in determining how well your heart is pumping ...

  15. Positive fractional linear electrical circuits

    NASA Astrophysics Data System (ADS)

    Kaczorek, Tadeusz

    2013-10-01

    The positive fractional linear systems and electrical circuits are addressed. New classes of fractional asymptotically stable and unstable electrical circuits are introduced. The Caputo and Riemann-Liouville definitions of fractional derivatives are used to analysis of the positive electrical circuits composed of resistors, capacitors, coils and voltage (current) sources. The positive fractional electrical and specially unstable different types electrical circuits are analyzed. Some open problems are formulated.

  16. Fractional Hopfield Neural Networks: Fractional Dynamic Associative Recurrent Neural Networks.

    PubMed

    Pu, Yi-Fei; Yi, Zhang; Zhou, Ji-Liu

    2017-10-01

    This paper mainly discusses a novel conceptual framework: fractional Hopfield neural networks (FHNN). As is commonly known, fractional calculus has been incorporated into artificial neural networks, mainly because of its long-term memory and nonlocality. Some researchers have made interesting attempts at fractional neural networks and gained competitive advantages over integer-order neural networks. Therefore, it is naturally makes one ponder how to generalize the first-order Hopfield neural networks to the fractional-order ones, and how to implement FHNN by means of fractional calculus. We propose to introduce a novel mathematical method: fractional calculus to implement FHNN. First, we implement fractor in the form of an analog circuit. Second, we implement FHNN by utilizing fractor and the fractional steepest descent approach, construct its Lyapunov function, and further analyze its attractors. Third, we perform experiments to analyze the stability and convergence of FHNN, and further discuss its applications to the defense against chip cloning attacks for anticounterfeiting. The main contribution of our work is to propose FHNN in the form of an analog circuit by utilizing a fractor and the fractional steepest descent approach, construct its Lyapunov function, prove its Lyapunov stability, analyze its attractors, and apply FHNN to the defense against chip cloning attacks for anticounterfeiting. A significant advantage of FHNN is that its attractors essentially relate to the neuron's fractional order. FHNN possesses the fractional-order-stability and fractional-order-sensitivity characteristics.

  17. The Small Wonders of Fractions.

    ERIC Educational Resources Information Center

    May, Lola

    1996-01-01

    Presents five math activities designed to help students understand fractions, keep students motivated, and help them maintain their math skills. The activities are "What's in a Name?""Fractured Words,""Egyptian Fractions,""More Fractured Fractions,""Name the Parts," and "Timely Device."…

  18. Fractional diffusion on bounded domains

    DOE PAGES

    Defterli, Ozlem; D'Elia, Marta; Du, Qiang; ...

    2015-03-13

    We found that the mathematically correct specification of a fractional differential equation on a bounded domain requires specification of appropriate boundary conditions, or their fractional analogue. In this paper we discuss the application of nonlocal diffusion theory to specify well-posed fractional diffusion equations on bounded domains.

  19. Fractional diffusion on bounded domains

    SciTech Connect

    Defterli, Ozlem; D'Elia, Marta; Du, Qiang; Gunzburger, Max Donald; Lehoucq, Richard B.; Meerschaert, Mark M.

    2015-03-13

    We found that the mathematically correct specification of a fractional differential equation on a bounded domain requires specification of appropriate boundary conditions, or their fractional analogue. In this paper we discuss the application of nonlocal diffusion theory to specify well-posed fractional diffusion equations on bounded domains.

  20. How Weird Are Weird Fractions?

    ERIC Educational Resources Information Center

    Stuffelbeam, Ryan

    2013-01-01

    A positive rational is a weird fraction if its value is unchanged by an illegitimate, digit-based reduction. In this article, we prove that each weird fraction is uniquely weird and initiate a discussion of the prevalence of weird fractions.

  1. How Weird Are Weird Fractions?

    ERIC Educational Resources Information Center

    Stuffelbeam, Ryan

    2013-01-01

    A positive rational is a weird fraction if its value is unchanged by an illegitimate, digit-based reduction. In this article, we prove that each weird fraction is uniquely weird and initiate a discussion of the prevalence of weird fractions.

  2. The random continued fraction transformation

    NASA Astrophysics Data System (ADS)

    Kalle, Charlene; Kempton, Tom; Verbitskiy, Evgeny

    2017-03-01

    We introduce a random dynamical system related to continued fraction expansions. It uses random combinations of the Gauss map and the Rényi (or backwards) continued fraction map. We explore the continued fraction expansions that this system produces, as well as the dynamical properties of the system.

  3. Numerical approaches to fractional calculus and fractional ordinary differential equation

    NASA Astrophysics Data System (ADS)

    Li, Changpin; Chen, An; Ye, Junjie

    2011-05-01

    Nowadays, fractional calculus are used to model various different phenomena in nature, but due to the non-local property of the fractional derivative, it still remains a lot of improvements in the present numerical approaches. In this paper, some new numerical approaches based on piecewise interpolation for fractional calculus, and some new improved approaches based on the Simpson method for the fractional differential equations are proposed. We use higher order piecewise interpolation polynomial to approximate the fractional integral and fractional derivatives, and use the Simpson method to design a higher order algorithm for the fractional differential equations. Error analyses and stability analyses are also given, and the numerical results show that these constructed numerical approaches are efficient.

  4. Fractional chemotaxis diffusion equations.

    PubMed

    Langlands, T A M; Henry, B I

    2010-05-01

    We introduce mesoscopic and macroscopic model equations of chemotaxis with anomalous subdiffusion for modeling chemically directed transport of biological organisms in changing chemical environments with diffusion hindered by traps or macromolecular crowding. The mesoscopic models are formulated using continuous time random walk equations and the macroscopic models are formulated with fractional order differential equations. Different models are proposed depending on the timing of the chemotactic forcing. Generalizations of the models to include linear reaction dynamics are also derived. Finally a Monte Carlo method for simulating anomalous subdiffusion with chemotaxis is introduced and simulation results are compared with numerical solutions of the model equations. The model equations developed here could be used to replace Keller-Segel type equations in biological systems with transport hindered by traps, macromolecular crowding or other obstacles.

  5. Soot Volume Fraction Imaging

    NASA Technical Reports Server (NTRS)

    Greenberg, Paul S.; Ku, Jerry C.

    1994-01-01

    A new technique is described for the full-field determination of soot volume fractions via laser extinction measurements. This technique differs from previously reported point-wise methods in that a two-dimensional array (i.e., image) of data is acquired simultaneously. In this fashion, the net data rate is increased, allowing the study of time-dependent phenomena and the investigation of spatial and temporal correlations. A telecentric imaging configuration is employed to provide depth-invariant magnification and to permit the specification of the collection angle for scattered light. To improve the threshold measurement sensitivity, a method is employed to suppress undesirable coherent imaging effects. A discussion of the tomographic inversion process is provided, including the results obtained from numerical simulation. Results obtained with this method from an ethylene diffusion flame are shown to be in close agreement with those previously obtained by sequential point-wise interrogation.

  6. Functional fractionation of platelets.

    PubMed

    Haver, V M; Gear, A R

    1981-02-01

    Studies of platelet populations suggest that they are heterogeneous in size, age, and metabolic parameters. In an attempt to correlate these parameters with efficiency of aggregation, a new technique, functional fractionation, was developed. Platelet populations are separated by their differential reactivity to aggregating agents. For example, low doses of ADP (0.1 to 0.7 microM) are added to stirred PRP, after which gentle centrifugation is used to remove aggregates from single unreacted platelets. The loose aggregates can be readily dispersed for comparison of the physical or biochemical properties of the reacted versus unreacted platelets. It was found that reactive platelets were larger (6.5 micrometer3) than unreacted platelets (5.51 micrometer3). No significant difference in density existed between the two populations, and no release of [14C]serotonin from prelabeled platelets occurred during functional fractionation. Scanning and transmission electron microscopy confirmed the size difference and revealed that in both populations platelets were structurally intact with a normal discoid shape and no significant difference in organelle content. Human platelets most reactive to ADP were also enriched in glycogen (3.6-fold), ATP (1.6-fold), and ADP (twofold), compared with less reactive cells. These "reactive" cells took up more 51[Cr] and contained 1.9 times more surface sialic acid. In an in vivo aging experiment, rats were injected with 75[Se]methionine. Shortly after labeling (1 day), the most reactive platelets possessed the highest amount of 75[Se]. These results reveal that functionally active platelets, which are also larger, are more active metabolically than less reactive platelets, possess a higher negative surface charge, and may be a younger population.

  7. Fraction Reduction in Membrane Systems

    PubMed Central

    Zhang, Hong

    2014-01-01

    Fraction reduction is a basic computation for rational numbers. P system is a new computing model, while the current methods for fraction reductions are not available in these systems. In this paper, we propose a method of fraction reduction and discuss how to carry it out in cell-like P systems with the membrane structure and the rules with priority designed. During the application of fraction reduction rules, synchronization is guaranteed by arranging some special objects in these rules. Our work contributes to performing the rational computation in P systems since the rational operands can be given in the form of fraction. PMID:24772037

  8. Fractionally charged skyrmions in fractional quantum Hall effect.

    PubMed

    Balram, Ajit C; Wurstbauer, U; Wójs, A; Pinczuk, A; Jain, J K

    2015-11-26

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeeman energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region.

  9. Fractionally charged skyrmions in fractional quantum Hall effect

    SciTech Connect

    Balram, Ajit C.; Wurstbauer, U.; Wójs, A.; Pinczuk, A.; Jain, J. K.

    2015-11-26

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeeman energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region.

  10. Rapid flow fractionation of particles combining liquid and particulate dielectrophoresis

    NASA Technical Reports Server (NTRS)

    King, Michael R. (Inventor); Lomakin, Oleg (Inventor); Jones, Thomas B. (Inventor); Ahmed, Rajib (Inventor)

    2007-01-01

    Rapid, size-based, deposition of particles from liquid suspension is accomplished using a nonuniform electric field created by coplanar microelectrode strips patterned on an insulating substrate. The scheme uses the dielectrophoretic force both to distribute aqueous liquid containing particles and, simultaneously, to separate the particles. Size-based separation is found within nanoliter droplets formed along the structure after voltage removal. Bioparticles or macromolecules of similar size can also be separated based on subtle differences in dielectric property, by controlling the frequency of the AC current supplied to the electrodes.

  11. An improved fractional divider for fractional-N frequency synthesizers

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Liu, Yang; Zhou, Yongqi

    2009-07-01

    This paper presents an improved fractional divider used in 1.8~2GHz fractional-N frequency synthesizers. A new clock setting for delta-sigma modulator (DSM) is proposed to prevent the potential problems of traditional fractional dividers: the DSM output would be wrongly loaded and the action of DSM circuit may affect the phase-detection of phase-frequency-detector (PFD). Simulation result shows the effectiveness of this improvement.

  12. Fractional variational calculus in terms of Riesz fractional derivatives

    NASA Astrophysics Data System (ADS)

    Agrawal, O. P.

    2007-06-01

    This paper presents extensions of traditional calculus of variations for systems containing Riesz fractional derivatives (RFDs). Specifically, we present generalized Euler-Lagrange equations and the transversality conditions for fractional variational problems (FVPs) defined in terms of RFDs. We consider two problems, a simple FVP and an FVP of Lagrange. Results of the first problem are extended to problems containing multiple fractional derivatives, functions and parameters, and to unspecified boundary conditions. For the second problem, we present Lagrange-type multiplier rules. For both problems, we develop the Euler-Lagrange-type necessary conditions which must be satisfied for the given functional to be extremum. Problems are considered to demonstrate applications of the formulations. Explicitly, we introduce fractional momenta, fractional Hamiltonian, fractional Hamilton equations of motion, fractional field theory and fractional optimal control. The formulations presented and the resulting equations are similar to the formulations for FVPs given in Agrawal (2002 J. Math. Anal. Appl. 272 368, 2006 J. Phys. A: Math. Gen. 39 10375) and to those that appear in the field of classical calculus of variations. These formulations are simple and can be extended to other problems in the field of fractional calculus of variations.

  13. Accessible solitons of fractional dimension

    SciTech Connect

    Zhong, Wei-Ping; Belić, Milivoj; Zhang, Yiqi

    2016-05-15

    We demonstrate that accessible solitons described by an extended Schrödinger equation with the Laplacian of fractional dimension can exist in strongly nonlocal nonlinear media. The soliton solutions of the model are constructed by two special functions, the associated Legendre polynomials and the Laguerre polynomials in the fraction-dimensional space. Our results show that these fractional accessible solitons form a soliton family which includes crescent solitons, and asymmetric single-layer and multi-layer necklace solitons. -- Highlights: •Analytic solutions of a fractional Schrödinger equation are obtained. •The solutions are produced by means of self-similar method applied to the fractional Schrödinger equation with parabolic potential. •The fractional accessible solitons form crescent, asymmetric single-layer and multilayer necklace profiles. •The model applies to the propagation of optical pulses in strongly nonlocal nonlinear media.

  14. Fractional-time quantum dynamics.

    PubMed

    Iomin, Alexander

    2009-08-01

    Application of the fractional calculus to quantum processes is presented. In particular, the quantum dynamics is considered in the framework of the fractional time Schrödinger equation (SE), which differs from the standard SE by the fractional time derivative: partial differential/partial differentialt --> partial differential(alpha)/partial differentialt(alpha). It is shown that for alpha=1/2 the fractional SE is isospectral to a comb model. An analytical expression for the Green's functions of the systems are obtained. The semiclassical limit is discussed.

  15. Trigonometric Integrals via Partial Fractions

    ERIC Educational Resources Information Center

    Chen, H.; Fulford, M.

    2005-01-01

    Parametric differentiation is used to derive the partial fractions decompositions of certain rational functions. Those decompositions enable us to integrate some new combinations of trigonometric functions.

  16. Trigonometric Integrals via Partial Fractions

    ERIC Educational Resources Information Center

    Chen, H.; Fulford, M.

    2005-01-01

    Parametric differentiation is used to derive the partial fractions decompositions of certain rational functions. Those decompositions enable us to integrate some new combinations of trigonometric functions.

  17. The application of an optically switched dielectrophoretic (ODEP) force for the manipulation and assembly of cell-encapsulating alginate microbeads in a microfluidic perfusion cell culture system for bottom-up tissue engineering.

    PubMed

    Lin, Yen-Heng; Yang, Ya-Wen; Chen, Yi-Dao; Wang, Shih-Siou; Chang, Yu-Han; Wu, Min-Hsien

    2012-03-21

    This study reports the utilisation of an optically switched dielectrophoretic (ODEP) force for the manipulation and assembly of cell-encapsulating alginate microbeads in a microfluidic perfusion cell culture system for bottom-up tissue engineering. One of the key features of this system is the ODEP force-based mechanism, which allows a commercial projector to be coupled with a computer to manipulate and assemble cell-encapsulating microbeads in an efficient, manageable, and user-friendly manner. Another distinctive feature is the design of the microfluidic cell culture chip, which allows the patterned cell-encapsulating microbeads to be cultivated on site under culture medium perfusion conditions. For demonstrating its application in bottom-up cartilage tissue engineering, chondrocyte-encapsulating alginate microbeads varying in encapsulated cell densities were generated. The manipulation forces associated with operating the alginate microbeads were experimentally evaluated. The results revealed that the measured manipulation forces increased with increases in both the applied electric voltage and the number of cells in the alginate microbeads. Nevertheless, the observed manipulation force was found to be independent of the size of the cell-free alginate microbeads. It can be speculated that the friction force may influence the estimation of the ODEP force within the experimental conditions investigated. In this study, chondrocyte-encapsulating alginate microbeads with three different cell densities were manipulated and assembled in the proposed microfluidic system to form a compact sheet-like cell culture construct that imitates the cell distribution in the cross-section of native articular cartilage. Moreover, the demonstration case also showed that the cell viability of the cultured cells in the microfluidic system remained as high as 96 ± 2%. In this study, four sheet-like cell culture constructs were stacked to create a larger assembled cell culture construct

  18. Fractional random walk lattice dynamics

    NASA Astrophysics Data System (ADS)

    Michelitsch, T. M.; Collet, B. A.; Riascos, A. P.; Nowakowski, A. F.; Nicolleau, F. C. G. A.

    2017-02-01

    We analyze time-discrete and time-continuous ‘fractional’ random walks on undirected regular networks with special focus on cubic periodic lattices in n  =  1, 2, 3,.. dimensions. The fractional random walk dynamics is governed by a master equation involving fractional powers of Laplacian matrices {{L}\\fracα{2}}} where α =2 recovers the normal walk. First we demonstrate that the interval 0<α ≤slant 2 is admissible for the fractional random walk. We derive analytical expressions for the transition matrix of the fractional random walk and closely related the average return probabilities. We further obtain the fundamental matrix {{Z}(α )} , and the mean relaxation time (Kemeny constant) for the fractional random walk. The representation for the fundamental matrix {{Z}(α )} relates fractional random walks with normal random walks. We show that the matrix elements of the transition matrix of the fractional random walk exihibit for large cubic n-dimensional lattices a power law decay of an n-dimensional infinite space Riesz fractional derivative type indicating emergence of Lévy flights. As a further footprint of Lévy flights in the n-dimensional space, the transition matrix and return probabilities of the fractional random walk are dominated for large times t by slowly relaxing long-wave modes leading to a characteristic {{t}-\\frac{n{α}} -decay. It can be concluded that, due to long range moves of fractional random walk, a small world property is emerging increasing the efficiency to explore the lattice when instead of a normal random walk a fractional random walk is chosen.

  19. Understanding Magnitudes to Understand Fractions

    ERIC Educational Resources Information Center

    Gabriel, Florence

    2016-01-01

    Fractions are known to be difficult to learn and difficult to teach, yet they are vital for students to have access to further mathematical concepts. This article uses evidence to support teachers employing teaching methods that focus on the conceptual understanding of the magnitude of fractions.

  20. Rational Exponentials and Continued Fractions

    ERIC Educational Resources Information Center

    Denny, J. K.

    2012-01-01

    Using continued fraction expansions, we can approximate constants, such as pi and e, using an appropriate integer n raised to the power x[superscript 1/x], x a suitable rational. We review continued fractions and give an algorithm for producing these approximations.

  1. Dividing Fractions and Problem Solving

    ERIC Educational Resources Information Center

    Cramer, Kathleen; Monson, Debra; Whitney, Stephanie; Leavitt, Seth; Wyberg, Terry

    2010-01-01

    Fraction division is generally introduced in sixth or seventh grade with this rule: "Invert and multiply." The authors examined current commercial curricula and found that few textbooks use context as a way to build meaning for the division of fractions. When context is used, the connection between the invert-and-multiply rule and the context is…

  2. Unwrapping Students' Ideas about Fractions

    ERIC Educational Resources Information Center

    Lewis, Rebecca M.; Gibbons, Lynsey K.; Kazemi, Elham; Lind, Teresa

    2015-01-01

    Supporting students to develop an understanding of the meaning of fractions is an important goal of elementary school mathematics. This involves developing partitioning strategies, creating representations, naming fractional quantities, and using symbolic notation. This article describes how teachers can use a formative assessment problem to…

  3. Rational Exponentials and Continued Fractions

    ERIC Educational Resources Information Center

    Denny, J. K.

    2012-01-01

    Using continued fraction expansions, we can approximate constants, such as pi and e, using an appropriate integer n raised to the power x[superscript 1/x], x a suitable rational. We review continued fractions and give an algorithm for producing these approximations.

  4. Understanding Magnitudes to Understand Fractions

    ERIC Educational Resources Information Center

    Gabriel, Florence

    2016-01-01

    Fractions are known to be difficult to learn and difficult to teach, yet they are vital for students to have access to further mathematical concepts. This article uses evidence to support teachers employing teaching methods that focus on the conceptual understanding of the magnitude of fractions.

  5. Unwrapping Students' Ideas about Fractions

    ERIC Educational Resources Information Center

    Lewis, Rebecca M.; Gibbons, Lynsey K.; Kazemi, Elham; Lind, Teresa

    2015-01-01

    Supporting students to develop an understanding of the meaning of fractions is an important goal of elementary school mathematics. This involves developing partitioning strategies, creating representations, naming fractional quantities, and using symbolic notation. This article describes how teachers can use a formative assessment problem to…

  6. Fractionated Spacecraft Architectures Seeding Study

    DTIC Science & Technology

    2006-04-03

    Multi-attribute Trade- Space Exploration The fractionated spacecraft concept is investigated using Multi-attribute Trade- Space Exploration . This method...Spacecraft Payload Bus Subsystems Payload Module Infrastructure Modules To the Fractionated Spacecraft Multi-Attribute Trade- Space Exploration 1...spacecraft (white blocks) and additional hardware (blue blocks). III. CONCEPT ASSESSMENT METHOD 1. Multi-attribute Trade- Space Exploration The

  7. A new fractional wavelet transform

    NASA Astrophysics Data System (ADS)

    Dai, Hongzhe; Zheng, Zhibao; Wang, Wei

    2017-03-01

    The fractional Fourier transform (FRFT) is a potent tool to analyze the time-varying signal. However, it fails in locating the fractional Fourier domain (FRFD)-frequency contents which is required in some applications. A novel fractional wavelet transform (FRWT) is proposed to solve this problem. It displays the time and FRFD-frequency information jointly in the time-FRFD-frequency plane. The definition, basic properties, inverse transform and reproducing kernel of the proposed FRWT are considered. It has been shown that an FRWT with proper order corresponds to the classical wavelet transform (WT). The multiresolution analysis (MRA) associated with the developed FRWT, together with the construction of the orthogonal fractional wavelets are also presented. Three applications are discussed: the analysis of signal with time-varying frequency content, the FRFD spectrum estimation of signals that involving noise, and the construction of fractional Harr wavelet. Simulations verify the validity of the proposed FRWT.

  8. Radiating subdispersive fractional optical solitons

    SciTech Connect

    Fujioka, J. Espinosa, A.; Rodríguez, R. F.; Malomed, B. A.

    2014-09-01

    It was recently found [Fujioka et al., Phys. Lett. A 374, 1126 (2010)] that the propagation of solitary waves can be described by a fractional extension of the nonlinear Schrödinger (NLS) equation which involves a temporal fractional derivative (TFD) of order α > 2. In the present paper, we show that there is also another fractional extension of the NLS equation which contains a TFD with α < 2, and in this case, the new equation describes the propagation of radiating solitons. We show that the emission of the radiation (when α < 2) is explained by resonances at various frequencies between the pulses and the linear modes of the system. It is found that the new fractional NLS equation can be derived from a suitable Lagrangian density, and a fractional Noether's theorem can be applied to it, thus predicting the conservation of the Hamiltonian, momentum and energy.

  9. Radiating subdispersive fractional optical solitons

    NASA Astrophysics Data System (ADS)

    Fujioka, J.; Espinosa, A.; Rodríguez, R. F.; Malomed, B. A.

    2014-09-01

    It was recently found [Fujioka et al., Phys. Lett. A 374, 1126 (2010)] that the propagation of solitary waves can be described by a fractional extension of the nonlinear Schrödinger (NLS) equation which involves a temporal fractional derivative (TFD) of order α > 2. In the present paper, we show that there is also another fractional extension of the NLS equation which contains a TFD with α < 2, and in this case, the new equation describes the propagation of radiating solitons. We show that the emission of the radiation (when α < 2) is explained by resonances at various frequencies between the pulses and the linear modes of the system. It is found that the new fractional NLS equation can be derived from a suitable Lagrangian density, and a fractional Noether's theorem can be applied to it, thus predicting the conservation of the Hamiltonian, momentum and energy.

  10. Fractional active disturbance rejection control.

    PubMed

    Li, Dazi; Ding, Pan; Gao, Zhiqiang

    2016-05-01

    A fractional active disturbance rejection control (FADRC) scheme is proposed to improve the performance of commensurate linear fractional order systems (FOS) and the robust analysis shows that the controller is also applicable to incommensurate linear FOS control. In FADRC, the traditional extended states observer (ESO) is generalized to a fractional order extended states observer (FESO) by using the fractional calculus, and the tracking differentiator plus nonlinear state error feedback are replaced by a fractional proportional-derivative controller. To simplify controller tuning, the linear bandwidth-parameterization method has been adopted. The impacts of the observer bandwidth ωo and controller bandwidth ωc on system performance are then analyzed. Finally, the FADRC stability and frequency-domain characteristics for linear single-input single-output FOS are analyzed. Simulation results by FADRC and ADRC on typical FOS are compared to demonstrate the superiority and effectiveness of the proposed scheme.

  11. Arsenic speciation in the dispersible colloidal fraction of soils from a mine-impacted creek.

    PubMed

    Serrano, Susana; Gomez-Gonzalez, Miguel Angel; O'Day, Peggy A; Laborda, Francisco; Bolea, Eduardo; Garrido, Fernando

    2015-04-09

    Arsenic and iron speciation in the dispersible colloid fraction (DCF; 10-1000 nm) from an As-rich mine waste pile, sediments of a streambed that collects runoff from waste pile, the streambed subsoil, and the sediments of a downstream pond were investigated by combining asymmetrical-flow field-flow fractionation (AsFlFFF)/inductively-coupled plasma-mass spectrometry (ICP-MS), transmission electron microscopy (TEM) and X-ray absorption (XAS) spectroscopy. Calcium, Fe and As (Fe/As molar ratio ∼ 1) were the main components of the DCF from waste pile. TEM/EDS and As and Fe XAS analysis revealed the presence of nanoparticle scorodite in this same DCF, as well as Fe nanoparticles in all samples downstream of the waste pile. Arsenic and Fe XAS showed As(V) adsorbed onto nanoparticulate ferrihydrite in the DCF of downstream samples. Micro-X-ray fluorescence indicated a strong correlation between Fe and As in phyllosilicate/Fe(3+) (oxi) hydroxide aggregates from the sediment pond. Fractionation analysis showed the mean particle size of the DCF from the streambed sample to be smaller than that of the streambed subsoil and sediment ponds samples. These results show that an important and variable fraction of As may be bound to dispersible colloids that can be released from contaminated soils and transported downstream in natural systems.

  12. Fractionally charged skyrmions in fractional quantum Hall effect

    DOE PAGES

    Balram, Ajit C.; Wurstbauer, U.; Wójs, A.; ...

    2015-11-26

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeemanmore » energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region.« less

  13. Upgrading petroleum and petroleum fractions

    SciTech Connect

    Ferguson, S.; Reese, D.D.

    1988-06-21

    A method is described for neutralizing the organic naphthenic acids acidity present in petroleum and petroleum fractions to produce a neutralization number less than 1.0 whereby they are rendered suitable as lube oil feed stocks which consists essentially of treating the petroleum and petroleum fractions with a neutralizing amount of monoethanolamine to form an amine salt with the organic acids and then heating the thus-neutralized petroleum and petroleum fractions at a temperature at least about 25/sup 0/F greater than the boiling point of water and for a time sufficient to convert the amine salts to amides.

  14. Recalcitrant dissolved organic carbon fractions.

    PubMed

    Hansell, Dennis A

    2013-01-01

    Marine dissolved organic carbon (DOC) exhibits a spectrum of reactivity, from very fast turnover of the most bioavailable forms in the surface ocean to long-lived materials circulating within the ocean abyss. These disparate reactivities group DOC by fractions with distinctive functions in the cycling of carbon, ranging from support of the microbial loop to involvement in the biological pump to a hypothesized major source/sink of atmospheric CO(2) driving paleoclimate variability. Here, the major fractions constituting the global ocean's recalcitrant DOC pool are quantitatively and qualitatively characterized with reference to their roles in carbon biogeochemistry. A nomenclature for the fractions is proposed based on those roles.

  15. Weyl quantization of fractional derivatives

    SciTech Connect

    Tarasov, Vasily E.

    2008-10-15

    The quantum analogs of the derivatives with respect to coordinates q{sub k} and momenta p{sub k} are commutators with operators P{sub k} and Q{sub k}. We consider quantum analogs of fractional Riemann-Liouville and Liouville derivatives. To obtain the quantum analogs of fractional Riemann-Liouville derivatives, which are defined on a finite interval of the real axis, we use a representation of these derivatives for analytic functions. To define a quantum analog of the fractional Liouville derivative, which is defined on the real axis, we can use the representation of the Weyl quantization by the Fourier transformation.

  16. Australia's Next Top Fraction Model

    ERIC Educational Resources Information Center

    Gould, Peter

    2013-01-01

    Peter Gould suggests Australia's next top fraction model should be a linear model rather than an area model. He provides a convincing argument and gives examples of ways to introduce a linear model in primary classrooms.

  17. Fractional Transmission Line with Losses

    NASA Astrophysics Data System (ADS)

    Gómez-Aguilar, José Francisco; Dumitru, Baleanu

    2014-11-01

    In this manuscript, the fractional transmission line with losses is presented. The order of the Caputo derivative is considered as 0 < β ≤ 1 and 0 < γ ≤ 1 for the fractional equation in space and time domain, respectively. Two cases are solved, with fractional spatial and fractional temporal derivatives, and also numerical simulations were carried out, where there are taken both derivatives in simultaneous form. Two parameters σx and σt are introduced and a physical relation between these parameters is reported. Solutions in space and time are given in terms of the Mittag-Leffler functions. The classic cases are recovered when β and γ are equal to 1.

  18. Commercial SNF Accident Release Fractions

    SciTech Connect

    J. Schulz

    2004-11-05

    The purpose of this analysis is to specify and document the total and respirable fractions for radioactive materials that could be potentially released from an accident at the repository involving commercial spent nuclear fuel (SNF) in a dry environment. The total and respirable release fractions are used to support the preclosure licensing basis for the repository. The total release fraction is defined as the fraction of total commercial SNF assembly inventory, typically expressed as an activity inventory (e.g., curies), of a given radionuclide that is released to the environment from a waste form. Radionuclides are released from the inside of breached fuel rods (or pins) and from the detachment of radioactive material (crud) from the outside surfaces of fuel rods and other components of fuel assemblies. The total release fraction accounts for several mechanisms that tend to retain, retard, or diminish the amount of radionuclides that are available for transport to dose receptors or otherwise can be shown to reduce exposure of receptors to radiological releases. The total release fraction includes a fraction of airborne material that is respirable and could result in inhalation doses; this subset of the total release fraction is referred to as the respirable release fraction. Accidents may involve waste forms characterized as: (1) bare unconfined intact fuel assemblies, (2) confined intact fuel assemblies, or (3) canistered failed commercial SNF. Confined intact commercial SNF assemblies at the repository are contained in shipping casks, canisters, or waste packages. Four categories of failed commercial SNF are identified: (1) mechanically and cladding-penetration damaged commercial SNF, (2) consolidated/reconstituted assemblies, (3) fuel rods, pieces, and debris, and (4) nonfuel components. It is assumed that failed commercial SNF is placed into waste packages with a mesh screen at each end (CRWMS M&O 1999). In contrast to bare unconfined fuel assemblies, the

  19. Concurrent fractional and equilibrium crystallisation

    NASA Astrophysics Data System (ADS)

    Sha, Lian-Kun

    2012-06-01

    This paper proposes the concept of concurrent fractional and equilibrium crystallisation (CFEC) in a multi-phase magmatic system in light of experimental results on diffusivities of elements and other species in minerals and melts. A group of equations are presented to describe how the concentrations of an element or isotope change in fractionated solid, equilibrated solid, melt, liquid, and gas phases, as well as in magma, as a function of distribution coefficients and mass fractions during the CFEC process. CFEC model is a generalised and unified formulation that is valid, not only for pure fractional crystallisation (FC) and perfect equilibrium crystallisation (EC) singly, as two of its limiting end-member cases, but also for the geologically more important process of concurrent fractional and equilibrium crystallisation. The concept that both fractional and equilibrium crystallisation can operate concurrently in a magmatic system, for a given element, among different minerals, and even within different-sized crystal grains of the very same mineral phase, is of fundamental importance in deepening our current understanding of magmatic differentiation processes. CFEC probably occurs more frequently in the natural world than either pure fractional or perfect equilibrium crystallisation alone, as a result of the interplay of varying diffusivities of elements under diverse physicochemical conditions, different residence time and growth rates of mineral phases in magmas, and varying grain sizes within each phase and among different phases. The marked systematic variations in trace element concentrations in the melts of the Bishop Tuff have long been perplexing and difficult to reconcile with existing models of differentiation. CFEC, which is able to better explain the scatter trends in a systematic way than fractional crystallisation, is considered to be the cause.

  20. Fractional Charge Definitions and Conditions

    SciTech Connect

    Goldhaber, A.S.

    2004-06-04

    Fractional charge is known through theoretical and experimental discoveries of isolable objects carrying fractions of familiar charge units--electric charge Q, spin S, and the difference of baryon and lepton numbers B-L. With a few simple assumptions all these effects may be described using a generalized version of charge renormalization for locally conserved charges, in which medium correlations yield familiar adiabatic, continuous renormalization, or sometimes nonadiabatic, discrete renormalization. Fractional charges may be carried by fundamental particles or fundamental solitons. Either picture works for the simplest fractional-quantum-Hall-effect quasiholes, though the particle description is far more general. The only known fundamental solitons in three or fewer space dimensions d are the kink (d = 1), the vortex (d = 2), and the magnetic monopole (d = 3). Further, for a charge not intrinsically coupled to the topological charge of a soliton, only the kink and the monopole may carry fractional values. The same reasoning enforces fractional values of B-L for electrically charged elementary particles.