433 research outputs found
Quantitative Splitt Fractionation of Lagoon Sediments
No full textIn this work, SPLITT Fractionation (split flow thin cell) is used to sort hydrodynamically sedimented particles coming from the Sacca di Goro, a lagoon-like system close to the Po River delta (Italy). First the possibility of performing quantitative mass separations with a SPLITT cell apparatus was checked on a standard silica sample of known particle size distribution (PSD).
Environmental sediment samples and relative SPLITT sub-fractions were subject to Inductive Coupled Plasma – Atomic Emission Spectroscopy (ICP-AES) characterization for the following elements: Al, Fe, Cd, Cr, Cu, Ni, Mn, Pb and Zn. The distribution of these metals by particle size fractions has been investigated. The accuracy of the entire separation procedure has been also evaluated
Analytical SPLITT cell fractionation: Linearity and resolution study.
No full textIn this paper the analytical SPLITT (split flow thin cell) procedure is used to characterize the percentage composition of micronic polydisperse particulate samples at a given cut-off size. The linearity and resolution of the separation method have been
tested using specifically prepared starch samples, in order to compare the analytical process with two continuous (preparative) SPLITT procedures. Linearity has been checked by injecting a series of suspensions (at different concentrations) under five
different flow rate conditions. Retrieval factors F were evaluated to verify the relative amount of sample exiting the cell outlets. The effective resolution has been assessed by inspecting the SPLITT fractions with an optical microscope, counting the granules, and evaluating the percentage of granules of expected size. It has been found that the resolution is very good (around 90%) and independent of sample distribution. It is seen from the comparison that in the analytical SPLITT mode sample resolution is usually around 85–90% and it is significantly better than that of the continuous SPLITT modes, thus making the analytical mode valuable in characterizing polydisperse samples. The method was tested for the characterization of a commercial
starch sample
Modelo físico para la separación de células en un canal Step-SPLITT
No full textEl propósito de este trabajo fue explicar la separación de las poblaciones celulares presentes en un cultivo primario de células de Schwann obtenidas a partir de nervio periférico de ratón, con un modelo físico basado en los principios que sustentan la separación de especies químicas y partículas de la técnica Split-Flow Lateral-Transpor Thin Fractionation (SPLITT), desarrollada en Estados Unidos en los años 80. El modelo permitió en el caso gravitacional, con la solución de las ecuaciones de movimiento de las células, determinar a priori que el flujo totalAbstract. The purpose of this work was to explain the fractionation of cell populations present in a primary culture of Schwann cells dissociated from peripheral nerve of mice, with a physical model based on the principals of separation technique of chemical species and particles called Split-Flow Lateral-Transport Thin Fractionation (SPLITT), development in U.S.A in the 80s. By solving the movement equations for these cells, the theoretical model allowed in the gravitational case, the a priori determination of the total flowMaestrí
Modelo físico de los parámetros y efectos hidrodinámicos involucrados en una separación óptima de células usando una técnica campo-flujo (s-splitt)
No full textEste trabajo reporta un modelo de separación y los parámetros físicos necesarios para enriquecer fracciones de un organelo intracelular llamado vacuola parasitófora PV. La PV es generada al interior de macrófagos (células del sistema inmune) de la línea celular J774.A1 al ser infectados por el parásito Leishmania amazonensis. Para la separación se usó la técnica de separación hidrodinámica llamada Splitt thin flow fractionation acoplada a una celda de separación Step-Splitt. Se determinaron los parámetros propios (densidad, tamaño, forma), de esta línea celular sin infección, en infección por el parásito L. amazonensis y luego de ruptura mecánica. Además se determinaron las propiedades físicas del fluido transportador en el dispositivo Step-Splitt (densidad, viscosidad dinámica) a dos temperaturas diferentes en el rango fisiológico. Con el hallazgo de estos parámetros y con criterios de sedimentación gravitacional de los cuerpos celulares se diseñó, construyó y simuló mediante el paquete CFD Fluent® la celda de separación, para analizar la estabilidad hidrodinámica y los parámetros que optimizan la separación de estos organelos celulares.This manuscript reports a fractionation model using a hydrodynamic cell separation technique called Splitt Thin Flow (SPLITT) coupled to a Step-Splitt mechanism to separate a fraction of an intracellular organelle called the parasitophorous vacuole (PV) of Leishmania amazonesis. It reports the physical parameters involved in the enrichment of PVs which are generated inside macrophages (immune system cells) after interaction with the parasite Leishmania. The physical parameters (density, size, shape) of the macrophage-like mammalian cell line J774.A1 were measured in control conditions and after infection. Differences in density, size and shape were found between these two groups of cells and after mechanical disruption of infected cells. The physical parameters of the carrier fluid (density and dynamical viscosity) were also measured at two different temperatures within the physiological range. Based on the parameters found and gravitational sedimentation criteria over the cell bodies, a Step Splitt cell was designed built and simulated using the CFD Fluent® Package to analyze the hydrodynamic stability and the potential parameters to achieve organelle separation.Maestrí
Characterization of a microscale cross-flow based split flow then fractionation (Splitt)
No full textthesisA growing need for the separation of nanoparticles may be solved by split flow thin cell fractionation (SPLITT). This work introduces a novel cross-flow based SPLITT microsystem that is capable of high-speed continuous separations based on the size of particles in the sample. Flow-SPLITT is a new member of the SPLITT/FFF family of techniques and uses cross-flow as the driving field and has the potential to be more efficient than diffusion SPLITT or H-filter technology. An asymmetrical cross-flow based SPLITT system has been used to purify 130 nm, 220 nm polystyrene nanoparticles and Bovine Serum Albumin in less than 15 minutes. The work will describe the design, fabrication, and characterization of this new separation technique that is capable of small molecular weight biological separations. A cross-flow is used to induce a "separation field". The cross-flow is drawn out of the channel along its length at a given flowrate. In addition, the inlet flowrates are also arranged such that sample particles are further pushed towards the frit-membrane wall. Most of the sample particles will elute from the outlet a and only the smaller particles in a given size range (larger than the pores of membrane wall) will diffuse and cross the inlet splitting plane and be collected at the outlet b. The cross-flow SPLITT microsystem consists of two fluidic channels that are separated by a splitter layer made of a stiff Mylar sheet. One side of the flow unit utilizes a porous frit that allows for cross-flow in or out of the channel as one wall and glass slide as another wall and push-pull syringe pumps have been used for flowing the buffer solution and a t-injector and microliter syringe are to inject the sample for preliminary characterization of the system. Standard fittings are used to connect the microsystem and the syringe pumps. Future work will involve optimizing the flowrate combinations for improved and continuous separation of more complex samples
On-line particle concentrator with upstream ultrafiltration in continuous SPLITT fractionation
No full textAn upstream ultrafiltration (UU) method is employed for the on-line concentration of collected particle fraction and for the convenient regulation of flow rates in split-now thin (SPLITT) fractionation. Concentration of the collected particle fraction is necessary to fractionate particles by smaller cutoff diameters in SPLITT fractionation. By introducing a simple device utilizing upstream ultrafiltration with tangential now, particle solution collected at each SPLITT outlet can be simultaneously concentrated within the device during the run without the need of a separate centrifugation. Since a needle valve can be implemented at the outlet of the particle concentrator using upstream ultrafiltration (PCUU), it provides a great convenience with an accuracy in adjusting outlet now rates of the SPLITT channel, and it eventually brings accurate control of cutoff diameter in SPLITT fractionation of a nnicrometersized particle sample. Moreover, the volume of carrier solution required for SPLITT fractionation, especially for a high-speed SPLITT run, can be minimized by circulating the filtrate solution of PCUU into the carrier reservoir directly. The advantage of on-line particle concentration is demonstrated by utilizing a slow flow feed technique for the fractionation of an incinerator fly ash particle sample to obtain a highly efficient SPLITT separation.X1113sciescopu
A Microfluidic SPLITT Device for Fractionating Low-Molecular Weight Samples
No full textIn
this article, we report the design of a microfluidic split flow
thin cell (SPLITT) fractionation device with internal electrodes placed
across the width of its analysis channel for assaying low-molecular
weight samples. The reported device allows the realization of lateral
electric fields and separation distances of the orders of 100 V/cm
and 500 μm, respectively, that are suitable for fractionating
such mixtures with high resolution. Our experiments show that a key
challenge to realizing electrophoretic fractionations using the current
design is to minimize the electroosmotically driven fluid circulations
in its SPLITT channel that tend to hydrodynamically mix the liquid
streams flowing through this duct. The present work addresses this
challenge by chemically modifying the surface of our fluidic conduits
with a new coating medium, N-(2-triethoxysilylpropyl)
formamide, which has been shown to diminish electroosmotic flow in
glass microchannels by over 5 orders of magnitude. Finally, we describe
the integration of the reported microfluidic fractionation device
to a mass spectrometer via the electrospray ionization interface to
allow inline label-free detection of analytes in our assay. Product
purity greater than 95% has been accomplished using the SPLITT system
presented here for a sample of peptides having the same electrical
polarity
A Miniaturized SPLITT System for On-Line Protein Separation
No full textThe development of a microfluidic module for on-line protein separation is presented in this paper. The device is based on the SPLITT (Split flow Thin fractionation) technique and the separation of proteins is electrically driven by means of two platinum electrodes included in the structure of the microdevice. The microfluidic network is realized by means of a thin dry film structure, Ordyl SY 355, (thermo-compression lamination), laminated on three levels, which is patterned through a photolithographic technique. The device has been tested with a Bovine Serum Albumin (BSA) solution, through absorbance measurements with a spectrophotometer, with best achieved separation at the outlet of 40%, measured as relative concentration unbalance at output channels
Acute hydrodynamic damage induced by SPLITT fractionation and centrifugation in red blood cells
No full textThough blood bank processing traditionally employs centrifugation, new separation techniques may be appealing for large scale processes. Split-flow fractionation (SPLITT) is a family of techniques that separates in absence of labelling and uses very low flow rates and force fields, and is therefore expected to minimize cell damage. However, the hydrodynamic stress and possible consequent damaging effects of SPLITT fractionation have not been yet examined. The aim of this study was to investigate the hydrodynamic damage of SPLITT fractionation to human red blood cells, and to compare these effects with those induced by centrifugation. Peripheral whole blood samples were collected from healthy volunteers. Samples were diluted in a buffered saline solution, and were exposed to SPLITT fractionation (flow rates 1-10 ml/min) or centrifugation (100-1500 g) for 10 min. Cell viability, shape, diameter, mean corpuscular hemoglobin, and membrane potential were measured. Under the operating conditions employed, both SPLITT and centrifugation maintained cell viability above 98%, but resulted in significant sublethal damage, including echinocyte formation, decreased cell diameter, decreased mean corpuscular hemoglobin, and membrane hyperpolarization which was inhibited by EGTA. Wall shear stress and maximum energy dissipation rate showed significant correlation with lethal and sublethal damage. Our data do not support the assumption that SPLITT fractionation induces very low shear stress and is innocuous to cell function. Some changes in SPLITT channel design are suggested to minimize cell damage. Measurement of membrane potential and cell diameter could provide a new, reliable and convenient basis for evaluation of hydrodynamic effects on different cell models, allowing identification of optimal operating conditions on different scales. © 2016 Elsevier B.V
Buoyancy-Driven Continuous SPLITT Fractionation: A New Technique for Separation of Microspheres
No full textA new method of Continuous Fractionation using a SPLITT cell is conceived, developed, and tested, and is demonstrated to be useful for separation of collections of particles with different sizes and densities. With this previously uninvestigated mode of operation, this is accomplished for particles by buoyancy-driven separation. Some of the capabilities of this system are illustrated by successful separations of different-sized fluorescent polymer microspheres, with different carrier densities. The resulting experimentally-measured fraction recovery variations are then in good agreement with theoretical calculation from buoyancy-driven SPLITT theory. © Taylor and Francis Group
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