Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 103
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Artigo em Inglês | MEDLINE | ID: mdl-31176269

RESUMO

Plant polyphenols can form functional coatings on various materials through self-polymerization. In this paper, a series of modified capillary columns, which possess diversity of charge characteristics for modulating electroosmotic flow (EOF), were prepared by one-step co-deposition of gallic acid (GA), a plant-derived polyphenol monomer, and branched polyethyleneimine (PEI). The physicochemical properties of the prepared columns were characterized by Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy and scanning electron microscopy (SEM). The magnitude and direction of EOF of GA/PEI co-deposited columns were modulated by changing a series of coating parameters, such as post-incubation of FeCl3, co-deposition time, and deposited amounts of GA and PEI with different relative molecular mass (PEI-600, PEI-1800, PEI-10000, and PEI-70000). Furthermore, the separation efficiencies of the prepared GA/PEI co-deposited columns were evaluated by separations of small molecules, including organic acids, polar nucleotides, phenols, nucleic acid bases and nucleosides. Results indicated that modulating of EOF plays an important role in enhancing the separation performance and reversing the elution order of the analytes. Finally, the developed method was successfully applied to quantitative analysis of acidic compounds in four real samples. The recoveries were in the range of 73.5%-85.8% for citric acid, benzoic acid, sorbic acid, salicylic acid and ascorbic acid in beverage and fruit samples, 101.6%-104.9% for cinnamic acid, vanillic acid, and ferulic acid in Angelica sinensis sample, while 84.6%-97.8% for guanosine-5'-monophosphate, uridine-5'-monophosphate, cytosine-5'- monophosphate and adenosine-5'-monophosphate in Cordyceps samples. These results indicated that the co-deposition of plant polyphenol-inspired GA/PEI coatings can provide new opportunities for EOF modulation of capillary electrophoresis.


Assuntos
Eletrocromatografia Capilar/métodos , Eletro-Osmose/métodos , Ácido Gálico/química , Polietilenoimina/química , Eletrocromatografia Capilar/instrumentação , Eletro-Osmose/instrumentação , Peso Molecular , Ácidos Nucleicos/isolamento & purificação , Nucleosídeos/isolamento & purificação , Nucleotídeos/isolamento & purificação , Compostos Orgânicos/isolamento & purificação , Polimerização
2.
Electrophoresis ; 40(16-17): 2149-2156, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30916400

RESUMO

In this work, an efficient electroosmotic pump (EOP) based on the ultrathin silica nanoporous membrane (u-SNM), which can drive the motion of fluid under the operating voltage as low as 0.2 V, has been fabricated. Thanks to the ultrathin thickness of u-SNM (∼75 nm), the effective electric field strength across u-SNM could be as high as 8.27 × 105 V m-1 in 0.4 M KCl when 1.0 V of voltage was applied. The maximum normalized electroosmotic flow (EOF) rate was as high as 172.90 mL/min/cm2 /V, which was larger than most of other nanoporous membrane based EOPs. In addition to the ultrathin thickness, the high porosity of this membrane (with a pore density of 4 × 1012 cm-2 , corresponding to a porosity of 16.7%) also contribute to such a high EOF rate. Moreover, the EOF rate was found to be proportional to both the applied voltage and the electrolyte concentration. Because of small electrokinetic radius of u-SNM arising from its ultrasmall pore size (ca. 2.3 nm in diameter), the EOF rate increased with increasing the electrolyte concentration and reached the maximum at a concentration of 0.4 M. This dependence was rationalized by the variations of both zeta potential and electrokinetic radius with the electrolyte concentration.


Assuntos
Eletro-Osmose/instrumentação , Membranas Artificiais , Nanoporos , Dióxido de Silício/química , Eletro-Osmose/métodos , Desenho de Equipamento , Modelos Químicos , Porosidade
3.
Electrophoresis ; 40(10): 1387-1394, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30346029

RESUMO

Insulator-based dielectrophoresis has to date been almost entirely restricted to Newtonian fluids despite the fact that many of the chemical and biological fluids exhibit non-Newtonian characteristics. We present herein an experimental study of the fluid rheological effects on the electroosmotic flow of four types of polymer solutions, i.e., 2000 ppm xanthan gum (XG), 5% polyvinylpyrrolidone (PVP), 3000 ppm polyethylene oxide (PEO), and 200 ppm polyacrylamide (PAA) solutions, through a constriction microchannel under DC electric fields of up to 400 V/cm. We find using particle streakline imaging that the fluid elasticity does not change significantly the electroosmotic flow pattern of weakly shear-thinning PVP and PEO solutions from that of a Newtonian solution. In contrast, the fluid shear-thinning causes multiple pairs of flow circulations in the weakly elastic XG solution, leading to a central jet with a significantly enhanced speed from before to after the channel constriction. These flow vortices are, however, suppressed in the strongly viscoelastic and shear-thinning PAA solution.


Assuntos
Eletro-Osmose/métodos , Soluções/química , Resinas Acrílicas/química , Elasticidade , Eletro-Osmose/instrumentação , Técnicas Analíticas Microfluídicas/instrumentação , Polietilenoglicóis/química , Polissacarídeos Bacterianos/química , Povidona/química , Substâncias Viscoelásticas/química
4.
Methods Mol Biol ; 1906: 65-78, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30488385

RESUMO

Electrophoretic on-line sample preconcentration techniques in microfluidic channels improve the sensitivity prior to the separation. Among various techniques, the most important field-amplified sample stacking and sweeping on cross-channel microchips are demonstrated. As a novel microfluidic preconcentration approach, a large-volume sample stacking with electroosmotic flow pump (LVSEP) on straight-channel chips is also presented, which can omit a complicated voltage program for sample injection processes. In this chapter, we describe how to prepare and how to run these on-line sample preconcentration methods in microchip electrophoresis.


Assuntos
Eletro-Osmose/instrumentação , Eletroforese em Microchip/métodos , Tampões (Química) , Calibragem , Eletro-Osmose/métodos , Eletroforese em Microchip/instrumentação , Limite de Detecção , Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos
5.
Electrophoresis ; 40(6): 979-992, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30256428

RESUMO

Induced-charge electroosmosis (ICEO) has attracted tremendous popularity for driving fluid motion from the microfluidic community since the last decade, while less attention has been paid to ICEO-based nanoparticle manipulation. We propose herein a unique concept of hybrid electroosmotic kinetics (HEK) in terms of bi-phase ICEO (BICEO) actuated in a four-terminal spiral electrode array, for effective electrokinetic enrichment of fluorescent polystyrene nanoparticles on ideally polarizable metal strips. First, by alternating the applied AC voltage waves between consecutive discrete terminals, the flow stagnation lines where the sample nanoparticles aggregate can be switched in time between two different distribution modes. Second, we innovatively introduce the idea of AC field-effect flow control on BICEO; by altering the combination of gating voltage sequence, not only the number of circulative particle trapping lines is doubled, but the collecting locations can be flexibly reconfigured as well. Third, hydrodynamic streaming of DC-biased BICEO is tested in our device design, wherein the global linear electroosmosis dominates BICEO contributed from both AC and DC components, resulting in a reduction of particle enrichment area, while with a sharp increase in sample transport speed inside the bulk phase. The flow field associated with HEK is predicted using a linear asymptotic analysis under Debye-Huckel limit, with the simulation results in qualitative agreement with in-lab observations of nanoparticle trapping by exploiting a series of improved ICEO techniques. This work provides an affordable and field-deployable platform for real-time nanoparticle trapping in the context of dilute electrolyte.


Assuntos
Eletro-Osmose/instrumentação , Técnicas Analíticas Microfluídicas/instrumentação , Nanopartículas/química , Eletricidade , Eletro-Osmose/métodos , Desenho de Equipamento , Cinética , Microeletrodos
6.
Sci Rep ; 8(1): 14942, 2018 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-30297764

RESUMO

Dielectrophoresis (DEP) is usually effective close to the electrode surface. Several techniques have been developed to overcome its drawbacks and to enhance dielectrophoretic particle capture. Here we present a simple technique of superimposing alternating current DEP (high-frequency signals) and electroosmosis (EO; low-frequency signals) between two coplanar electrodes (gap: 25 µm) using a lab-made voltage adder for rapid and selective concentration of bacteria, viruses, and proteins, where we controlled the voltages and frequencies of DEP and EO separately. This signal superimposition technique enhanced bacterial capture (Escherichia coli K-12 against 1-µm-diameter polystyrene beads) more selectively (>99%) and rapidly (~30 s) at lower DEP (5 Vpp) and EO (1.2 Vpp) potentials than those used in the conventional DEP capture studies. Nanometer-sized MS2 viruses and troponin I antibody proteins were also concentrated using the superimposed signals, and significantly more MS2 and cTnI-Ab were captured using the superimposed signals than the DEP (10 Vpp) or EO (2 Vpp) signals alone (p < 0.035) between the two coplanar electrodes and at a short exposure time (1 min). This technique has several advantages, such as simplicity and low cost of electrode fabrication, rapid and large collection without electrolysis.


Assuntos
Eletro-Osmose/instrumentação , Escherichia coli K12/isolamento & purificação , Levivirus/isolamento & purificação , Poliestirenos/química , Proteínas/isolamento & purificação , Eletricidade , Eletrodos , Desenho de Equipamento
7.
Electrophoresis ; 39(19): 2460-2470, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30004128

RESUMO

This study uses negative dielectrophoresis and AC electroosmosis as a driving mechanism and presents an electrically driven microconcentrator that concentrates the sample in the region exterior to the electrodes (termed as exterior-electrode electrically driven microconcentrator in this paper). The proposed microconcentrator uses a 3-D face-to-face electrode pair; the top electrode is a relatively large planar electrode, and the bottom electrode is formed with three to six long and thin electrodes connected into an open ring. The sample is brought to the vicinity of the open electrode at the bottom by electroosmotic flow; then, negative dielectrophoresis is used to push the sample away from the electrode and concentrate it in the region surrounded by the open ring electrode. Concentration using an exterior-electrode electrically driven microconcentrator offers promise for convenient use in conjunction with relevant detection systems. The results indicate that for the proposed exterior-electrode electrically driven microconcentrator, the optimal frequency is 100 kHz and the optimal voltage is 13 Vp-p . The corner concentration process at the corners of the bottom open electrodes enables the multi-corner electrodes to exhibit better concentration results than that exhibited by semicircular-shaped electrodes. The concentration performance is most favorable when the shape of the open electrode at the bottom is a five-vertex electrode, enabling a concentration enhancement factor of 55 times for a latex particle solution and 11 times for E. coli. The experimental results also demonstrate that the concentration phenomenon in this study is not induced by non-specific adsorption and can be repeated multiple times.


Assuntos
Eletro-Osmose/instrumentação , Eletroforese/instrumentação , Eletrodos , Desenho de Equipamento , Escherichia coli/isolamento & purificação , Microesferas , Modelos Químicos
8.
Electrophoresis ; 39(17): 2181-2187, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29896779

RESUMO

A nanoporous poly-(styrene sulfonate) (poly-SS) membrane was developed for fast and selective ion transport in a microfluidic chip. The poly-SS membrane can be photopolymerized in-situ at arbitrary location of a microchannel, enabling integrated fluidics design in the microfluidic chip. The membrane is characterized by a low hydraulic resistance and a high surface charge to maximize the electroosmotic flow and charge selectivity. The membrane characteristics were investigated by charge-selective electropreconcentration method. Experimental results show membranes with various percentages of poly-SS are able to concentrate anions (fluorescein and TRITC-labeled BSA). The anion-selective electropreconcentration process is stable and 26-times faster than previously reported poly-AMPS (2-acrylamido-2-methyl-1-propanesulfonic acid) based system. The electropreconcentration was also demonstrated to depend on the sample valency and buffer concentration.


Assuntos
Eletro-Osmose/métodos , Membranas Artificiais , Técnicas Analíticas Microfluídicas/métodos , Nanoporos , Ânions/análise , Ânions/química , Ânions/isolamento & purificação , Eletro-Osmose/instrumentação , Desenho de Equipamento , Técnicas Analíticas Microfluídicas/instrumentação , Poliestirenos/química
9.
Lab Chip ; 18(6): 861-868, 2018 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-29459920

RESUMO

We present a novel microfluidic paper-based analytical device (µPAD) which utilizes the native high electroosmotic flow (EOF) in nitrocellulose to achieve stationary isotachophoresis (ITP) focusing. This approach decouples sample accumulation from the length of the channel, resulting in significant focusing over short channel lengths. We provide a brief theory for EOF-balanced ITP focusing under continuous injection from a depleting reservoir and present the design of a short (7 mm) paper-based microfluidic channel, which allows a 200 µL sample to be processed in approximately 6 min, resulting in a 20 000-fold increase in concentration - a full order of magnitude improvement compared to previous paper-based ITP devices. We show the stability of the assay over longer (40 min) durations of time, and using Morpholino probes, we present the applicability of the device for amplification-free detection of nucleic acids, with a limit-of-detection (LoD) of 5 pM in 10 min. Finally, we utilize the small footprint of the channel and show a multiplexed platform in which 12 assays operate in parallel in a 24-well plate format.


Assuntos
DNA/análise , Eletro-Osmose , Isotacoforese , Técnicas Analíticas Microfluídicas , Papel , Colódio/química , Eletro-Osmose/instrumentação , Isotacoforese/instrumentação , Técnicas Analíticas Microfluídicas/instrumentação
10.
Bioelectrochemistry ; 120: 76-82, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29182911

RESUMO

Employing electric phenomena for the spatial manipulation of bioparticles from whole cells down to dissolved molecules has become a useful tool in biotechnology and analytics. AC electrokinetic effects like dielectrophoresis and AC electroosmosis are increasingly used to concentrate, separate and immobilize DNA and proteins. With the advance of photolithographical micro- and nanofabrication methods, novel or improved bioanalytical applications benefit from concentrating analytes, signal enhancement and locally controlled immobilization by AC electrokinetic effects. In this review of AC electrokinetics of proteins, the respective studies are classified according to their different electrode geometries: individual electrode pairs, interdigitated electrodes, quadrupole electrodes, and 3D configurations of electrode arrays. Known advantages and disadvantages of each layout are discussed.


Assuntos
Eletro-Osmose/instrumentação , Eletroforese/instrumentação , Proteínas/análise , Animais , Eletricidade , Eletrodos , Eletro-Osmose/métodos , Eletroforese/métodos , Desenho de Equipamento , Humanos
11.
Electrophoresis ; 39(5-6): 887-896, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29068080

RESUMO

Insulator-based dielectrophoresis (iDEP) exploits in-channel hurdles and posts etc. to create electric field gradients for various particle manipulations. However, the presence of such insulating structures also amplifies the Joule heating in the fluid around themselves, leading to both temperature gradients and electrothermal flow. These Joule heating effects have been previously demonstrated to weaken the dielectrophoretic focusing and trapping of microscale and nanoscale particles. We find that the electrothermal flow vortices are able to entrain submicron particles for a localized enrichment near the insulating tips of a ratchet microchannel. This increase in particle concentration is reasonably predicted by a full-scale numerical simulation of the mass transport along with the coupled charge, heat and fluid transport. Our model also predicts the electric current and flow pattern in the fluid with a good agreement with the experimental observations.


Assuntos
Eletro-Osmose/instrumentação , Eletroforese/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Microesferas , Dimetilpolisiloxanos/química , Eletricidade , Campos Eletromagnéticos , Desenho de Equipamento/instrumentação , Concentração de Íons de Hidrogênio , Modelos Teóricos , Propriedades de Superfície , Temperatura , Termodinâmica
12.
Electrophoresis ; 39(4): 597-607, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29115688

RESUMO

We report herein a novel microfluidic particle concentrator that utilizes constriction microchannels to enhance the flow-focusing performance of induced-charge electroosmosis (ICEO), where viscous hemi-spherical oil droplets are embedded within the mainchannel to form deformable converging-diverging constriction structures. The constriction region between symmetric oil droplets partially coated on the electrode strips can improve the focusing performance by inducing a granular wake flow area at the diverging channel, which makes almost all of the scattered sample particles trapped within a narrow stream on the floating electrode. Another asymmetric droplet pair arranged near the outlets can further direct the trajectory of focused particle stream to one specified outlet port depending on the symmetry breaking in the shape of opposing phase interfaces. By fully exploiting rectification properties of induced-charge electrokinetic phenomena at immiscible water/oil interfaces of tunable geometry, the expected function of continuous and switchable flow-focusing is demonstrated by preconcentrating both inorganic silica particles and biological yeast cells. Physical mechanisms responsible for particle focusing and locus deflection in the droplet-assisted concentrentor are analyzed in detail, and simulation results are in good accordance with experimental observations. Our work provides new routes to construct flexible electrokinetic framework for preprocessing on-chip biological samples before performing subsequent analysis.


Assuntos
Eletro-Osmose/instrumentação , Técnicas Analíticas Microfluídicas/instrumentação , Desenho de Equipamento , Dióxido de Silício , Leveduras/citologia
13.
Electrophoresis ; 39(5-6): 878-886, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29288585

RESUMO

This paper presents the use of DC-biased AC electric field for enhancing cell trapping throughput in an insulator-based dielectrophoretic (iDEP) fluidic device with densely packed silica beads. Cell suspension is carried through the iDEP device by a pressure-driven flow. Under an applied DC-biased AC electric field, DEP trapping force is produced as a result of non-uniform electric field induced by the gap of electrically insulating silica beads packed between two mesh electrodes that allow both fluid and cells to pass through. While the AC component is mainly to control the magnitude of DEP trapping force, the DC component generates local electroosmotic (EO) flow in the cavity between the beads and the EO flow can be set to move along or against the main pressure-driven flow. Our experimental and simulation results show that desirable trapping is achieved when the EO flow direction is along (not against) the main flow direction. Using our proposed DC-biased AC field, the device can enhance the trapping throughput (in terms of the flowrate of cell suspension) up to five times while yielding almost the same cell capture rates as compared to the pure AC field case. Additionally, the device was demonstrated to selectively trap dead yeast cells from a mixture of flowing live and dead yeast cells.


Assuntos
Eletro-Osmose/instrumentação , Eletroforese/instrumentação , Ensaios de Triagem em Larga Escala/instrumentação , Saccharomyces cerevisiae/isolamento & purificação , Dióxido de Silício/química , Adesão Celular , Eletricidade , Eletrodos , Campos Eletromagnéticos , Desenho de Equipamento/instrumentação , Modelos Teóricos , Pressão , Propriedades de Superfície
14.
Anal Chem ; 89(20): 10806-10812, 2017 10 17.
Artigo em Inglês | MEDLINE | ID: mdl-28944662

RESUMO

Single-cell analysis has attracted increasing attention because of cell heterogeneities. Various strategies have been developed for analyzing single cells, but most of these analytical processes kill the cells. Tools that can qualitatively and quantitatively measure the cellular contents without killing the cell are highly demanding because they enable us to conduct single-cell time-course studies (e.g., to examine how a cell responds to a therapy before, during, and after a treatment). Here we develop a femto-liter (fL) pipet to serve this purpose. To ensure that we can accurately and precisely pipet fL solutions, we fill all conduits with liquid and use an electroosmotic pump (EOP) as the driving force to facilitate withdrawal of cellular contents from single cells. We tentatively term this device an EOP-driven pipette or EDP. We characterize the EDP for accurately and precisely withdrawing solution from ∼250 fL to 80 nL; a volume range that covers the applications for most types of cells. To demonstrate the feasibility of utilizing the EDP for a single-cell time-course study, we utilize the EDP to take the cellular contents out at different times during the course of a zebrafish embryo development for cholesterol measurements. More than 50% of the embryos survive after each pipetting and analysis step, and this number will increase considerably as we improve our cell manipulation skills and reduce the pipet-tip diameter. We expect this EDP to become an effective tool for single-cell time-course studies.


Assuntos
Colesterol/análise , Eletro-Osmose/métodos , Embrião não Mamífero/metabolismo , Animais , Eletro-Osmose/instrumentação , Análise de Célula Única , Peixe-Zebra
15.
Anal Chem ; 89(18): 10022-10028, 2017 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-28812359

RESUMO

Continuous-flow electrophoresis of macromolecules is demonstrated using an integrated capillary-well sieve arranged into a two-dimensional anisotropic array on silicon. The periodic array features thousands of entropic barriers, each resulting from an abrupt interface between a 2 µm deep well (channel) and a 70 nm capillary. These entropic barriers owing to two-dimensional confinement within the capillaries are vastly steep in relation to those arising from slits featuring one-dimensional confinement. Thus, the sieving mechanisms can sustain relatively large electric field strengths over a relatively small array area. The sieve rapidly sorts anionic macromolecules, including DNA chains and proteins in native or denatured states, into distinct trajectories according to size or charge under electric field vectors orthogonally applied. The baseline separation is achieved in less than 1 min within a horizontal migration length of ∼1.5 mm. The capillaries are self-enclosed conduits in cylindrical profile featuring a uniform diameter and realized through an approach that avoids advanced patterning techniques. The approach exploits a thermal reflow of a layer of doped glass for shape transformation into cylindrical capillaries and for controllably shrinking the capillary diameter. Lastly, atomic layer deposition of alumina is introduced for the first time to fine-tune the capillary diameter as well as to neutralize the surface charge, thereby suppressing undesired electroosmotic flows.


Assuntos
Toxina da Cólera/química , DNA Viral/química , Eletro-Osmose , Anisotropia , Bacteriófagos , Eletro-Osmose/instrumentação , Eletroforese Capilar/instrumentação , Tamanho da Partícula , Silício/química , Propriedades de Superfície
16.
PLoS One ; 12(8): e0180974, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28771496

RESUMO

China is a country with vast territory, but economic development and population growth have reduced the usable land resources in recent years. Therefore, reclamation by pumping and filling is carried out in eastern coastal regions of China in order to meet the needs of urbanization. However, large areas of reclaimed land need rapid drainage consolidation treatment. Based on past researches on how to improve the treatment efficiency of soft clay using vacuum preloading combined with electro-osmosis, a two-dimensional drainage plane model was proposed according to the Terzaghi and Esrig consolidation theory. However, the analytical solution using two-dimensional plane model was never involved. Current analytical solutions can't have a thorough theoretical analysis of practical engineering and give relevant guidance. Considering the smearing effect and the rectangle arrangement pattern, an analytical solution is derived to describe the behavior of pore-water and the consolidation process by using EKG (electro-kinetic geo synthetics) materials. The functions of EKG materials include drainage, electric conduction and corrosion resistance. Comparison with test results is carried out to verify the analytical solution. It is found that the measured value is larger than the applied vacuum degree because of the stacking effect of the vacuum preloading and electro-osmosis. The trends of the mean measured value and the mean analytical value processes are comparable. Therefore, the consolidation model can accurately assess the change in pore-water pressure and the consolidation process during vacuum preloading combined with electro-osmosis.


Assuntos
Eletrocardiografia/instrumentação , Eletro-Osmose/instrumentação , Modelos Teóricos , Vácuo , Eletrodos
17.
Anal Chem ; 89(17): 9201-9208, 2017 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-28832110

RESUMO

MicroRNAs (miRs) are small noncoding RNAs that play a critical role in gene regulation. Recently, traces of cancer-related miRs have been identified in body fluids, which make them remarkable noninvasive biomarkers. In this study, a new nanopore-based detection scheme utilizing a borosilicate micropipette and an assay of complementary γ-peptide nucleic acid (γ-PNA) probes conjugated to polystyrene beads have been reported for the detection of miR-204 and miR-210 related to the clear cell Renal Cell Carcinoma (ccRCC). Electroosmotic flow (EOF) is induced as the driving force to transport PNA-beads harboring target miRs to the tip of the pore (sensing zone), which results in pore blockades with unique and easily distinguishable serrated shape electrical signals. The concentration detection limit is investigated to be 1 and 10 fM for miR-204 and miR-210, respectively. The EOF transport mechanism enables highly sensitive detection of molecules with low surface charge density with 97.6% detection accuracy compared to the conventional electrophoretically driven methods. Furthermore, resistive-pulse experiments are conducted to study the correlation of the particles' surface charge density with their translocation time and verify the detection principle.


Assuntos
Carcinoma de Células Renais/metabolismo , Eletro-Osmose/instrumentação , Dispositivos Lab-On-A-Chip , MicroRNAs/metabolismo , Nanoporos , Biomarcadores Tumorais/genética , Eletro-Osmose/métodos , Regulação Neoplásica da Expressão Gênica , Humanos , Neoplasias Renais/patologia , MicroRNAs/genética
18.
Environ Res ; 157: 30-36, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28511078

RESUMO

The feasibility of pressure-driven electro-dewatering (EDW) on sludge samples taken after different biological processes, stabilisation methods or mechanical dewatering techniques was assessed. First, the influence of potential values on EDW of anaerobically and aerobically stabilised, mechanically dewatered, sludge samples was investigated. Preliminary tests carried out by applying a constant potential (10, 15 and 20V) in a lab-scale device confirmed the possibility to reach a dry solid (DS) content of up to 42.9%, which corresponds to an increase of 15% of the dry content in dewatered sludge without the application of the electrical field. Dewatering increased with the applied potential but at the expense of a higher energy consumption. A potential equal to 15V was chosen as the best compromise for EDW performance, in terms of DS content and energy consumption. Then, the influence of the mechanical dewatering was studied on aerobically stabilised sludge samples with a lower initial DS content: the higher initial water content led to a lower final DS content but with a considerable reduction of energy consumption. Finally, the biological process, studied by comparing sludge samples from conventional activated sludge and membrane bioreactor processes, didn't evidence any influence on EDW. Experimental results shown that DS obtained after mechanical dewatering, volatile solids and conductivity are the main factors influencing EDW. Anaerobically digested sludge reached the highest DS content, thanks to lower organic fraction.


Assuntos
Eletro-Osmose/métodos , Esgotos/análise , Eliminação de Resíduos Líquidos/métodos , Eletro-Osmose/instrumentação
19.
Nano Lett ; 17(4): 2374-2380, 2017 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-28296413

RESUMO

Label-free, nanoparticle-based plasmonic optical biosensing, combined with device miniaturization and microarray integration, has emerged as a promising approach for rapid, multiplexed biomolecular analysis. However, limited sensitivity prevents the wide use of such integrated label-free nanoplasmonic biosensors in clinical and life science applications where low-abundance biomolecule detection is needed. Here, we present a nanoplasmofluidic device integrated with microelectrodes for rapid, label-free analysis of a low-abundance cell signaling protein, detected by AC electroosmosis-enhanced localized surface plasmon resonance (ACE-LSPR) biofunctional nanoparticle imaging. The ACE-LSPR device is constructed using both bottom-up and top-down sensor fabrication methods, allowing the seamless integration of antibody-conjugated gold nanorod (AuNR) biosensor arrays with microelectrodes on the same microfluidic platform. Applying an AC voltage to microelectrodes while scanning the scattering light intensity variation of the AuNR biosensors results in significantly enhanced biosensing performance. The AC electroosmosis (ACEO) based enhancement of the biosensor performance enables rapid (5-15 min) quantification of IL-1ß, a pro-inflammatory cytokine biomarker, with a sensitivity down to 158.5 fg/mL (9.1 fM) for spiked samples in PBS and 1 pg/mL (58 fM) for diluted human serum. Together with the optimized detection sensitivity and speed, our study presents the first critical step toward the application of nanoplasmonic biosensing technology to immune status monitoring guided by low-abundance cytokine measurement.


Assuntos
Técnicas Biossensoriais/métodos , Citocinas/sangue , Eletro-Osmose/instrumentação , Dispositivos Lab-On-A-Chip , Biomarcadores/sangue , Técnicas Biossensoriais/instrumentação , Técnicas Eletroquímicas/instrumentação , Eletrodos , Ouro/química , Humanos , Limite de Detecção , Nanotecnologia , Nanotubos/química , Imagem Óptica/métodos , Tamanho da Partícula , Ressonância de Plasmônio de Superfície
20.
Electrophoresis ; 38(20): 2554-2560, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28314051

RESUMO

Fluid flow profiles in free liquid films stabilised by anionic and cationic surfactants under an external electric field were investigated. Depthwise velocity fields were measured at the mid region of the free liquid film by confocal micron-resolution particle image velocimetry and corresponding numerical simulations were performed using Finite Element Method to model the system. Depthwise change in velocity profiles was observed with electroosmotic flow dominating in the vicinity of the gas-liquid and solid-liquid interfaces while backpressure drives fluid in the opposite direction at the core of the film. It was also found that the direction of the flow at various sections of the films depends on the type of surfactant used, but flow features remained the same. Numerical simulations predicted the flow profiles with reasonable accuracy; however, asymmetry of the actual film geometry caused deviations at the top half of the computational domain. Overall, electroosmotic flow profiles within a free liquid film are similar to that of the closed-end solid microchannel. However, the flow direction and features of the velocity profiles can be changed by selecting various types of surfactants. The free liquid films thickness was selected to match dimensions of foam Plateau border. Hence, these findings will be useful in developing a separation system based on foam electrokinetics.


Assuntos
Simulação por Computador , Eletro-Osmose/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Eletricidade , Eletroforese , Reologia , Tensoativos/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA