Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
ACS Omega ; 4(7): 12938-12947, 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31460420

RESUMO

Flow-through optical chromatography (FT-OC), an advanced mode of optical chromatography, achieved baseline separation of a mixture of silica microparticles (SiO2, 1.00 and 2.50 µm) and a mixture of polystyrene microparticles (PS, 1.00, 2.00, and 3.00 µm) based on particle size. Comparisons made between experimentally determined velocities for the microparticles and theoretically derived velocities from Mie theory and Stokes' law validated the data collection setup and the data analysis for FT-OC. A population shift in live macrophages (cell line IC-21, ATCC TIB-186) responding to environmental stimuli was sensitively detected by FT-OC. The average velocity of macrophages stressed by nutritional deprivation was decreased considerably together with a small but statistically significant increase in cell size. Mie scattering calculations demonstrated that the small increase in cell size of macrophages stressed by nutritional deprivation was not entirely responsible for this decrease. Confocal fluorescence microscopy and atomic force microscopy (AFM) studies revealed morphological changes of macrophages induced by nutritional deprivation, and these changes were more likely responsible for the decrease in average velocity detected by FT-OC. Confocal Raman microspectroscopy was used to shed light upon biochemical transformations of macrophages suffering from nutritional deprivation.

2.
Anal Chem ; 89(19): 10296-10302, 2017 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-28876903

RESUMO

Understanding the interaction between macrophage cells and Bacillus anthracis spores is of significant importance with respect to both anthrax disease progression, spore detection for biodefense, as well as understanding cell clearance in general. While most detection systems rely on specific molecules, such as nucleic acids or proteins and fluorescent labels to identify the target(s) of interest, label-free methods probe changes in intrinsic properties, such as size, refractive index, and morphology, for correlation with a particular biological event. Optical chromatography is a label free technique that uses the balance between optical and fluidic drag forces within a microfluidic channel to determine the optical force on cells or particles. Here we show an increase in the optical force experienced by RAW264.7 macrophage cells upon the uptake of both microparticles and B. anthracis Sterne 34F2 spores. In the case of spores, the exposure was detected in as little as 1 h without the use of antibodies or fluorescent labels of any kind. An increase in the optical force was also seen in macrophage cells treated with cytochalasin D, both with and without a subsequent exposure to spores, indicating that a portion of the increase in the optical force arises independent of phagocytosis. These results demonstrate the capability of optical chromatography to detect subtle biological differences in a rapid and sensitive manner and suggest future potential in a range of applications, including the detection of biological threat agents for biodefense and pathogens for the prevention of sepsis and other diseases.


Assuntos
Bacillus anthracis/fisiologia , Óptica e Fotônica/métodos , Esporos Bacterianos/metabolismo , Animais , Citocalasina D/metabolismo , Dispositivos Lab-On-A-Chip , Lasers , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Macrófagos/citologia , Macrófagos/metabolismo , Macrófagos/microbiologia , Camundongos , Microscopia Confocal , Fagocitose , Células RAW 264.7 , Esporos Bacterianos/imunologia
3.
Analyst ; 139(6): 1472-81, 2014 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-24492491

RESUMO

The rapid and robust identification of viral infections has broad implications for a number of fields, including medicine, biotechnology and biodefense. Most detection systems rely on specific molecules, such as nucleic acids or proteins, to identify the target(s) of interest. These molecules afford great specificity, but are often expensive, labor-intensive, labile and limited in scope. Label free detection methods seek to overcome these limitations by instead using detection methods that rely on intrinsic properties as a basis for identifying and separating species of interest and thus do not rely on specific prior knowledge of the target. Optical chromatography, one such technique, uses the balance between optical and fluidic drag forces within a microfluidic channel to determine the optical force on cells or particles. Here we present the application of individual optical force measurements as a means of investigating pseudorabies virus infection in Vero cells. Optical force differences are seen between cells from uninfected and infected populations at a multiplicity of infection as low as 0.001 and as soon as 2 hours post infection, demonstrating the potential of this technique as a means of detecting viral infection. Through the application of a pattern recognition neural network, individual cell size data are combined with optical force as a means of classifying cell populations. Potential applications include the early detection of bloodborne pathogens for the prevention of sepsis and other diseases as well as the detection of biological threat agents.


Assuntos
Herpesvirus Suídeo 1/isolamento & purificação , Pseudorraiva/diagnóstico , Células Vero/virologia , Animais , Técnicas Biossensoriais , Chlorocebus aethiops , Lasers , Técnicas Analíticas Microfluídicas , Microscopia , Imagem Óptica
4.
Anal Chem ; 85(18): 8647-53, 2013 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-23964641

RESUMO

Results are reported from a combined optical force and electrokinetic microfluidic device that separates individual particulates from molecular components in a mixed sample stream. A pico-Newton optical force was applied to an orthogonal electroosmotic flow carrying a hydrodynamically pinched, mixed sample, resulting in the separation of the various particles from the sample stream. Different combinations of polystyrene, PMMA, and silica particles with a commercially available dye were utilized to test the different separation modes available, from purely optical force to combined optical and electrophoretic forces. The impact of various particle properties on particle separation and separation efficiency were explored, including size (2, 6, 10 µm), refractive index, and electrophoretic mobility. Particle addressability was achieved by moving particles to different outlets on the basis of particle size, refractive index, and electrophoretic differences. Separations of 6 and 10 µm polystyrene particles led to only 3% particle contamination in the original sample stream and interparticle type enrichment levels >80%. The unique addressability of three different particle materials (polystyrene, PMMA, and silica) of the same size (2 µm) led to each being separated into a unique outlet without measurable contamination of the other particle types using optical force and electrophoretic mobility. In addition to particle separation, the device was able to minimize dye diffusion, leading to >95% dye recovery. This combined platform would have applications for noninvasive sample preparation of mixed molecular/particulate systems for mating with traditional analytics as well as efficient removal of harmful, degrading components from complex mixtures.

5.
Electrophoresis ; 34(8): 1175-81, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23404174

RESUMO

Presented here are the results from numerical simulations applying optical forces orthogonally to electroosmotically induced flow containing both molecular species and particles. Simulations were conducted using COMSOL v4.2a Multiphysics® software including the particle tracking module. The study addresses the application of optical forces to selectively remove particulates from a mixed sample stream that also includes molecular species in a pinched flow microfluidic device. This study explores the optimization of microfluidic cell geometry, magnitude of the applied direct current electric field, EOF rate, diffusion, and magnitude of the applied optical forces. The optimized equilibrium of these various contributing factors aids in the development of experimental conditions and geometry for future experimentation as well as directing experimental expectations, such as diffusional losses, separation resolution, and percent yield. The result of this work generated an optimized geometry with flow conditions leading to negligible diffusional losses of the molecular species while also being able to produce particle removal at near 100% levels. An analytical device, such as the one described herein with the capability to separate particulate and molecular species in a continuous, high-throughput fashion would be valuable by minimizing sample preparation and integrating gross sample collection seamlessly into traditional analytical detection methods.


Assuntos
Eletro-Osmose/instrumentação , Técnicas Analíticas Microfluídicas/instrumentação , Simulação por Computador , Microesferas , Tamanho da Partícula , Software
6.
Anal Chim Acta ; 718: 11-24, 2012 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-22305893

RESUMO

On-line sample preconcentration is an essential tool in the development of microfluidic-based separation platforms. In order to become more competitive with traditional separation techniques, the community must continue to develop newer and more novel methods to improve detection limits, remove unwanted sample matrix components that disrupt separation performance, and enrich/purify analytes for other chip-based actions. Our goal in this review is to familiarize the reader with many of the options available for on-chip concentration enhancement with a focus on those manuscripts that, in our assessment, best describe the fundamental principles that govern those enhancements. Sections discussing both electrophoretic and nonelectrophoretic modes of preconcentration are included with a focus on device design and mechanisms of preconcentration. This review is not meant to be a comprehensive collection of every available example, but our hope is that by learning how on-line sample concentration techniques are being applied today, the reader will be inspired to apply these techniques to further enhance their own programs.

7.
Lab Chip ; 12(6): 1128-34, 2012 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-22315144

RESUMO

A unique microfluidic system is developed which enables the interrogation of a single particle by using multiple force balances from a combination of optical force, hydrodynamic drag force, and electrophoretic force. Two types of polystyrene (PS) particles with almost identical size and refractive index (plain polystyrene (PS) particle - mean diameter: 2.06 µm, refractive index: 1.59; carboxylated polystyrene (PS-COOH) particles - mean diameter: 2.07 µm, refractive index: 1.60), which could not be distinguished by optical chromatography, reveal different electrokinetic behaviors resulting from the difference in their surface charge densities. The PS-COOH particles, despite their higher surface charge density when compared to the PS particles, experience a lower electrophoretic force, regardless of ionic strength. This phenomenon can be understood when the more prominent polarization of the counter ion cloud surrounding the PS-COOH particles is considered. The surface roughness of the carboxylated particles also plays an important role in the observed electrokinetic behavior.

8.
Anal Chem ; 83(14): 5666-72, 2011 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-21634802

RESUMO

There is a compelling need to develop systems capable of processing blood and other particle streams for detection of pathogens that are sensitive, selective, automated, and cost/size effective. Our research seeks to develop laser-based separations that do not rely on prior knowledge, antibodies, or fluorescent molecules for pathogen detection. Rather, we aim to harness inherent differences in optical pressure, which arise from variations in particle size, shape, refractive index, or morphology, as a means of separating and characterizing particles. Our method for measuring optical pressure involves focusing a laser into a fluid flowing opposite to the direction of laser propagation. As microscopic particles in the flow path encounter the beam, they are trapped axially along the beam and are pushed upstream from the laser focal point to rest at a point where the optical and fluid forces on the particle balance. On the basis of the flow rate at which this balance occurs, the optical pressure felt by the particle can be calculated. As a first step in the development of a label-free device for processing blood, a system has been developed to measure optical pressure differences between the components of human blood, including erythrocytes, monocytes, granulocytes, and lymphocytes. Force differentials have been measured between various components, indicating the potential for laser-based separation of blood components based upon differences in optical pressure. Potential future applications include the early detection of blood-borne pathogens for the prevention of sepsis and other diseases as well as the detection of biological threat agents.


Assuntos
Células Sanguíneas/citologia , Lasers , Óptica e Fotônica/instrumentação , Linhagem Celular Tumoral , Tamanho Celular , Desenho de Equipamento , Humanos
9.
Anal Chim Acta ; 670(1-2): 78-83, 2010 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-20685420

RESUMO

In this work, microscopic particles in a fluid flow are manipulated using forces generated by a high power laser beam. The resulting manipulations on the particles are imaged using a microscope lens connected to a CCD camera. Differential forces on particles of varying physical and chemical composition have been measured. The goal is to measure the optical forces on a diverse range of particles and catalog the associated chemical and physical differences to understand which properties and mechanisms result in the largest force differentials. Using these measurements our aim is to better understand differences between similar microspheres in terms of size, morphology, or chemical composition. Particles of the same size, but different composition show large variations in optical pressure forces and are easily discernable in the present analytical system. In addition, we have demonstrated the ability to differentiate a 70 nm size difference between two NIST precision size standard polystyrene microspheres, corresponding to a 2.0 pN difference in optical force. Lastly, the instrument was used to measure differences between biological samples of similar size, demonstrating the ability to make precise analytical measurements on microorganism samples.


Assuntos
Bacillus anthracis/química , Bacillus thuringiensis/química , Geobacter/química , Óptica e Fotônica , Tamanho da Partícula , Espectrometria de Fluorescência
10.
Lab Chip ; 10(13): 1729-31, 2010 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-20376381

RESUMO

We present the construction and operation of a microfluidic nozzle created using several standard fluidic parts available commercially. By elegantly combining several pieces from a standard assembly, a capillary and a few other standard parts, we were able to develop a novel device. Using this device, precise axisymmetric flow focusing of particles was achieved and observed at the exit of the nozzle and within a connected microfluidic device several centimetres away. Sheath and core flow rates were varied to show influence and control over the width of the focused particles.


Assuntos
Análise de Injeção de Fluxo/instrumentação , Técnicas Analíticas Microfluídicas/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento
11.
Opt Express ; 17(3): 2024-32, 2009 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-19189033

RESUMO

Optical chromatography achieves microscale optical manipulation through the balance of optical and hydrodynamic forces on micron sized particles entrained in microfluidic flow traveling counter to the propagation of a mildly focused laser beam. The optical pressure force on a particle is specific to each particle's size, shape and refractive index. So far, these properties have been exploited in our lab to concentrate, purify and separate injected samples. But as this method advances into more complex optofluidic systems, a need to better predict behavior is necessary. Here, we present the development and experimental verification of a robust technique to simulate particle trajectories in our optical chromatographic device. We also show how this new tool can be used to gather better qualitative and quantitative understanding in a two component particle separation.

12.
Biomicrofluidics ; 3(4): 44106, 2009 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-20216968

RESUMO

Optical chromatography involves the elegant combination of opposing optical and fluid drag forces on colloidal samples within microfluidic environments to both measure analytical differences and fractionate injected samples. Particles that encounter the focused laser beam are trapped axially along the beam and are pushed upstream from the laser focal point to rest at a point where the optical and fluid forces on the particle balance. In our recent devices particles are pushed into a region of lower microfluidic flow, where they can be retained and fractionated. Because optical and fluid forces on a particle are sensitive to differences in the physical and chemical properties of a sample, separations are possible. An optical chromatography beam focused to completely fill a fluid channel is operated as an optically tunable filter for the separation of inorganic, polymeric, and biological particle samples. We demonstrate this technique coupled with an advanced microfluidic platform and show how it can be used as an effective method to fractionate particles from an injected multicomponent sample. Our advanced three-stage microfluidic design accommodates three lasers simultaneously to effectively create a sequential cascade optical chromatographic separation system.

13.
Anal Chem ; 80(21): 8287-92, 2008 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-18837518

RESUMO

An electroosmotic flow (EOF)-based pump, integrated with a sol-gel stationary phase located in the electric field-free region of a microchip, enabled the separation of six nitroaromatic and nitramine explosives and their degradation products via liquid chromatography (LC). The integrated pump and LC system were fabricated within a single quartz substrate. The pump region consisted of a straight channel (3.0 cm x 230 microm x 100 microm) packed with 5-microm porous silica beads. The sol-gel stationary phase was derived from a precursor mixture of methyltrimethoxy- and phenethyltrimethoxysilanes and was synthesized in the downstream, field-free region of the microchip, resulting in a stationary-phase monolith with dimensions of 2.6 cm x 230 microm x 100 microm. Fluid dynamic design considerations are discussed, especially as they relate to integrating the EOF pump with the LC system. Pump and separation performance, as characterized by flow rate measurements, injection, elution, separation, and detection, point to a viable analytical chemistry platform that encompasses all of the benefits expected of portable, laboratory-on-chip systems, including reduced sample requirements and small packaging.

14.
Opt Express ; 16(23): 18782-9, 2008 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-19581966

RESUMO

Optical chromatography, used for particle separation, involves loosely focusing a laser into a fluid flowing opposite the direction of laser propagation. When microscopic particles in the flow path encounter this beam they are trapped axially along the beam and are pushed upstream from the laser focal point to rest at a point where the optical and fluid forces on the particle balance. Because optical and fluid forces are sensitive to differences in the physical and chemical properties of a particle, separations are possible. An optical chromatography beam which completely fills a fluid channel can operate as an optically tunable filter for the preparative separation of polymeric/colloidal and biological samples. We show how the technique can be used to separate injected samples containing large numbers of colloids. The power of optical chromatographic separations is illustrated through combination with epi-fluorescence microscopy and sample purification for real-time polymerase chain reaction (RT-PCR) detection of Bacillus anthracis spores.


Assuntos
Lasers , Microscopia de Fluorescência/instrumentação , Dispositivos Ópticos , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
15.
Opt Express ; 15(5): 2724-31, 2007 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-19532509

RESUMO

Optical chromatography is a technique for the separation of particles that capitalizes on the balance between optic and fluidic forces. When microscopic particles in a fluid flow encounter a laser beam propagating in the opposite direction, they are trapped axially along the beam. They are then optically pushed upstream from the laser focal point to rest at a point where the optic and fluidic forces on the particle balance. Because optical and fluid forces are sensitive to differences in the physical and chemical properties of a particle, both coarse and fine separations are possible. We describe how an optical chromatography beam directed into a tailored flow environment, has been adapted to operate as an optical filter for the concentration / bioenrichment of colloidal and biological samples. In this work, the demonstrated ability to concentrate spores of the biowarfare agent, Bacillus anthracis, may have significant impact in the biodefense arena. Application of these techniques and further design of fluidic and optical environments will allow for more specific identification, concentration and separation of many more microscopic particle and biological suspensions.

16.
Anal Chem ; 78(24): 8412-20, 2006 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-17165834

RESUMO

A microchip-based, displacement immunoassay for the sensitive laser-induced fluorescence detection of staphylococcal enterotoxin B is presented. The glass microchip device consists of a microchannel that contains a double weir structure for supporting antibody-functionalized microbeads. After a 30-min sample preparation step, the displacement assay was performed without user intervention and produced quantitative results in an additional 20 min. Linear detection responses were observed over 6 orders of magnitude and provided detection limits down to 1 fM (28.5 fg/mL). The surprisingly low detection limits are hypothesized to arise from field-based enrichment analogous to field-amplified stacking, chromatographic effects, and limited diffusion lengths in the microbead bed. The assay was challenged with bovine serum albumin, casein, and milk sample matrixes. This system has the potential to provide highly sensitive detection capabilities for target biomolecules.


Assuntos
Caseínas/análise , Enterotoxinas/análise , Imunoensaio , Procedimentos Analíticos em Microchip , Leite/química , Soroalbumina Bovina/análise , Animais , Bovinos , Enterotoxinas/toxicidade , Lasers , Leite/toxicidade , Sensibilidade e Especificidade , Espectrometria de Fluorescência , Fatores de Tempo
17.
Electrophoresis ; 27(21): 4295-302, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17022017

RESUMO

Microchip-based CEC of nitroaromatic and nitramine explosives with UV absorbance detection is described. The stationary phase was deposited in the microchip using the sol-gel process. Unique to this work, is the exclusive use of alkylated-trimethoxysilane precursors in the gel solution. Using alkylated precursors allows for the synthesis of a hydrophobic stationary phase in a single step. Three sol-gel formulations of increasing hydrophobicity and suitable for the separation of explosives are established from methyl- and ethyl-trimethoxysilane precursors. Increasing the alkyl-chain length improved the resolution significantly, allowing for the separation of up to seven analytes. Direct injection onto the head of the stationary phase for long injection times, results in sub-mg/L detection limits with little effect on separation efficiency.


Assuntos
Compostos de Anilina/análise , Eletrocromatografia Capilar/métodos , Eletroforese em Microchip/métodos , Substâncias Explosivas/análise , Hidrocarbonetos Aromáticos/análise , Nitrobenzenos/análise , Silanos/química , Géis , Sensibilidade e Especificidade , Espectrofotometria Ultravioleta
18.
Anal Chem ; 78(9): 3221-5, 2006 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-16643018

RESUMO

A significant difference between two closely related Bacillus spores has been discovered using optical chromatography. This difference can be harnessed for the separation of microscopic particles using opposing laser and fluid flow forces. Particles of different size, composition, and shape experience different optical and fluid forces and come to rest at unique equilibrium positions where the two forces balance. Separations in excess of 600 mum have been observed between Bacillus anthracis Sterne strain and its genetic relative, Bacillus thuringiensis. These findings open new possibilities for detection and characterization of the biological warfare agent, B. anthracis, the causative agent of anthrax, the deadly mammalian disease. The large optical separation between these species is surprising given their close genetic relationship but may be explained by differences in their shape and exosporium morphology, which may result in differences in fluid drag force. The observation of large differences due to less common variables indicates the complex nature of the force balance in optical chromatography, which may in the future be used to separate and characterize microbiological samples. In general, the discovery of such large differences between such closely related biological species suggests new possibilities for the separation and characterization of microorganisms using the full range of emerging techniques that employ radiation pressure (optical filtering, laser tweezers, optical chromatography, etc.).


Assuntos
Bacillus anthracis/química , Bacillus thuringiensis/química , Lasers , Óptica e Fotônica , Esporos Bacterianos/química , Microfluídica , Microscopia Eletrônica de Transmissão/métodos , Tamanho da Partícula , Sensibilidade e Especificidade , Esporos Bacterianos/isolamento & purificação , Fatores de Tempo
19.
Science ; 296(5574): 1841-4, 2002 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-12052952

RESUMO

By manipulating colloidal microspheres within customized channels, we have created micrometer-scale fluid pumps and particulate valves. We describe two positive-displacement designs, a gear and a peristaltic pump, both of which are about the size of a human red blood cell. Two colloidal valve designs are also demonstrated, one actuated and one passive, for the direction of cells or small particles. The use of colloids as both valves and pumps will allow device integration at a density far beyond what is currently achievable by other approaches and may provide a link between fluid manipulation at the macro- and nanoscale.


Assuntos
Coloides , Equipamentos e Provisões , Microesferas , Miniaturização , Nanotecnologia , Óptica e Fotônica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA