Government of the United States of America, As Represented by the Secretary of Commerce

Applied Research Associates, Inc.

Other

National Institute of Standards and Technology

Outback Bicycles, Inc.

The United States of America, As Represented by the Sectretary of Commerce, the National Institute of Standards and Technology

David Judson Ross

Laurie E Locascio

Alyssa Catharyn Henry

Timothy J Johnson

Wyatt N Vreeland

Michael J Tarlov

Karin M Balss

Peter B Howell, Jr

Elizabeth Strychalski

Emanuel A Waddell, Jr

Christopher Konek

Jason Kralj

Jonathan G Shackman

Susan L R Barker

Sam Forry

Aaron E Bard

Methods of detecting the presence of toxins in a sample using electrophoretic separations and of performing electrophoretic separation of complex samples are provided. The method of detecting the presence of toxins includes reacting a sample and a substrate with a signaling enzyme which converts the substrate to the product in a reaction medium, introducing a run buffer into a separation channel having an inlet end, selectively introducing at least one of the substrate and the product of the reaction medium into the inlet end of the separation channel, electrophoretically separating the substrate and the product, and determining the rate of conversion of the substrate to the product, wherein a change in the rate of conversion is indicative of the presence of toxins. The method of performing electrophoretic separations of complex samples having charged particulates and oppositely charged analytes comprising introducing a run buffer into a separation channel having an inlet end, selectively introducing the oppositely charged analytes in the complex sample into the separation channel, and electrophoretically separating the charged particulates and the oppositely charged analytes. Additionally, a device for varying with respect to time the bulk flow of a fluid in a separation channel of an electrophoretic device having a buffer reservoir in fluid contact with the separation channel is provided. The device includes a pressure sensor in fluid contact with a buffer reservoir, a high pressure reservoir in selective fluidic communication with the buffer reservoir, a low pressure reservoir in selective fluidic communication with the buffer reservoir and in fluidic communication with the high pressure reservoir, and a pumping device for pumping a gas from the low pressure reservoir to the high pressure reservoir.

Gradient elution moving boundary electrophoresis for use with complex samples and detection of toxins

Gradient elution isotachophoretic apparatus, and systems for performing gradient elution isotachophoresis to separate, purify, concentrate, quantify, and/or extract charged analytes from a sample. The isotachophoretic apparatus include an electrophoretic assembly, a sampling assembly connected to the electrophoretic assembly, and/or a support structure connected to the electrophoretic assembly and/or to the sampling assembly. The system includes an isotachophoretic apparatus, and a controller communicatively coupled to the isotachophoretic apparatus. The controller includes a storage medium and a processor for executing computer readable and executable instructions.

Gradient elution isotachophoretic apparatus for separating, purifying, concentrating, quantifying, and/or extracting charged analytes and methods thereof

A microfluidic apparatus and method for performing electrophoretic separation of compounds. The method comprises the steps of: a) providing a separation buffer; b) providing a sample solution in fluid contact with the separation buffer; c) applying an electric field to the separation buffer; and d) producing a variable bulk flow of the separation buffer in a direction substantially aligned with said electric field. Fluid contact between the separation buffer and the sample solution is made through a separation column having a length in the range of from approximately 0.01 mm to approximately 5 mm. By the foregoing, compounds can be sequentially detected and quantified.

Gradient elution electrophoresis and detectorless electrophoresis apparatus

Systems and methods for performing chromatography separations or analyses are disclosed. The methods are based upon an equilibrium gradient focusing mode in contrast to conventional transient migration-based modes. By matching the migration speed of one or more analyte(s) of interest to the wave speed of a thermal gradient induced to travel along a region in which chromatographic partitioning occurs, significant improvements in detection limits are achieved. In particular, a temperature gradient focusing strategy is described in which analyte(s) of interest are circulated around a continuous chromatography system in order to focus the analyte(s). Also described are various devices and systems that can be used in the methods described herein.

Recirculating temperature wave focusing chromatography

A method for performing electrophoretic separation of ionic compounds which involves varying a bulk fluid flow though a separation path into which ionic species are continuously introduced and separated. The method can also include the introduction of a leading electrolyte into the separation path to form an ionic interface with the sample and an optional terminating electrolyte to enrich ionic species for higher detection resolution.

Gradient elution electrophoresis

A method and device are provided for affinity gradient focusing for directing at least one analyte in a solution containing a pseudostationary phase and located in a channel such as a capillary or a microchannel. The method includes establishing a steady-state spatial gradient in a retention factor of the pseudostationary phase for the at least one analyte. The analyte is caused to be moved within the channel whereby the concentration of the at least one analyte changes at one or more positions along the gradient. The pseudostationary phase is charged and the analyte is either neutral or charged or alternatively, the pseudostationary phase is neutral and the analyte is charged. The device may include a fluid channel, a pseudostationary phase having a retention factor gradient, an electrical current source and a pump system for establishing the bulk flow in the solution in the channel.

Micellar gradient focusing

Disclosed is an apparatus and method for the mixing of two microfluidic channels wherein several wells are oriented diagonally across the width of a mixing channel. The device effectively mixes the confluent streams with electrokinetic flow, and to a lesser degree, with pressure driven flow. The device and method may be further adapted to split a pair of confluent streams into two or more streams of equal or non-equal concentrations of reactants. Further, under electrokinetic flow, the surfaces of said wells may be specially coated so that the differing electroosmotic mobility between the surfaces of the wells and the surfaces of the channel may increase the mixing efficiency. The device and method are applicable to the steady state mixing as well as the dynamic application of mixing a plug of reagent with a confluent stream.

Microfluidic flow manipulation device

A method and device are provided for concentrating and separating materials in fluids within a fluidic device having a fluid conduit such as a channel or capillary. The concentration is achieved by balancing the electrophoretic velocity of a material against the bulk flow of fluid in the presence of a temperature gradient. An additive is added to the fluid which interacts with the material and which modifies the normal electrophoretic mobility of the material. Using an appropriate fluid, the temperature gradient can generate a corresponding gradient in the electrophoretic velocity so that the electrophoretic and bulk velocities sum to zero at a unique position along the conduit and the material will be focused at that position. The method and device may be adapted for use with a variety of materials including fluorescent dyes, amino acids, proteins, DNA and to concentrate a dilute material.

Chiral temperature gradient focusing

A method is provided for observing mixing interactions and reactions of two materials in a fluid. The method in one form provides for concentrating by balancing electrophoretic velocities of a material against the bulk flow of fluid in the presence of a temperature gradient. Using an appropriate fluid, the temperature gradient can generate a corresponding gradient in the electrophoretic velocity of the material so that the electrophoretic and bulk velocities sum to zero at a unique position and the material will be focused at that position. A second material can then be introduced into the fluid and allowed to move through and interact with the focused band of the first material. Products of the interaction can then be detected as they are focused at a different position along the gradient. The method can be adapted to study the temperature dependence of the molecular interaction.

Mixing reactions by temperature gradient focusing

A method and device are provided for concentrating and separating ionic species in solution within a fluidic device having a fluid conduit such as a channel or capillary. The concentration is achieved by balancing the electrophoretic velocity of an analyte against the bulk flow of solution in the presence of a temperature gradient. Using an appropriate buffer, the temperature gradient can generate a corresponding gradient in the electrophoretic velocity so that the electrophoretic and bulk velocities sum to zero at a unique point and the analyte will be focused at that point. The method and device may be adapted for use with a variety of analytes including fluorescent dyes, amino acids, proteins, DNA and to concentrate a dilute analyte.

Fluidic temperature gradient focusing

A method is described for modifying performed channels fabricated in a variety of substrate materials including PMMA. The method involves exposing a portion of a fluid flow channel to light at a fluence and wavelength which modifies the surface charge of the substrate at the exposure site. The method can be used to modulate electroosmotic flow in channels or to immobilize chemical compounds or biological species in the fluid flow channels at the modified surfaces. The method can be used to fabricate or modify microfluidic systems

Surface charge modification within preformed polymer microchannels with multiple applications including modulating electroosmotic flow and creating microarrays

Method for microfluidic flow manipulation

A microchannel device is provided with a plastic substrate having a microchannel formed therein. Polyelectrolyte multilayers are disposed along selected surfaces of the microchannel. The polyelectrolyte layers comprise alternating net positively charged layers and net negatively charged layers. A microchannel lid has a surface facing the microchannel. In making the microchannel device, selected surfaces of the microchannel are alternatively exposed to solutions comprising positively charged polyelectrolytes and negatively charged polyelectrolytes to form the desired number of polyelectrolyte layers.

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Silver Spring, MD, United States of America

David Judson Ross