Chemistry: analytical and immunological testing – Involving an insoluble carrier for immobilizing immunochemicals
Reexamination Certificate
2000-04-18
2002-08-20
Ceperley, Mary E. (Department: 1641)
Chemistry: analytical and immunological testing
Involving an insoluble carrier for immobilizing immunochemicals
C436S043000, C436S055000, C436S169000, C436S178000, C436S512000, C436S524000, C436S527000, C436S528000, C436S536000, C436S541000, C435S006120, C435S007100, C435S007920, C435S174000, C435S176000, C435S177000, C435S287100, C435S287200, C435S287300, C435S287700, C435S288100, C435S288700, C422S050000, C422S051000, C422S051000, C422S051000, C422S063000, C422S068100, C422S083000, C422S088000, C422S105000, C422S119000, C422S255000, C422S256000, C422S261000, C422S283000, C422S919000, C422S947000
Reexamination Certificate
active
06436722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to devices and methods for performing assays to determine the presence or quantity of a specific analyte of interest in a fluid sample. Devices of this invention assay a measured amount of sample employing at least two separate and distinct flow paths which are initiated simultaneously with a single user activation step. These paths are timed for the sequential delivery of assay reagents to the reaction zone, followed by wash or substrate and wash reagents to that zone. These inventive devices and methods may be used for qualitative, semi-quantitative and quantitative determinations of one or multiple analytes in a single test format. They may be practiced with ELISA, sol particle and other assay formats, and are particularly suitable for simultaneous multiple analyte assays. These inventive devices and methods provide for the controlled, self delivery of reagents with no timed steps, and minimal user intervention, in most instances a single activation step.
2. Background
Many prior art assay devices and systems require the user to measure or control the amount of sample added to the device, for example, by dilution. Many prior art assays and systems also require the user to perform a timed sequence of steps and/or to make multiple physical interventions to the device in order to perform the assay.
Buechler et al., U.S. Pat. Nos. 5,458,852 and 5,885,527 (1995 and 1999, respectively), disclose diagnostic devices which do not use porous membranes. In assay methods using such devices, fluid flow is unidirectional and reaction and detection occur in distinct zones. Excess sample/conjugate mixture is used to wash the detection zone. The use of a separate, non-sample wash is not taught or suggested, limiting the versatility of assays of this invention. Likewise, Buechler does not teach or suggest the creation of a second flow path. The time gate in Buechler functions as a delay mechanism in a fluid path, not to redirect fluid flow or to permit different fluids to flow sequentially through a reaction zone. The methods and devices of Buechler et al. do not allow one to use multiple reagents, different wash and substrate reagents and cannot be used in an enzyme amplified assay.
Vonk, U.S. Pat. No., 5,185,127 discloses a filter stack comprising a hydrophilic membrane (containing a binder for an analyte) above a hydrophobic membrane above an absorbent material. The membrane is impermeable to the sample but permeable to a wetting agent (e.g. acetone, surfactants, detergents, or alcohols, most preferably methanol) mixed with the sample. Sample is added to the device and trapped above the hydrophobic member. Thereafter the wetting agent is added, which when mixed, allows the sample mixture to permeate into the absorbent material. Wash and substrate may be added. Other disadvantages of this device are that it (1) does not teach or suggest a defined fluid path for residual sample or wash, (2) does not permit controlled delivery of predetermined amounts of reaction components or wash, and (3) does not permit sequential delivery of such components.
Clark, U.S. Pat. Nos. 5,726,010, 5,726,013 and 5,750,333 (1998) describes assay methods and devices that use the formation of a solid phase bound tertiary complex to detect an analyte of interest in a fluid sample. A key feature of Clark is the use of a reversible flow in a chromatographic binding assay. An analyte-containing solution is applied to the device and then is transported by capillary flow, first in one direction and then in the opposite direction, along an elongated flow matrix. The flow matrix includes four different regions. Region one is where the analyte-containing solution is mixed with a labeled antibody. Region two, also called the detection zone, contains the second antibody, which is immobilized to a solid phase. Region three contains a site to apply a wash solution. Region four contains an absorbent reservoir located near region one and makes the flow go in the opposite direction. A means to detect the presence or quantity of an analyte is also included in the device. Clark does not automate steps. The user must measure the sample volume, apply it to the device, monitor and control timers, and physically activate the device. The mechanism for reversing flow does not allow for automated timing.
Assays and devices of the present invention overcome the shortcomings of the prior art and offer maximum results without user sample measurement or intervention beyond a single activation step. Assays of this invention may be particularly adaptable to situations where simultaneous detection of multiple analytes in a sample is desirable. Assays of this invention are in a unit dose format, stable, capable of room temperature storage, reliable, easy to manufacture and use, and available for a low cost per test. They have fully integrated packaging for both liquid and dried reagents. In addition, the claimed devices are self-timing for the delivery of reagents so there is minimal operator involvement.
DEFINITIONS
Analyte—The molecule to be detected. For example, an analyte as used herein, may be a ligand, a single compound or a plurality of compounds that share at least one epitopic site to a receptor or an antibody.
Capillarity—The movement of a liquid in contact with a solid that results due to adhesive and cohesive forces and surface tension. Capillarity can be affected by the solid surface, the liquid surface, or both.
Hydrophobic surface—Any surface not effectively wetted by water or an aqueous sample.
Hydrophillic surface—Any surface wetted by water or an aqueous sample.
Conjugate soluble binding reagent—Reagent(s) deposited and dried on a solid support, i.e., the sample delivery channel, and have a specific binding affinity for or chemical reactivity with the analyte of interest. Upon sample application, the conjugate soluble binding reagent becomes dissolved and can begin to flow. Conjugate soluble binding reagent can react with analyte, if present in the sample. Depending upon the assay format, one conjugate soluble binding reagent can be labeled with a detectable label and another with a binding reagent. These different assay formats will be described in more detail below.
Solid phase zone—A material or a surface at the intersection of at least two fluid flow paths.
Sample/conjugate mixture—The liquid mixture comprising the sample solution and solubilized conjugate binding reagents.
Immobilized capture reagent—A molecule that is bound to a solid support and has a specific binding affinity for or chemical reactivity with either the analyte of interest, or can be a receptor for one of the conjugate reagents e.g. avidin.
Sample delivery channel—The hydrophilic means where the conjugate soluble binding reagents are dried and the means through which the liquid sample flows.
Socklet—The hydrophilic mesh material that contains the solid phase when a particulate solid phase is used.
Solid phase—The hydrophilic material to which the immobilized capture reagent is bound.
Second fluid path material—The hydrophobic material that provides the secondary flow path. Examples of second fluid path material are bibulous material, plastic, or any other hydrophobic polymers. As the surface active agent-containing wash solution flows through the second fluid path material, the surface tension is reduced and allows sample/conjugate mixture to flow through the second fluid path material, which is now rendered hydrophilic.
Wash reagent—A liquid reagent that serves to remove unbound material from the solid phase region. As used herein, the wash reagent contains a surface active agent, such as a surfactant, or any other component capable of allowing the wash to wet a hydrophobic surface. Some other examples of wash reagents are alcohol, e.g. methanol, or any other water miscible organic solvents.
Substrate reagent—A liquid reagent that serves to facilitate analyte detection by causing a detectable color reaction. A secondary function of substrate reagent is to remove unbound material
Barski, Jr. Stanislaw
Clark Scott M.
Kepron Michael R.
Suva Robert H.
Workman, Jr. Erwin F.
Ceperley Mary E.
Idexx Laboratories Inc.
McDonnell & Boehnen Hulbert & Berghoff
Padmanabhan Kartic
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