Chemistry: analytical and immunological testing – Involving an insoluble carrier for immobilizing immunochemicals
Reexamination Certificate
1999-06-14
2003-03-04
Nguyen, Bao-Thuy L. (Department: 1641)
Chemistry: analytical and immunological testing
Involving an insoluble carrier for immobilizing immunochemicals
C435S007100, C435S007220, C435S007210, C435S007920, C435S287100, C435S287600, C435S287200, C435S287700, C435S810000, C435S970000, C435S974000, C435S975000, C436S164000, C436S165000, C436S169000, C436S514000, C436S528000, C436S530000, C436S805000, C436S807000, C436S808000, C436S810000, C436S811000, C436S817000, C422S051000, C422S051000, C422S051000, C422S051000, C422S067000
Reexamination Certificate
active
06528323
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to lateral flow test strips and methods of operation for the lateral flow test strips.
2. Description of Related Art
Quantitative analysis of cells and analytes in fluid samples, particularly bodily fluid samples, often provides critical diagnostic and treatment information for physicians and patients. For example, immunological testing methods which take advantage of the high specificity of antigen-antibody reactions, provide one approach to measurement of analytes. Kennedy, D. M. and S. J. Challacombe, eds., ELISA and Other Solid Phase Immunoassays: Theoretical and Practical Aspects, John Wiley and Sons, Chichester (1988). This document and all others cited to herein, are incorporated by reference as if reproduced fully below. Such assays may also find use in various other applications, such as veterinary, food testing, or agricultural applications.
Immunoassays that provide a quantitative measurement of the amount of an analyte in a sample have previously used complex, multi-step procedures and expensive analyzers available only in a laboratory setting.
Immunochromatographic assays, such as those described in GB 2,204,398A; U.S. Pat. Nos. 5,096,837, 5,238,652, and 5,266,497; Birnbaum, S. et al., Analytical Biochem. 206:168-171 (1992); Roberts, M. A. and R. A. Durst, Analytical Chem. 67:482-491 (1995); and Klimov, A. D. et al., Clinical Chem. 41:1360 (1995), are simpler, yet do not provide a quantitative measurement of an analyte. Instead, these immunochromatographic assays detect the presence (or absence) of an analyte above a defined cutoff level the test performed. The lack of a quantitative measurement limits the usefulness of these assays.
A variety of disposable diagnostic assay devices have also been developed. Examples of such devices include, but are not limited to Cathey, et al, U.S. Pat. No. 5,660,993; International Publication Number WO 92/12428; Eisinger, et al, U.S. Pat. No. 4,943,522; Campbell, et al, U.S. Pat. No. 4,703,017; Campbell, et al, U.S. Pat. No. 4,743,560; and Brooks, U.S. Pat. No. 5,753,517.
SUMMARY OF THE INVENTION
A test strip is provided which is adapted to receive a sample and detect an analyte therein. According to one embodiment, the test strip comprises a sample addition zone to which a sample may be added; an absorbent zone proximal to the sample addition zone; one or more test zones distal to the sample addition zone, at least one of the test zones including a first analyte binding agent immobilized therein which is capable of binding to the analyte to be detected; and a terminal sample flow zone distal to the one or more test zones, the absorbent zone being positioned relative to the sample addition zone and having an absorption capacity relative to the other zones of the test strip such that a distal diffusion front of a sample added to the sample addition zone diffuses from the sample addition zone to a distal diffusion point within the terminal sample flow zone and then reverses direction and diffuses proximal relative to the one or more test zones.
In another embodiment, a test strip is provided which comprises a sample addition zone to which a sample may be added; an absorbent zone proximal to the sample addition zone; one or more test zones distal to the sample addition zone, at least one of the test zones including a first analyte binding agent immobilized therein which is capable of binding to the analyte to be detected; a terminal sample flow zone distal to the one or more test zones, the absorbent zone being positioned relative to the sample addition zone and having an absorption capacity relative to the other zones of the test strip such that a distal diffusion front of a sample added to the sample addition zone within the predetermined volume range diffuses from the sample addition zone to a distal diffusion point within the terminal sample flow zone and then diffuses proximal relative to the one or more test zones; and a conjugate buffer addition zone distal to the terminal sample flow zone to which a conjugate buffer may be added.
According to the above test strip embodiment, the conjugate buffer addition zone may be positioned relative to the test zones such that conjugate buffer added to the conjugate buffer addition zone at the same time as sample is added to the sample addition zone reaches the distal diffusion point after the distal diffusion front of the sample has diffused to the distal diffusion point and begun diffusing in a proximal direction. The conjugate buffer addition zone may also be positioned relative to the test zones such that conjugate buffer added to the conjugate buffer addition zone at the same time that the sample is added to the sample addition zone reaches the test zones after the distal diffusion front of the sample diffuses proximal relative to the test zones. The conjugate buffer addition zone may also be positioned relative to the test zones such that the conjugate buffer can be added to the test strip before the sample and nevertheless reach the distal diffusion point after the distal diffusion front of the sample has diffused to the distal diffusion zone, reversed direction and begun diffusing in a proximal direction.
According to any of the above test strip embodiments, the test strip may include 1, 2, 3 or more test zones with one or more control binding agents immobilized therein. In one embodiment, the test strip comprises at least a first control zone with a control binding agent immobilized therein. Optionally, the test zones further include a second control zone with a same control binding agent immobilized therein as the first control zone, the first control zone containing a different amount of the control binding agent than the second control zone.
Also according to any of the above test strip embodiments, a second analyte binding agent which is capable of binding to the analyte and diffusing to the one or more test zones may be included on the test strip. Alternatively, second analyte binding agent may be delivered to the test strip via the conjugate buffer. The second analyte binding agent may bind to components in the sample other than the analyte. Alternatively, the second analyte binding agent may be an agent which does not bind to components in the sample other than the analyte.
In order to facilitate detection, the second analyte binding agent is preferably labeled with a detectable marker. As discussed herein, any of a wide range of detectable markers known in the art may be used. In a preferred embodiment, the second analyte binding agent is attached to a particle which is capable of diffusing to the one or more test zones. The particle may serve as the detectable marker or may itself be labeled with a detectable marker.
A method is also provided for detecting an analyte in a sample. In one embodiment, the method comprises delivering a sample to a test strip which causes a distal diffusion front of the sample to (a) diffuse in a distal direction to one or more test zones, at least one of the test zones including a first analyte binding agent immobilized therein which binds to analyte in the sample, (b) diffuse to a terminal sample flow zone distal to the one or more test zones, change direction and (c) diffuse to a position proximal to the one or more test zones; delivering a conjugate buffer to the test strip at a position distal to the terminal sample flow zone, delivery of the conjugate buffer causing a second analyte binding agent to diffuse proximally past the terminal sample flow zone to the one or more test zones after the distal diffusion front of the sample diffuses proximal to the one or more test zones, the second analyte binding agent binding to analyte immobilized in the test zones; and detecting the second analyte binding agent immobilized in the test zones.
According to the method, the conjugate buffer may be added to the test strip at a same time as the sample is added to the test strip, before the sample is added to the test strip, or after the sample is added to the test s
Dinello Robert K.
Polito Alan J.
Sierra George H.
Thayer Richard M.
Wieck Henry J.
Nguyen Bao-Thuy L.
Praxsys Biosystems, Inc.
Robins & Pasternak LLP
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