Chemistry: analytical and immunological testing – Involving diffusion or migration of antigen or antibody
Reexamination Certificate
1999-05-05
2002-11-26
Nguyen, Bao-Thuy L. (Department: 1641)
Chemistry: analytical and immunological testing
Involving diffusion or migration of antigen or antibody
C422S051000, C422S051000, C422S070000, C422S082010, C422S082030, C422S098000, C422S091000, C422S110000, C427S213300, C427S213340, C427S213350, C436S516000, C436S518000, C436S530000, C436S541000, C435S003000, C435S007100, C435S287700, C435S970000, C204S166000, C204S286100, C204S288000, C204S290010
Reexamination Certificate
active
06485983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to a system, test method and test strip for electrochemical quantitative analysis of one or more analytes in a test sample. More specifically, this invention is directed to an electrochemical quantitative analysis system for determination of an analyte (e.g. proteins, hormones or enzymes, small molecules, polysaccharides, antibodies, nucleic acids, drugs, toxins, viruses or virus particles, portions of a cell wall and other compounds which have specific or characteristic markers that permit their identification) within a solid phase (e.g. test strip) by measurement of electrochemical changes of label(s) associated with a labeled substance that can be correlated with the concentration of the analyte of interest. The test strip used in this analytical system includes a solid phase affinity chromatographic medium, having an electrochemical detection system associated therewith, within the fluid pathway through said medium. The inventions hereinafter set forth in detail are applicable to quantitative analysis of virtually any analyte, whose concentration can be correlated with an electroactive species of an electroactive substance that is capable of manifesting a change in electrical response within the electrochemical cell-like environment of the test strip of this invention.
2. Description of Prior Art
A. Immunodiagnostics
Immunochemical analysis for an analyte within a solid phase (test strip) generally involves an assay in which an analyte, in a liquid sample, and a labeled substance, interact with each other, or another reaction constituent. Within the context of the prior art, it is understood that a “labeled substance” can, thus, include (a) an analyte mimic that is labeled with an indicator, (b) a labeled ligand that is specific for interaction with the analyte of interest, or (c) a complex that is formed by interaction of (a) or (b) and yet another reaction constituent. The liquid containing the labeled substance and the analyte is then transferred to a porous film or membrane, where it is drawn by diffusion or capillary action along a fluid pathway of the membrane, and encounters one or more companion test kit reagents (at least one of which is immobilized within a definitive area thereof). This labeled substance and/or the analyte is thereafter captured by an immobilized companion test kit reagent at a test site to form a complex. If the complex is present in sufficient concentration, it produces a discernible change at such site. Where the indicator is a pigment, such as a metal (e.g. colloidal gold), or alternatively, a colored latex particle, the discernible change is generally visible to the naked eye.
The following patents are regarded as representative of this type of immunochromatographic assay. These patents are arranged in chronological order and no significance is to be attached to their order of discussion as to the patentability of the invention described and claimed herein.
Campbell et al, U.S. Pat. No. 4,703,017 (assigned to Becton Dickinson) describes a test method for detection of an analyte with a “direct” or “particulate” indicator, specifically an indicator that can be visually detected with the naked eye, thus, making such test method acceptable for home diagnostic use; or, alternatively, in a clinical setting devoid of sophisticated analytical equipment. The direct indicator of choice is a liposome containing a pigment or equivalent colorant. The claimed test method is described as suitable for urine analysis of analytes (e.g. pregnancy test); and, thus, capable of detection of an elevated level of analyte. Accordingly, such assay is regarded as a semi-quantitative determination of the analyte of interest. Because the test involves a single step (e.g. application of the sample to the test strip), the test has become characterized in the art as a “Rapid” test.
Rosenstein, U.S. Pat. No. 5,591,645 (assigned to Becton Dickinson) describes an immunochromatographic test method based upon the principles described in commonly assigned U.S. Pat. No. 4,703,017 (to Campbell et al). The Rosenstein test device incorporates all of the test kit reagent in the “same plane” of the test strip and contemplates applying the sample directly to the test strip to reconstitute the reagents contained therein and, thereby effect the desired analysis. The direct indicator of choice can be selected from a number of equivalent colorants, however, colloidal gold adsorbed to a binding protein (e.g. antibody or antigen) is generally preferred. The claimed test method is described as suitable for urine analysis of analytes (e.g. pregnancy test); and, thus, capable of detection of an elevated level of analyte or a semi-quantitative determination of the analyte of interest. Because the test also involves a single step (e.g. application of the sample to the test strip), the test has become characterized in the art as a “Rapid” test.
Swanson et al, U.S. Pat. No. 5,073,484 (assigned to Abbott laboratories) describes an immunochromatographic test method utilizing multiple test zones, with each zone arranged along a common linear fluid pathway. As the test sample and test kit reagents migrate along this fluid pathway, the analyte of interest (generally associated with a direct indicator) becomes bound to an immobilized companion reagent in each of the test zones. Each of the test zones is precalibrated in reference to a standard, and thus the appearance of color in specific test zone correlated with the concentration level of analyte in the sample. Accordingly, the concentration of the analyte in the sample can be estimated from the level of color development along the fluid pathway of the test device. Because the test also involves a single step (e.g. application of the sample to the test strip), the test has become characterized in the art as a “Rapid” test.
May et al, U.S. Pat. No. 5,602,040 (assigned to Unilever Patent Holdings) describes an immunochromatographic test method analogous to the test methods described in the Campbell et al and Rosenstein patents discussed above. One of principles differences identified and claimed by May et al, is the lyophilization of a sugar, along with the direct indicator, in the sample receiving site. The sugar addition is reportedly required to effect reconstitution of the lyophilized indicator and thus permit its interaction with the analyte in the sample.
With the limited exception of the adaptation of the foregoing Rapid Tests to detection of an elevated level of analyte, these Rapid Tests are generally unsuitable for precise quantitative monitoring an analyte level, or for the quantitative detection and differentiation of more than one analyte within a single test environment.
B. Instrumental Analysis
Analysis of fluid samples has also traditionally involved the use of instrumentation and the measurement of changes in electrical potential and/or current at given site/electrode. Typically, the electrical measurement is referenced to a second electrode, and a number of measurements made over a given interval and/or defined range of conditions.
The following patents are regarded as representative of this type of electrochemical analysis. These patents are arranged in chronological order and no significance is to attach to the order of discussion, or to their relative significance to the patentability of the invention described and claimed herein.
Wang U.S. Pat. No. 5,292,423 (assigned to New Mexico State University Technology Transfer Corp.) describes a method and apparatus for trace metal analysis of fluid samples (e.g. drinking water, blood, urine etc.) by means of initial adsorption of the trace metal from a fluid sample onto a screen printed carbon (working) electrode that had been pre-coated with mercury. The Wang test platform also employs at least one additional (reference) electrode. The electrode having the trace metal was, thereafter, subjected to analysis by either Anodic Stripping Voltammetry (ASV) or Potentiometric Stripping Analysis (PSA). The reported a
Lu Fang
Lu Frank N. W.
Wang Kai Hua
Faro John H.
Intec Science, Inc.
Nguyen Bao-Thuy L.
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