Chemistry: analytical and immunological testing – Involving an insoluble carrier for immobilizing immunochemicals
Reexamination Certificate
1999-05-10
2003-04-29
Chin, Christopher L. (Department: 1641)
Chemistry: analytical and immunological testing
Involving an insoluble carrier for immobilizing immunochemicals
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Reexamination Certificate
active
06555390
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a chromatographic assay or test device for detection and/or determination of an analyte in a sample, and in one particular embodiment it relates to a chromatographic assay device which incorporates an immunoassay in a procedure known as immunochromatography.
This invention has particular, but not exclusive, application in the detection of analytes in biological samples such as blood, urine, faecal and saliva samples, and the like.
BACKGROUND OF THE INVENTION
Prior International Patent Applications Nos. PCT/US92/00425(WO 92/21977) and PCT/US94/13982 (WO 95/16207) note that among the many analytical systems used for detection and/or determination of analytes, particularly analytes of biological interest, are chromatographic assay systems. Among the analytes of biological interest frequently assayed with such systems are:
1. hormones, such as human chorionic gonadotropin (hCG), frequently assayed as a marker of human pregnancy;
2. antigens, particularly antigens specific to bacterial, viral, and protozoan pathogens, such as Streptococcus, hepatitis virus, Giardia, feline leukaemia virus, tobacco mosaic virus, Salmonella, and Plasmodium;
3. antibodies, particularly antibodies induced as a result of infection with pathogens, such as antibodies to the bacterium
Helicobacter pylori
, to human immunodeficiency virus (HIV) and to feline immunodeficiency virus (FIV);
4. other proteins, such as haemoglobin, frequently assayed in determinations of faecal occult blood, an early indicator of gastrointestinal disorders such as colon cancer;
5. enzymes, such as aspartate amino transferase, lactate dehydrogenase, alkaline phosphatase, and glutamate dehydrogenase, frequently assayed as indicators of physiological function and tissue damage;
6. drugs, both therapeutic drugs, such as antibiotics, tranquillisers and anticonvulsants, and illegal drugs of abuse, such as cocaine, heroin, and marijuana;
7. vitamins; and
8. environmental contaminants, such as pathogens, herbicides, pesticides, toxic residues, and the like.
Such chromatographic systems are frequently used by physicians and medical technicians in the health field, and by agricultural and environmental professionals and technicians, for rapid point-of-care or on-site diagnosis, detection or monitoring of analytes of biological interest. They are also increasingly used by patients themselves for at-home monitoring of a variety of therapeutic conditions and disorders.
Among the most important of such chromatographic systems are the “thin layer” systems in which a solvent moves as a solvent front across a thin, flat absorbent medium. Among the most important of tests that can be performed with such thin layer systems are immunoassays, which depend on the specific interaction between an antigen or hapten and a corresponding antibody. The use of immunoassays as a means of testing for the presence and/or amount of clinically important molecules has been known for some time.
As previously noted chromatographic techniques used in conjunction with immunoassays are known as immunochromatography. In general, this technique uses a disclosing reagent or particle that has been linked to an antibody to the analyte to be assayed, forming a conjugate. This conjugate is then mixed with a specimen and, if the analyte to be assayed is present in the specimen, the disclosing reagent-linked antibodies bind to the analyte to be assayed, thereby giving an indication that the analyte to be assayed is present. The disclosing reagent or particle can be identifiable by colour, magnetic properties, radioactivity, specific reactivity with another molecule, or another physical or chemical property. The specific reactions that are employed vary with the nature of the analyte being assayed and the sample to be tested.
Although useful, currently available chromatographic techniques using test strips have a number of drawbacks. Many samples, such as faecal samples, contain particulate matter that can clog the pores of the chromatographic medium, greatly hindering the immunochromatographic process. Other samples, such as blood, contain cells and coloured components that make it difficult to read the test. Even if the sample does not create interference, it is frequently difficult with existing chromatographic test devices to apply the sample to the chromatographic medium so that the solvent front moves uniformly through the chromatographic medium to ensure that the sample reaches the area where binding is to occur in a uniform, straight-line manner.
Most immunochromatographic assay or test devices, because of their fixed and inflexible formats, are limited in their range of diagnostic applications. Most allow only unidirectional liquid flows and require that specimen or sample pre-treatments, such as antigen extraction, are carried out “off-board” or prior to addition to the assay or test device.
U.S. Pat. No. 5,415,944 (assigned to Quidel Corporation) discloses a closed test device which is adapted to allow “on-board” pre-treatment, or extraction, of a specimen on a swab. In this case, the swab is inserted into an extraction chamber, which is moulded as part of the housing of the test device. Extraction reagents are added to the swab and, after a period of time, unidirectional flow follows passively as the reagents migrate from the chamber to the wicking components of the immunochromatographic test system encased within the housing.
International Patent Application Nos. PCT/US92/04425 and PCT/US94/13982 (assigned to SmithKline Diagnostics, Inc.) mentioned above, disclose testing systems involving sample preparation means or test components placed on the opposing panels of an open two-panel test device. In this case, the test is only initiated or completed on bringing the two opposing panels together on closure of the test device.
It is an object of the present invention to provide an assay or test device utilising a chromatographic assay format, more particularly an immunochromatographic assay format, that is versatile as well as being simple and economic to manufacture. In particular, it is an object to provide an assay or test device that utilises a closed housing in association with a moveable or relocatable element that allows manipulation of liquid flows for initiation, modification and/or completion of the assay procedure.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the present invention, there is provided a chromatographic assay or test device for detection and/or determination of an analyte in a test sample, which comprises
(a) a base member, and
(b) a chromatographic medium located in or on said base member,
said base member being provided with a receptacle to receive an applicator having said sample applied thereto, said applicator being movable laterally when located in said receptacle between a first position in which said applicator located in said receptacle is out of fluid contact with said chromatographic medium, and a second position in which said applicator located in said receptacle is in fluid contact with said chromatographic medium so as to apply a sample on said applicator to said chromatographic medium.
In another aspect, the present invention provides a chromatographic assay or test device for detection and/or determination of an analyte in a test sample, which comprises
(a) a base member, and
(b) a second member,
at least one of said base member and said second member including a chromatographic medium, and said second member being movable laterally with respect to the base member from a first position to a second position, wherein in said first position a sample to be assayed applied to one of said base and second members is out of fluid contact with said chromatographic medium, and in said second position said sample is in fluid contact with said chromatographic medium.
In yet another aspect, the present invention provides a chromatographic assay or test device for detection and/or determination of an analyte in a sample, which comprises:
(a) a base member, and
(b) a second mem
Chin Christopher L.
Do Pensee T.
Lahive & Cockfield LLP
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