Chemistry: analytical and immunological testing – Involving diffusion or migration of antigen or antibody
Reissue Patent
1998-10-06
2004-02-17
Chin, Christopher L. (Department: 1641)
Chemistry: analytical and immunological testing
Involving diffusion or migration of antigen or antibody
C422S051000, C422S051000, C422S051000, C422S051000, C422S067000, C435S007100, C435S287100, C435S287200, C435S287700, C435S287800, C435S287900, C435S805000, C435S970000, C436S518000, C436S524000, C436S528000, C436S541000, C436S810000, C436S829000
Reissue Patent
active
RE038430
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an assay for an analyte, and more particularly to a solid phase assay.
FIELD OF THE INVENTION
Assays for various analytes have been accomplished by a so-called solid phase assay. In a solid phase assay, a binder specific for at least the ligand to be determined (analyte) is supported on a solid support, whereby, in the assay it is not necessary to employ an additional agent for separating the bound and free phases formed in the assay.
In general, such solid supports have been in the form of tubes, solid particles, and in some cases, the solid phase has been in the form of a “dip-stick”.
In a dip-stick solid phase assay, a binder may be supported the dip-stick with the dip-stick, containing the binder, being dipped into an assay solution containing the analyte, and in general, such solution further contains a tracer. The presence and/or amount of tracer on the dip-stick is then employed as a measure of analyte (either a qualitative or quantitative measure of analyte).
The present invention is directed to providing an improved solid phase assay for determining analyte, and more particularly to a solid phase assay.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a solid support having a first portion and a second portion with the first and second portions being in capillary flow communication with each other whereby material flows by capillarity. The first and second portions are positioned on the solid support in a manner such that the first portion may be contacted with material, including any analyte, with material in said first portion being transported by capillarity from the first portion of the support to the second portion thereof.
The second portion of the solid support includes a binder which is a binder for at least the analyte, with the binder also being a binder for a tracer used in the assay, when the assay format is a so-called competitive assay format.
The solid support also includes a tracer, which is comprised of a ligand portion and a detectable label portion conjugated to the ligand portion of the tracer. In the case where the assay format is a so-called competitive assay format, the ligand portion of the tracer is bound by the binder contained in the second portion of the solid support. In the case where the assay format is a so-called sandwich assay format, the ligand portion of the tracer is bound by the analyte.
The tracer is supported on the solid support on a tracer portion of the solid support in a manner such that when wetted, the tracer is capable of being transported by capillarity to the second portion of the solid support, and thereafter, depending on the presence and/or absence of analyte and/or the amount of analyte, as hereinafter explained in more detail, to a third portion of the solid support.
The tracer portion of the solid support may be a separate portion of the solid support or may be the first portion of the solid support (the portion to which sample is added).
The binder which is supported on the second portion of the solid phase is supported in a manner such that the binder remains immobile and is not transported by capillarity to the third portion of the solid support.
The third portion of the solid support may be a portion for detecting tracer which has been transported by capillarity from the second portion to the third portion. The third portion may or may not include a substance supported thereon for detecting tracer. Alternatively, the third portion may function only to receive materials not bound in the second portion.
In accordance with the present invention, the amount of tracer which is immobilized in the second portion of the solid support by being bound either directly to the binder in the second portion (in a competitive assay format), or by being indirectly bound to the binder (tracer is bound to analyte which is bound to the binder in a sandwich assay format) is dependent upon the presence and/or amount of analyte in the sample. In a so-called sandwich assay format, the amount of tracer which is passed from the second portion to the third portion of the solid support by capillarity is indirectly proportional to the amount of analyte in the sample, and in the so-called competitive assay format, the amount of tracer which passes from the second portion to the third portion of the solid support, by capillarity, is directly proportional to the amount of analyte in the sample.
In a preferred embodiment of the present invention, the solid support and the various components are produced and employed in a manner for determining analyte by a competitive assay format, with the tracer being supported on the first portion of the solid support.
In a particularly preferred embodiment, as hereinafter explained in more detail, the detectable label portion of the tracer is comprised of a sac or lipid vesicle (often referred to as a liposome), which includes a detectable label.
In employing a preferred embodiment wherein the assay is a competitive assay, the tracer is supported on the solid support on the first portion thereof, and the first portion of the solid support is wetted with the sample containing analyte to be determined. Upon wetting of the solid support with the sample, both sample and tracer flow by capillarity into the second portion of the solid support which contains a binder specific for both the analyte and tracer, with the binder being immobilized on the second portion of the solid support. Depending upon the presence and/or amount of analyte in the sample portion, tracer becomes bound to the binder on the second portion of the solid support. The tracer which is not bound by the binder on the second portion, then flows by capillarity into the third portion of the solid support for detection and/or determination therein. If the assay format is to be a simple “yes or no” format (only determining whether or not analyte is present in the sample), then the binder supported on the second portion of the solid support is supported in an amount such that in the absence of a detectable amount of analyte in the sample, there is no detectable presence of tracer in the third portion of the solid support. As should be apparent, as the amount of analyte in the sample increases, the amount of tracer which is not bound to the binder in the second portion of the solid support increases, thereby increasing the amount of tracer present in the third portion of the solid support. Accordingly, a quantitative assay may be run by determining tracer which remains in the second portion of the solid support and/or which flows by capillarity into the third portion of the solid support, and comparing such detected amount of tracer in the second and/or third portion with a “standard curve” to determine the amount of analyte in the sample. Thus, is an assay the determination of tracer and/or analyte may be either qualitative or quantitative.
In the sandwich assay format, tracer is preferably supported on a tracer portion of the solid support which is different from the first portion of the solid support. The ligand portion of the tracer is bound by the analyte, with the binder in the second portion of the solid support being specific for the analyte. The first portion of the solid support is contacted with the sample containing analyte, and the tracer portion of the solid support is wetted to cause both the tracer and analyte to flow by capillarity to the binder supported by the second portion of the support. The amount of tracer which becomes bound to analyte is directly proportional to the amount of analyte in the sample, and tracer bound to analyte, as well as any unbound tracer, flow by capillarity to the second portion of the solid support. In the second portion of the solid support, analyte becomes bound to immobilized binder specific for the analyte, with the unbound tracer (tracer not bound to analyte which is bound to the immobilized binder) flows by capillarity to the third portion of the solid support. The tracer on the third portion of
Becton Dickinson and Company
Chin Christopher L.
Fitzpatrick ,Cella, Harper & Scinto
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