Assays and devices therefor

Details Assays and devices therefor Assays and devices therefor

1988-11-22

1993-01-26

Rosen, Sam

Chemistry: analytical and immunological testing

Involving an insoluble carrier for immobilizing immunochemicals

422 56, 422 57, 422 58, 422 60, 422 61, 436528, 436535, 436536, 436807, 436810, 436817, 436818, G01N 33543, G01N 33549

Patent

active

051822164

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to assays and to devices in which such assays can be conducted.
The invention is particularly applicable to assays utilising specific binding, such as immunoassays in which an analyte is assayed by virtue of its participation in a so-called "sandwich" reaction. In a sandwich reaction, the analyte forms a bridge between two reagents which bind specifically with the analyte. Typically one such reagent is fixed to a solid phase, such as a particulate carrier material or to a surface e.g. a peg, and the second reagent is readily soluble or dispersible in a liquid medium (e.g. a medium containing the analyte to be assayed). The second reagent provides a means for determining the extent to which the sandwich binding reaction has taken place. Many examples of such systems are known and used in a wide variety of assay tests. In a very typical example, the second reagent is linked to a chemical marker, such as an enzyme, which is allowed to participate in a chemical reaction following the specific binding step and the chemical reaction produces an observable result, such as a colour change or colour formation.
Conventionally, the sandwich reaction is performed sequentially with the fixed reagent being contacted with the sample, and following an appropriate incubation period to allow the reagent to pick up the analyte, the solid phase is removed from the sample and contacted with the second reagent so that the sandwich reaction can be completed.
A simpler procedure would involve having both of the specific binding reagents present with the sample and permitting the sandwich reaction to take place in a single incubation. One step in the conventional procedure would then be avoided This simpler procedure, often referred to as simultaneous marking, performs well under most circumstances but can prove unreliable if the sample to be analysed contains a high concentration of the analyte. A phenomenon, known as the "hook effect", then occurs. The high concentration of analyte saturates both of the specific binding reagents and the necessary bridge between the two specific binding reagents is not always formed. When the extent to which the specific binding reaction has occurred is assessed, a spuriously low result is observed because only a proportion of the labelled specific binding reagent has been linked via a single analyte molecule to the specific binding reagent linked to the solid phase. Pregnancy tests in which the analyte is HCG are examples of assays in which the "hook effect" can be a significant problem. There is therefore a need for a simultaneous marking sandwich assay, the reliability of which is independent of the concentration of analyte in the sample. The present invention provides a simultaneous marking assay system wherein a first specific binding reagent immobilised on a solid phase carrier is simultaneously incubated with a liquid sample suspected of containing an analyte to which the binding reagent is specific and with a second binding reagent dissolved or dispersed in the liquid sample bearing a label by means of which an analytical result can be determined and which second binding reagent is also specific for the analyte and which can therefore cooperate with the first binding reagent in a "sandwich" reaction, wherein prior to the incubation the second specific binding reagent is contained within a layer of solid material superimposed on the sensitised surface (i.e. the surface on which the first specific binding reagent is immobilised) of the solid phase, and which material is readily soluble or dispersible in the liquid sample. When the solid phase is contacted with a liquid sample and the solid material layer dissolves or disperses, the entrapped labelled reagent is released into the liquid sample and the immobilised reagent is simultaneously exposed to the liquid sample. The close proximity of the two reagents ensures that there is a high chance of them cooperating in a "sandwich" reaction with any analyte molecules in the sample, even when the analyte is in high c

REFERENCES:
patent: 4742011 (1988-05-01), Blake et al.

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