Immuno-gold lateral flow assay

Abstract

A chromatographic lateral-flow assay system for rapid, high sensitivity method of detecting low levels of ligands in body fluids, with few false positives and few false negatives. The lateral-flow assay may have a membrane strip in ribbon form, which increases detection on the order of 2 to 10 fold over the conventional chromatographic specific binding assay techniques by placing a dried or lyophilized conjugate in colloidal spheres opposite side of the lateral flow membrane strip. A chromatographic specific binding assay strip device, comprising: a laminate strip having a first side and an second side; a conjugate pad or membrane disposed on said first side of said laminate; a hinge region connecting sample receiving pad or membrane strip and reservoir pad or membrane disposed on said second side of said laminate; wherein said laminating material isolates the conjugate pad from the sample pad such as to slow the fluid path into the fibrous sample pad, and a detection pad or membrane strip disposed between the sample pad or membrane and the reservoir pad or membrane on said first side of said laminate. The more complete mixing permitted by this temporary obstruction provides an important feature of the invention that gives this 2-step test its superior performance. The assay system comprises a housing device, such as a test tube or cassettes to facilitate the mixing of a sample solution with the dried or lyophilized conjugate, and kits.

Description

[0001] This application is a continuation-in-part (CIP) of Ser. No. 11 / 248,214, filed on Oct. 13, 2005, pending, and claims benefit of this earlier filing date under 35 U.S.C. §120, the contents of which are herein incorporated by reference to the extent allowed by law.FIELD OF INVENTION [0002] The present invention generally relates to an assay system and apparatus involving specific binding of analytes and / or ligands, and specifically relates to chromatographic flow binding assays with a colored conjugate, and a novel lateral-flow-platform that includes a dried or lyophilized colloidal sphere conjugate, such as gold, to the back of the lateral flow test. BACKGROUND OF THE INVENTION [0003] It is increasingly desirable to provide a rapid high sensitivity system to detect low levels of ligands in body fluids, plant extracts, environmental samples, tissue samples and enrichment broths. Ideally, such systems should have a minimal number of procedural steps and yield reliable results, e...

AI Technical Summary

Benefits of technology

[0019] The present invention generally relates to a rapid high sensitivity system apparatus and method for detecting low levels of ligands in body bio-fluids, environmental and tissue culture extracts, with high sensitivity and specificity.

[0021] Another aspect of the invention includes the placement of the sample port on the same side of the test cassette as the visualization window for simplicity and convenience. The laminating material over the sample pad or membrane serves as a temporary obstruction or impedes in the flow path of a sample solution, resulting in the sample and conjugate label to be in contact for a longer amount of time before flowing out of the conjugate pad. This allows for a more thorough or complete mixing of the conjugate and sample solution before it enters the sample pad or membrane. Preferably gold colloidal spheres are used as conjugates, but other metal sols and latex microparticles may be used as well.

Problems solved by technology

To a significant extent, many known tests presently available for detecting ligands are either time consuming, labor intensive, or in need of instrumental assistance to read results.

Most known tests also lack an acceptable degree of sensitivity or specificity.

False positives may be troublesome, particularly with agglutination and other rapid detection methods such as dipstick and color change tests.

Nevertheless, these techniques have not solved all problems related to sensitivity, neither have they been reliable in obtaining results with a minimal number of method steps encountered in these rapid detection methods.

Unfortunately, while these devices are somewhat useful, they suffer from limitations in capture efficiency and sensitivity because most of the analyte in a sample flows around or through the reaction site on the capture material.

A major disadvantage of all of the known prior art is that the sample rehydrates the dried conjugate along the flow path.

Thus, a severe limitation of the one-step lateral flow assay is the limited amount of sample actually involved in the reaction with the conjugate.

None of the known prior art teach or suggest locating the conjugate pad or membrane on the reverse side of the strip, and not in contact with either the sample receiving pad or the membrane.

Further, in a one-step lateral flow assay, as a sample mixes with a dry conjugate, incomplete mixing often yields conjugate particles with vastly different numbers of captured analyte molecules.

These tests have a significant drawback though.

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