12/5/2023 0 Comments Orderlateral flow tests![]() The ELISA technology was developed in 1971. There was an explosion of activity in this field after 1945. LFTs derive from paper chromatography, which was developed in 1943 by Martin and Synge, and elaborated in 1944 by Consden, Gordon and Martin. LFTs can operate as either competitive or sandwich assays. After passing these reaction zones, the fluid enters the final porous material, the wick, that simply acts as a waste container. The control line contains affinity ligands which show whether the sample has flowed through and the bio-molecules in the conjugate pad are active. The test line shows a signal, often a color as in pregnancy tests. This marks target particles as they pass through the pad and continue across to the test and control lines. The conjugate pad contains all the reagents required for an optimized chemical reaction between the target molecule (e.g., an antigen) and its chemical partner (e.g., antibody) that has been immobilized on the particle's surface. Once soaked, the fluid flows to the second conjugate pad in which the manufacturer has stored freeze dried bio-active particles called conjugates (see below) in a salt–sugar matrix. The sample pad acts as a sponge and holds an excess of sample fluid. Each of these pads has the capacity to transport fluid (e.g., urine, blood, saliva) spontaneously. The pads are based on a series of capillary beds, such as pieces of porous paper, microstructured polymer, or sintered polymer. In essence, these tests run the liquid sample along the surface of a pad with reactive molecules that show a visual positive or negative result. LFTs operate on the same principles of affinity chromatography as the enzyme-linked immunosorbent assays ( ELISA). Because the target substance is often a biological antigen, many lateral flow tests are rapid antigen tests (RAT or ART). Many lab-based applications increase the sensitivity of simple LFTs by employing additional dedicated equipment. These tests are simple and economical and generally show results in around five to thirty minutes. ![]() For instance, the home pregnancy test is an LFT that detects a specific hormone. LFTs are widely used in medical diagnostics in the home, at the point of care, and in the laboratory. It is a simple device intended to detect the presence of a target substance in a liquid sample without the need for specialized and costly equipment. Immunochromatographic testing devices A NASA illustration of a lateral flow assayĪ lateral flow test ( LFT), is an assay also known as a lateral flow device (LFD), lateral flow immunochromatographic assay, or rapid test.
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