Immunoassays
What are immunoassays?
Immunoassay diagnostic technology is based on a biological reagent called an antibody. Antibodies are created by the immune system. The immune system evolved as a defense mechanism to protect the host animal’s body from pathogens. Specific antibodies are produced by the immune system in response to the presence of a specific foreign material. In the body, antibodies specifically bind the foreign substance and mark it for destruction. Since antibodies are capable of binding only certain substances, the binding event can be used to determine if a specific substance is present in a diagnostic sample. This phenomenon is called specificity. All immunoassays take advantage of an antibody’s binding specificity to provide diagnostic results. For specific mycotoxin or GMO detection, EnviroLogix prepares antibodies that bind only to certain mycotoxins or GMO proteins. There are two general types of immunoassays: sandwich assays and competitive assays. Sandwich assays and competitive assays can be utilized in lateral flow device or Enzyme-Linked Immunosorbent Assay (ELISA) formats.
To learn more about different types of immunoassays, visit our knowledgebase post.
What are lateral flow devices?
EnviroLogix' QuickStix and QuickTox lateral flow test devices (LFDs) employ the same immunoassay principles as ELISA plate and tube formats, but coat antibodies or other reagents on a nitrocellulose membrane rather than on the inside of test wells or tubes. The sample is added at one end of the LFD strip and travels by capillary action to the other end, similar to a pregnancy test. As the fluid sample travels through the membrane, the sample is exposed to zones of antibody reactive to the target analyte (what the test is designed to detect). The QuickStix/QuickTox assays are designed to develop a "control line" near the far end of the device. The control line ensures the device is functioning properly.
ELISA
What are ELISA tests?
ELISA or Enzyme-Linked ImmunoSorbent Assay, is a high throughput immunoassay format. The most common ELISA is performed in a 96 well microtiter plate. Each well is coated with an antibody, and either a sandwich assay or competitive assays is performed. In the sandwich assay, the other antibody is linked to an enzyme capable of creating a color change. In the competitive assay, the enzyme is linked to the same analyte that the test is designed to detect and a competition to bind the antibody attached to the plate occurs.
A microtiter plate reader is used to measure the optical density of each test well at the end of the assay. ELISA methods have been widely used in medical applications since the early-70’s. Countless studies have demonstrated the correlation between ELISA results and traditional methodologies such as gas chromatography (GC) and high performance liquid chromatography (HPLC).