*hCG: Human chorionic gonadotropin
A Medic Aid REF : 854972. ISO 13485 Medical devices
homework for Frugal Science, Prakash Lab program
A common test is the detection of human chorionic gonadotropin (hCG), used in home pregnancy tests. This hormone is produced by the placenta. The release of hCG starts after the conception and increases during the first semester of pregnancy. The principle of this test is a direct lateral flow immunoassay and is explained below.
step 1: Sample (urine) is added on the the sample pad. The sample migrates through this region to the conjugate pad. If the sample contains hCG, this hCG will bind to the conjugate (mouse anti-hCG antibody-conjugate). Both hCG and conjugate migrate into the next section of the strip, which is the reaction matrix.
step 2: When hCG is present in the sample, it will bind to the anti- hCG capture antibodies on the test line. When enough of the hCG- conjugate complex binds to the capture antibody, a colored band will be formed on the test line. If the sample does not contain hCG, the test line will not be developed (fig. ii)
step 3: Regardless of the presence of hCG, the mixture continues to move across the membrane to the immobilized goat anti- mouse antibodies. A colored band at the control line will appear. The control line should always be visible (fig. i). When it’s not visible, the test is invalid.
Often : mouse monoclonal antibody to hCG conjugated with colloidal gold are coated in sensitized colloidal gold coating area in membrane filter in test strip