Now, exactly what IS ELISA?
It is a immunochemical test which is used to test for the presence of a specific antibody or antigen.
ELISA has 2 methods, direct, and indirect. First up in the spotlight is the direct method of ELISA
Direct method-
This tests for the presence of a specific antigen. The specific antibody is used to coat the walls of the wells on the plastic strip, using a coating solution. The positive sample, which contains the antigen is introduced into the well, where the antigen is bound to the antibody. This bond is strong enough to withstand the removal of the fluid and rinse.
Afterwich, the secondary enzyme is added in, which binds to the bound antigen. This secondary antigen has been modified, so that it has an enzyme attached onto it.
The contents are then rinsed once more, removing excess antibodies. The specific substrate for the enzyme is then added. This causes the enzyme to turn colour, which then turns the colour of the whole contents of the well.
Indirect method- This tests for the presence of a specific antibody. Thus, the antigen is used to coat the walls of the wells. The positive sample contains the antibody, which binds with the antigen. This complex formed withstands rinsing. An anitbody-enzyme conjugate, or reporter antibodies, bind to the antibody, froming a complex.
Rinsing takes place again, before the specific substrate for the enzyme is added, causing a colour change.
Uses:
ELISA can be used to determine the presence of a specific antigen and detect the presence antigenic properties. The following links will lead to an animation describing ELISA and a virtual lab.
I personally find that ELISA effective, as long as one got all the steps right and can save time, despite the time taken to complete the serial dilutions. And so, I final understand what is done with our blood and urine samples, though only a bit of our sample goes through this.
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