Eliza or enzyme-linked immuno sorbent
assay is also known as enzyme
immunoassay. It is a biochemical
technique to detect and quantify
compounds like antigens, antibodies and
hormones.
The amount of compound in the
sample corresponds to the amount of
substrate converted to colored product
by enzyme-linked antibody. Eliza is a
quick and sensitive method to quantify
large number of samples.
In one go Eliza
has successfully replaced a radio isotope
based radio amino acid or tria. It is
useful to diagnose HIV, rotavirus, syphilis, Zika virus and many others.
For ELIZA test we need a microtiter
plate consisting of multiple wells
coated with polystyrene which
facilitates the adsorption of compound
to the plate. The compound to be detected
which may be an antigen, hormone or
antibody, primary antibody that
specifically binds to the compound.
As I'm linked secondary antibody which is
specific for the primary antibody and
also converts its colorless substrate to
a colored product. The color produced is
quantified by calorimeter.
The intensity
of color corresponds to the amount of
compound in the given sample.
Three most
common types of Eliza are
- Direct Eliza
- Indirect Eliza
- Sandwich Eliza
In the Direct Eliza compound is attached
to the polystyrene plate. Enzyme-linked
antibody is added which binds to the
compound. A wash is given to remove
unknown antibody. Now substrate is added
which is converted by enzyme-linked
antibody to produce colored product and
measured by calorimeter.
In Indirect
Eliza the compound is attached to the
plate. Primary antibody is added which
binds to the compound. A wash is given
secondary antibody which is linked to
the enzyme is added which binds to the
primary antibody.
Again a quick wash is
given. Now substrate is added which is
converted to the colored product by the
enzyme.
Sandwich Eliza's little different. In
this instead of the compound anti
boarding is fixed to the plate. Now the
compound is added. Its antibody specific
compound is present it will bind to the
antibody.
Now primary antibody is added
which binds another epitope of the
compound to form a sandwich. A Vash is given, enzyme-linked secondary
antibody is added which binds to the
primary antibody.
Again a wash is given. Now the substrate is added which is
converted into the colored product and
detected by the detector.
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