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Elisa Protocol | Step by step procedure of Elisa test technique

Elisa Protocol is sequential and has an orderly procedure to be followed out in carrying the test.

Elisa test is an immunoassay which relies on the interaction between specific antibody and antigen.

For detailed principle check “ELISA TEST PRINCIPLE“.

For this, factors like time of reaction, interfering substances, temperature, pH, buffer composition, treatment, washing’s play an important role in the successful outcome of the assay.

Hence the Elisa assay requires to be carried out in particular sequence and operating procedure for best results.

Any deviation from this Elisa protocol can affect the results greatly and sometimes one may even fail to get proper results.

Most ELISA tests are done using commercially available ELISA kits which have definite protocol mentioned on a leaflet.

These kits, in general, contain an antibody tagged with an enzyme, a substrate reagent, Elisa plates with wells i.e. 96 places or few, washing buffer, etc and also a step by step Elisa protocol for the given sample.

These kits once received are to be stored at recommended temperatures for long-life of the kit’s contents.

Once opened, the contents of the Elisa kit are to be used within a specified time or short life mentioned by the supplier for effective analysis.

Elisa Protocol steps:

• Take out the contents in ELISA kit on to suitable work table inside a temperature-controlled room or lab. Then wash the ELISA plate and let it dry (do only if recommended in the protocol brochure of the kit from supplier).

• The given test sample under analysis is taken preferably in a homogenate or solution form.

• A fixed volume of the test sample is drawn into a micropipette and loaded into the wells of Elisa plate.

• The samples are placed in such a way to accommodate a blank, a standard (if available) and test sample in the wells of the Elisa plates.

A brief video  demo for competitive ELISA procedure

• Then wait for a specified time, preferably half-hour for the antigens in the sample to fix to the walls of the well.

• Next, rinse (wash) the samples inside the wells with buffer. This step removes unbound part of the sample from the wells, i.e. only antigens remain fixed on the wall of the well in Elisa plates.

• Then the fixed volume of enzyme-linked anti-body is placed into the washed wells and allowed to stay for a half-hour. This lets firm binding of enzyme-linked antibodies with antigens if any fixed to the walls of the wells.

• Again rinse the wells with washing buffer to remove any unbound enzyme-linked antibodies.

• Now load the washed wells with a specified amount of Elisa substrate and incubate for a specified time for the reaction to proceed and generate a color.

• In the meantime switch on the Elisa instrument or Elisa plate reader and set the defined wavelength filter. Mark the sample locations on the plate wells on the computer screen i.e. blanks, standards, and test sample’s positions to avoid later confusion.

• After the time of incubation, immediately place the plate into the socket of the Elisa instrument, close the socket door and take the reading after detection.

The reading can be had in an excel sheet or print out based on the Elisa instrument you use.

Then discard the used plate. That’s the end of Elisa protocol.

It is so simple and can be done in a couple of hours without much strain…

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