ELISA (Enzyme-linked Immunosorbent Assay)

Summary

This video explains the Enzyme-Linked Immunosorbent Assay (ELISA) process, a plate-based technique used to detect and quantify soluble substances like proteins. It details how antigens are immobilized and detected by enzyme-coupled antibodies, which then produce a measurable colorful product from a colorless substrate. The video also covers different types of ELISA, including direct, indirect, and sandwich ELISA, and provides an example walkthrough of a sandwich ELISA.

Highlights

Introduction to ELISA00:00:00

ELISA (Enzyme-Linked Immunosorbent Assay) is a plate-based technique for detecting and quantifying soluble substances such as proteins. It involves immobilizing an antigen, which is then specifically detected by enzyme-coupled antibodies. These enzymes convert a colorless substrate into a measurable colorful product.

Basic Principle of ELISA00:00:33

In an ELISA, an antibody is attached to the bottom of a well, specifically designed to bind a protein of interest. A second, soluble, enzyme-conjugated antibody also specific for the target protein is then added. When a substrate is introduced, the enzyme converts it to a colorful product that can be measured.

Types of ELISA00:01:03

There are several variants of ELISA. In direct ELISA, the antigen is immobilized directly, and an enzyme-linked antibody binds to it. Indirect ELISA uses a primary antibody to bind the antigen, followed by a secondary enzyme-linked antibody that binds the primary antibody. The most common type is the sandwich ELISA, where a primary antibody captures the antigen, and a second primary antibody specifically binds the same antigen.

Commonality Among ELISA Types00:01:45

Regardless of the ELISA type, the last antibody binding step is always conjugated to an enzyme, confirming the binding of the target substance.

Example: Sandwich ELISA Walkthrough00:01:55

An example of a sandwich ELISA involves two wells, both coated with primary antibody specific for protein X. One well receives a sample containing the protein, and the other serves as a control without the target protein. After initial binding and a wash step, enzyme-linked antibodies are added, binding to the antigen in the sample well. A final wash is performed, and then a colorless substrate is added. The enzyme in the sample well converts the substrate into a measurable, colorful product, while the control well remains colorless, allowing for quantification using spectrophotometry.