ELISA (English name: Enzyme-linked Immunosorbent Assay), is a biochemical technique that exploits the capturability and enzyme catalytic property of antibody to enzyme linked protein. ELISA method includes three steps: Step 1 : Coating plate with antigen or antibody; Step 2 : Adding antibody or antigen; Step 3 : Adding enzyme marker to detect antibody-antigen binding; If a solid phase is used to fix the antigen or antibody in each step, the assay is called sandwich assay.
ELISA is a biochemical technique that exploits the capturability and enzyme catalytic property of antibody to enzyme linked protein. ELISA can be used to detect antigen or antibody in a sample.
The principle of ELISA is based on the use of antibodies that bind to specific antigens and enzymes. The bound antibodies are then detected by a second antibody labeled with an enzyme, which catalyzes a chemical reaction that generates colored products.
The principle of this method is that the antigen can specifically interact with its corresponding antibody, and the antigen antibody complex will form, which can be detected by enzyme label. The method of ELISA is as follows:
Plates 1–4 are coated with antigen or antibody. The plates should be coated with antigen or antibody. This can be done by incubation or by adding the antigen or antibody to the plate. The method depends on the type of antigen or antibody (i.e., liquid form vs dry).
The plates are carefully sealed, and then incubated at room temperature for about one hour. This allows the antibody to bind to the antigen on the plate. At this point, it's time for another wash! A special solution is used to remove unbound antibody or antigen by washing away excess fluid from around each well in your plate.
Once you've added your antibody, you need to add an enzyme marker to detect the presence or absence of enzyme. Enzyme markers can be used to detect whether an enzyme has reacted with something it's supposed to react with. They're usually fluorescent or radioactive, but sometimes they can be color-changing as well.
A sandwich assay is an enzyme-linked immunosorbent assay (ELISA), in which a solid phase is used to fix the antigen or antibody in each step. The enzyme marker is added to detect the antigen or antibody.
The two types of sandwich assays are direct and indirect. In direct sandwich assays, a fixed amount of purified antigens or antibodies are immobilized on a solid support, such as plastic microtitre plates or beads; then excess free binding sites are blocked by incubation with an excess concentration of non-immune serum (or other blocking agent) before adding a sample containing suspected anti-body. After washing away unbound materials, only those bound to immobilized specific antigens or antibodies will remain as detected by enzymatic reaction at their unreacted sites for detection with appropriate substrate solutions which produces coloured product proportional to amount present.
There are two types of detection methods in ELISA technology, one is indirect detection method and the other is competitive detection method.
Indirect Detection Method: First, the antigen-antibody complex is formed, and then the enzyme label is added to detect the antigen-antibody complex. The antigen antibody reaction can be detected by adding some diagnostic enzymes such as peroxidase or alkaline phosphatase into it. The enzyme label will react with the product of these reactions to produce a colored product (usually blue).
Competitive Detection Method: First, an anti-body is added to the plate at high concentration so that when you add your unknown material sample there will be no free antibody for binding your specific epitope on your unknown material and thus you cannot detect anything!
ELISA is a widely used immunoassay. It is based on the ability of an antigen or antibody to interact with a specific complementary antigen or antibody. The interaction between specific antigen and antibody can form immune complex, which will be detected by ELISA coating solution or conjugate that contains enzyme, resulting in color change that depends on the degree of conversion of substrate into product (Figures 1, 2).
ELISA (enzyme-linked immunosorbent assay) is a widely used immunoassay which is based on the ability of an antigen or antibody to interact with a specific complementary antigen or antibody, and has been widely used for antigen or antibody detection in serum, body fluids and cells.
The specific complementary combination of antigen and antibody can form immune complex, which is generally insoluble in the reaction solution. By determining the concentration of insoluble immune complex, the content of antigen or antibody in solution can be determined.
The principle and method of ELISA:
The principle of ELISA is based on the ability of an antigen or antibody to interact with a specific complementary antigen or antibody, which is generally insoluble in the reaction solution. By determining the concentration of insoluble immune complex, we can determine whether there is any antigen or antibody present in body fluids. If there are no antigens, then there will be nothing for antibodies to react with; if there are no antibodies, then antigens cannot be detected. Thus, it is easy to determine whether there are any specific substances present in body fluids by using immunoassay techniques like ELISA.
ELISA (Enzyme-Linked Immunosorbent Assay) is a widely used immunoassay that measures the concentration of an antigen or antibody in solution. The principle of ELISA is based on the ability of an antigen or antibody to interact with a specific complementary antigen or antibody. When you have specific complementary combination of antigen and antibody, it forms immune complex, which can be detected by adding enzyme-labeled anti-immunoglobulin A (IgA) antibodies.
ELISA is a widely used immunoassay which stands for Enzyme-Linked Immunosorbent Assay. It's based on the ability of an antigen or antibody to interact with a specific complementary antigen or antibody and is widely used for antigen or antibody detection.
ELISA is a sensitive, specific and convenient method to detect the antigen or antibody. It requires only one step of antigen-antibody interaction, the detection is easy and fast, but it is not suitable for quantitative detection of small amount of antigen or antibody. The principle of ELISA is based on the enzyme reaction with substrate, which can be detected by spectrophotometry.