An enzyme-linked immunosorbent assay (ELISA) is used to detect the presence of an antigen in a sample. The antigen is immobilized to the well of a plate by adsorption, or captured with a bound, antigen-specific antibody. A detection antibody is then added forming a complex with the antigen, if present. The detection antibody can be covalently linked to an enzyme, or itself be detected by a secondary, enzyme linked antibody. Enzyme substrate is then added to the wells producing a visible signal that is correlated with the amount of antigen and measured by a spectrophotometer.
Sandwich ELISA Summary
For general ELISA reference only.
For ELISA/EIA kit-specific protocol questions, please refer to the kit instructions, or email email@example.com.
- 100 ul peptide (@4ug/ml) in coating buffer is added to individual wells of a microtiter plate. Incubate the plate for 2 hours at 37C or overnight at 4C.
- Remove the coating solution and wash the plate three times by filling the wells with 100 ul PBS-0.05%Tween20. The solutions or washes are removed by flicking the plate over a sink. The remaining drops are removed by patting the plate on a paper towel.
- Block the remaining protein-binding sites in the coated wells by adding 100ul blocking buffer, 3% skim milk in PBS per well. Incubate for 1 hour at RT with gentle shaking.
- Wash the plate three times with 100ul PBS-0.05% Tween 20.
- Add 50 ul of diluted antibody to each well. Incubate the plate at 37C for an hour with gentle shaking.
- Wash the plate six times with 100ul PBS-0.05%Tween 20.
- Add 50ul of conjugated secondary antibody, diluted at the optimal concentration (according to the manufacturer) in blocking buffer immediately before use. Incubate at 37C for an hour.
- Wash the plate six times with 100ul PBS-0.05%Tween20.
- Prepare the substrate solution by mixing acetic acid, TMB and 0.03% H2O2 with the volume ratio of 4:1:5.
- Dispense 50ul of the substrate solution per well with a multichannel pipe. Incubate the plate at 37C in dark for 15-30mins.
- After sufficient color development, add 100ul of stop solution to the wells (if necessary).
- Read the absorbance (optical density at 450nm) of each well with a plate reader.