Lab & analytical techniques · Reference
What is ELISA?
ELISA (enzyme-linked immunosorbent assay) is an antibody-based laboratory assay that detects and quantifies a target molecule by linking its capture to an enzyme that produces a measurable colour change.
How the assay works
ELISA is carried out in the wells of a microplate. The target molecule (antigen) is immobilised on the well surface, either directly or by a capture antibody. A detection antibody linked to an enzyme then binds the target. After unbound material is washed away, a substrate is added; the enzyme converts it into a coloured or luminescent product. Because the enzyme turns over many substrate molecules, the signal is amplified, and its measured intensity is proportional to the amount of target captured. Comparing the signal with a standard curve gives a quantitative result.
Types of ELISA
Several formats exist. In a direct ELISA, a single enzyme-linked antibody binds the immobilised target. In an indirect ELISA, an unlabelled primary antibody binds the target and a labelled secondary antibody binds the primary, amplifying the signal.
In a sandwich ELISA, the target is held between a capture antibody and a detection antibody, giving high specificity. A competitive format measures targets that are too small to be sandwiched.
Uses in research
ELISA is a mainstay of biochemistry and immunology research, used to measure proteins, hormones, cytokines, and antibodies in laboratory samples. It complements antibody methods such as the Western blot and the cell-by-cell readout of flow cytometry. Reliable quantification depends on validated antibodies, a properly fitted standard curve, and documented controls, so that measured concentrations are accurate and comparable between laboratories.
Key facts
At a glance
- Full name: enzyme-linked immunosorbent assay
- Format: microplate (well-based)
- Specificity from: antibody binding to the target
- Signal: enzyme converts a substrate to a colour or light
- Main types: direct, indirect, sandwich, competitive
- Quantification: signal compared with a standard curve
Common questions
FAQ
What does ELISA stand for?+
ELISA stands for enzyme-linked immunosorbent assay. It uses antibodies to capture a target molecule and an enzyme to generate a measurable colour or light signal that reports how much target is present.
What is a sandwich ELISA?+
In a sandwich ELISA the target is held between two antibodies — a capture antibody fixed to the plate and an enzyme-linked detection antibody. Requiring two binding events makes the assay highly specific.
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