A direct ELISA (enzyme-linked immunosorbent assay) is a plate-based immunosorbent assay intended for the detection and quantification of a specific analyte (e.g. antigens, antibodies, proteins, hormones, peptides, etc.) from within a complex biological sample.
Of the four different forms of ELISA, direct ELISA is the easiest and fastest to perform. There are many companies available from where you can easily buy bdnf elisa kit online.
In direct ELISA, antigen is immobilized directly on the surface of a multi-well microtiter plate, such as a 96-well polystyrene plate, and then complexed with an antigen-specific enzyme-labeled primary antibody.
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Once the enzyme-labeled primary antibody binds to the antigen, the conjugated primary antibody catalyzes the reaction with the appropriate substrate, producing a visible colorimetric output as measured by a spectrophotometer or absorbent microplate reader.
Direct ELISA is suitable for qualitative and quantitative antigen detection in the desired sample, for antibody screening and for epitope mapping.
The most obvious advantage of direct ELISA over indirect ELISA is that only one antibody is required, and less time is required to complete the assay. The second advantage is that the possibility of non-specific cross-reactivity of the secondary antibody is completely eliminated.
In ELISA, the antigen (target macromolecule) is immobilized on a hard surface (microtiter plate) and then complexed with an antibody that binds to the reporter enzyme. Detection is carried out by measuring the activity of the reporter enzyme by incubation with a suitable substrate to obtain a measurable product.