Wash-coating process, plate-type

A sandwich ELISA is used to search for a desired analyte in a test solution, as follows the solid phase is coated with analyte-specific capture antibodies to pull the analyte out of the test sample. After washing, the amount of analyte bound to the solid phase can be determined by adding an excess of enzyme-labelled analyte-specific antibody. The specificity of the method can be improved by using a sandwich-type, two-site assay, in which the capture and labelled antibodies have specificities for different parts of the analyte, as mentioned above. The performance of an immunoassay in a standard microtitre plate requires several hours. Such long incubation times are mostly linked to inefficient mass transport from the solution to the surface, whereas the immunocapture itself is a rapid process. 

The phage display library is now ready for use in an affinity selection protocol. Affinity selection has also been successfully utilized in vitro and ex vivo. The affinity selection principle is the same for all types of selection. First, allow the phage library to bind to the presented target. Wash away unbound phage, elute and amplify bound phage. Repeat the selection process three to four times. For example in vitro targets may be purified, biotinylated, and immobilized on a streptavidin-coated plate for affinity selection (9). 

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