Ligand-Binding Assays Immunoassays

Table 6.1 Ge neral differences between chromatographic methods (HPLC and LC-MS/MS) and ligand-binding assays (immunoassays).

DELFIA , developed by Wallac/PerkinElmer, Inc, is a quite powerful technique not only in usual immunoassays but also in receptor-ligand binding assays. Quite interestingly,... 

Ansell, R.J. MIP-ligand binding assays (pseudo-immunoassays). Bioseparation 2002,10, 365-377. 

There should be specific, saturable binding to the receptor, accompanied by pharmacological characteristics appropriate to the functional effects, demonstrable using a radioactive, eg, tritium or iodine-125, ligand to label the receptor. Radioligand binding assays (1,6) have become a significant means by which to identify and characterize receptors and enzymes (see Immunoassays Radioactive tracers). Isolation of the receptor or expression of the receptor in another cell, eg, an oocyte can be used to confirm the existence of a discrete entity. 

For the determination of these compounds a binding inhibition immunoassay, consisting of the competitive immunoreaction of the unbound antibody present in an analyte-antibody mixture with the hapten derivative immobilized at the sensor surface, has been applied. With the aim of assuring the regeneration and reusability of the surface without denaturation of the immobilized molecule, the formation of an alkanethiol monolayer was carried out to provide covalent attachment of the ligand to the functionalized carbodiimide surface in a highly controlled way. For DDT, the assay sensitivity was evaluated in the 0.004 - 3545 pg/l range of pesticide concentration by the determination of the limit of detection 0.3 pg/1 and the I50 value 4.2 pg/1. 

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