ABSTRACT
During the last decades, “binding” assays like receptor assays or immunoassays played a major role in biology. Thousands of assays have been developed in different areas such as diagnostic, pharmaceutic, environmental and food. Compounds measured by “binding” assays cover all kinds of chemical products : peptides (1), polysaccharides (2), lipids (3), nucleic acids (4) or synthetic organic chemicals. Assays have been set up to detect molecules as small as dopamine or to measure high molecular complexes such as viruses. The first methods were limited to radio-assays using non-purified sources of ligands (1). Today, the technological choice is unlimited integrating ligand preparation, detection system and the solid phase. For immunological methods polyclonal, monoclonal (5) as well as recombinant antibody fragments (6) can be employed. Various solid phases like tubes, microtiterplates, microparticles or membranes are used for the separation step (7,8). Isotopic, colorimetric, fluorometric or luminometric techniques are applied to detect binding reactions (8). All these detection systems are based on antibody (or antigen) labeled by a chemical modification. In 1991, BIAcore, a biosensor based on optical detection, was introduced. This system allows the detection of molecular interactions in real time and without labeling.
