Immunoassay method and kit

摘要

An immunoassay, e.g. ELISA, method and kit for determining (preferably quantitatively) an analyte adsorbed at a surface or present in a liquid sample, comprising binding said analyte to a solid phase, attaching a marker to the analyte, and detecting marker attached to said solid-phase. The invention proposes to use a combination of marker and detection means (e.g. an enzyme-substrate combination) which is capable of producing a precipitate on solid phase which carries the marker and to detect the binding of analyte to the solid phase by determining the change of surface mass of said solid phase due to the formation of said precipitate. Ellipsometry is an example of a technique suitable for determining the change of surface mass of the solid phase, which could be made of a silicon or chromium-sputtered glass slide. The invention shortens the assay time and/or improves the assay sensitivity, and allows to measure extremely low surface concentrations of analytes of interest.