A sandwich enzyme immunoassay for cardiac troponin I.

A sandwich enzyme immunoassay for cardiac troponin I (caTnI) is a description which can identify injuries to the heart. Bovine cTnI was purified from bovine cardiac muscle, then an antibody against cTnI was prepared. We confirmed by immunoblotting that the anti-cTnI antibody reacted only to proteins extracted from the heart and in addition, only to cTnI among them. A mouse monoclonal anti-cTnI IgG-coated polystyrene ball was incubated with cTnI, and subsequently with affinity-purified rabbit anti-cTnI Fab-peroxidase conjugate. Specifically bound peroxidase activity was assayed by fluorometry. The detection limit was 3 fmol (84 ng) per assay. The cross-reaction of the sandwich enzyme immunoassay in regard to proteins from other organs was investigated. A little cross-reaction was recognizable only when proteins from skeletal muscle were in high concentration, but we supposed that this assay could be applied to identify injuries to the heart. We developed a sandwich enzyme immunoassay for bovine cTnI. However, further studies will be aimed at developing a sandwich enzyme immunoassay for human cTnI.