Determination of tumor marker CA125 by capillary electrophoretic enzyme immunoassay with electrochemical detection Original Research Article

A novel capillary electrophoretic enzyme immunoassay with electrochemical detection (CE-EIA-ED) was developed for a tumor marker cancer antigen 125 (CA125). In this method, after the noncompetitive enzyme immunoreaction, the free enzyme (horseradish peroxidase)-labeled anti-CA125 antibody (Ab∗) and the bound enzyme-labeled complex (Ag–Ab∗) were separated in a separation capillary and then catalyzed the enzyme substrate (3,3,5,5-tetramethyl-benzidine dihydrochloride, TMB(Red)) and H2O2 in a reaction capillary following the separation capillary. The product of the enzymatic catalysis reaction (TMB(Ox)) was amperometrically detected on a carbon fiber microdisk bundle electrode. A activity concentration limit of detection (LOD) of 0.29 U/ml, which corresponded to a activity LOD of 1.6 μU was achieved. The assay could be used to determine CA125 in human serums from ovary tumor patents.