Synthesis of a new biacridine and its use as the chemiluminescent probe for immunoassay of carcinoembryonic antigen

A new biacridine compound, 10,10ʹ-dimethyl-3,3ʹ-disulfo-9,9ʹ-biacridine (DMDSBA) was synthesized, and its chemiluminescent characteristics were investigated in detail. DMDSBA was used to label anti-CEA antibody. The labeling ratio was estimated to be 1.15–1.32, and the average labeling ratio was 1.25. The results show that there are no obvious changes in the immunoreactivity of the labeled anti-CEA antibody and the quantum efficiency of DMDSBA after attaching to the anti-CEA antibody. In addition, the conditions of labeling reaction, sandwich immunoassay and chemiluminescent reaction have been studied. A new sandwich chemiluminescent immunoassay method was firstly established, and used to determine CEA in human serum, the calibration range is 1.0–100 ng ml^-1 and the minimal detectable concentration of CEA is 0.53 ng ml^-1, the relative standard deviation is 6.5% for 20 ng ml^-1 CEA. This method was well-matched with radio immunoassay.