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

A new biacridine compound, 10,10′-dimethyl-3,3′-disulfo-9,9′-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.