Highly sensitive competitive electrochemiluminescence immunosensor based on ABEI-H 2 O 2 system with cobalt hydroxide nanosheets and bimetal PdAg as co-enhancer for detection of florfenicol.

A competitive electrochemiluminescence immunoassay was established based on the isoluminol-H 2 O 2 (ABEI-H 2 O 2 ) system catalyzed by cobalt hydroxide (Co(OH) 2 ) to detect florfenicol residues in food. First , ultra-thin two-dimensional Co(OH) 2 nanosheets were used as the catalyst of ABEI-H 2 O 2 system, and excellent catalytic effects were acquired by catalytic decomposition of hydrogen peroxide with cobalt ions. Then, bimetal PdAg (Pd/Ag) alloy nanoparticles were used as a bridge to connect ABEI and antibody due to their good biocompatibility; Pd/Ag alloy nanoparticles also had a catalytic effect to further amplify the ECL signal in the system due to the synergistic catalytic effect of the bimetal. A competitive immunoassay strategy was used to detect florfenicol, where the florfenicol in the sample will compete with the antibody for the limited binding sites on the coating antigen. The ECL immunosensor for florfenicol detection shows high sensitivity, with a linear range from 10 -4   to 10 2  ng mL -1 , and a detection limit of 3.1 × 10 -5  ng mL -1 , where the scan potential was varied from 0 to 0.6 V vs Ag/AgCl . This work was the first to use Co(OH) 2 nanosheets and bimetal PdAg catalytic signal amplification methods to design the sensor, which provides a novel, convenient and reliable strategy for ultra-sensitive detection of florfenicol, and other biological small molecules. A novel ECL immunosensor based on ABEI-H 2 O 2 2 .