Bimetallic cerium and ferric oxides nanoparticles embedded within mesoporous carbon matrix: Electrochemical immunosensor for sensitive detection of carbohydrate antigen 19-9

A label-free electrochemical immunosensor was successfully developed for sensitively detecting carbohydrate antigen 19-9 (CA19-9) as a cancer marker. To achieve this, a series of bimetallic cerium and ferric oxide nanoparticles embedded within the mesoporous carbon matrix (represented by CeO2/FeOx@mC) was obtained from the bimetallic CeFe-based metal organic framework (CeFe-MOF) by calcination at different high temperatures. The formed CeO2 or FeOx nanoparticles were uniformly distributed within the highly graphitized mesoporous carbon matrix at the calcination temperature of 500 °C (represented by CeO2/FeOx@mC500). However, the obtained nanoparticles were aggregated into large size when calcined at the temperatures of 700 and 900 °C. The CA 19-9 antibody can be anchored to the CeO2/FeOx@mC network through chemical absorption between carboxylic groups of antibody and CeO2 or FeOx by ester-like bridging. The CeO2/FeOx@mC500-based immunosensor displayed superior sensing performance to the pristine CeFe-MOF, CeO2/FeOx@mC700- and CeO2/FeOx@mC900-based ones. Electrochemical impedance spectroscopy results showed that the developed immunosensor exhibited an extremely low detection limit of 10 μU·mL-1 (S/N = 3) within a wide range from 0.1 mU·mL-1 to 10 U·mL-1 toward CA 19-9. It also illustrated excellent specificity, good reproducibility and stability, and acceptable application analysis in the human serum solution which was diluted 100-fold with 0.01 M PBS solution (pH 7.4) and spiked with different amounts of CA19-9. Consequently, the proposed electrochemical immunosensor is capable enough of determining CA 19-9 in clinical diagnostics.