Enhanced catalytic amplification of mesoporous bismuth-gold nano-electrocatalyst triggering efficient capture of...

A new sandwich-type electrochemical immunosensor for the sensitive detection of carcinoembryonic antigen (CEA) was originally developed using a unique bismuth (Bi)-gold (Au) nano-electrocatalyst triggering efficient capture of tumor marker, where the nano-electrocatalyst was obtained by implanting Au nanoparticles (Au NPs) inside the mesoporous NBiOF nanospheres (Au@NBOF NSs) for the purpose to marker secondary antibody (Ab₂) and amplify the response signal through electrochemically catalyzing the reduction of hydrogen peroxide. The synergistic interaction between NBOF NSs and Au NPs endowed the as-received Au@NBOF nano-electrocatalyst with large electrocatalytic active surface area and powerful signal amplification function as upper sandwich layer to conjugate Ab₂. The multi-walled carbon nanotubes sparkled with Au nanostars served as the lower sandwich layer to capture the primary antibody (Ab₁), which enhanced the interfacial electron transport and the load capacity of Ab₁ as a result of increasing the sensing response of the designed immunosensor based on the sandwich-type Ab₁-CEA-Ab₂ interaction. Such immunosensor proposed on the above double signal amplification strategy efficiently detected the target CEA in a wide concentration range from 100 fg mL^-1 to 200 ng mL^-1. The detection limit was as low as 9.57 fg mL^-1 with excellent specificity and reproducibility. The satisfactory results in analyzing human serum samples indicate the potential application of this new immunosensor in early clinical diagnosis of cancer and the evaluation of treatment efficiency.