Amperometric carbohydrate antigen 19-9 immunosensor based on three dimensional ordered macroporous magnetic Au film coupling direct electrochemistry of horseradish peroxidase

• Three dimensional ordered macroporous magnetic electrode was newly used in electrochemical immunosensor.
• The large surface area of macroporous magnetic electrode could improve the immobilized amount of antibody.
• Au nanoparticles functionalized SBA-15 was used to immobilize enzyme labeled Ab2 and enzyme.
• Macroporous magnetic electrode and Au nanoparticles composite facilitated the direct electron transfer of enzyme.
• The immunoassay avoided adding electron transfer mediator, simplifying the procedure.

A sandwich-type electrochemical immunosensor for the detection of carbohydrate antigen 19-9 (CA 19-9) antigen based on the immobilization of primary antibody (Ab1) on three dimensional ordered macroporous magnetic (3DOMM) electrode, and the direct electrochemistry of horseradish peroxidase (HRP) that was used as both the label of secondary antibody (Ab2) and the blocking reagent. The 3DOMM electrode was fabricated by introducing core–shell Au–SiO2@Fe3O4 nanospheres onto the surface of three dimensional ordered macroporous (3DOM) Au electrode via the application of an external magnet. Au nanoparticles functionalized SBA-15 (Au@SBA-15) was conjugated to the HRP labeled secondary antibody (HRP-Ab2) through the Au–SH or Au–NH3+ interaction, and HRP was also used as the block reagent. The formation of antigen–antibody complex made the combination of Au@SBA-15 and 3DOMM exhibit remarkable synergistic effects for accelerating direct electron transfer (DET) between HRP and the electrode. Under the optimal conditions, the DET current signal increased proportionally to CA 19-9 concentration in the range of 0.05 to 15.65 U mL−1 with a detection limit of 0.01 U mL−1. Moreover, the immunosensor showed high selectivity, good stability, satisfactory reproducibility and regeneration. Importantly, the developed method was used to assay clinical serum specimens, achieving a good relation with those obtained from the commercialized electrochemiluminescent method.

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