A sandwich-type electrochemical immunosensor based on Au@Pd nanodendrite functionalized MoO₂ nanosheet for highly...

In this work, a sandwich-type electrochemical immunosensor was fabricated to the effective detection of hepatitis B surface antigen (HBsAg). The designed electrochemical immunosensor was based on Au core and Pd shell nanodendrites loaded on amino functionalized molybdenum dioxide nanosheets (Au@Pd NDS/NH₂-MoO₂ NSs) as the secondary antibody (Ab₂) label and silver nanoparticles were loaded by electrodeposited (D-Ag NPs) on the surface of electrode as the platform. Because of the synergistic effect and abundant catalytic activity sites provided by surface dendrite structure, Au@Pd NDs were more effective than single gold and palladium nanoparticles in catalytic reduction of hydrogen peroxide (H₂O₂). MoO₂ had the good catalytic capacity for reduction of H₂O₂ and favourable electrical conductivity. Hence, the obtained Au@Pd NDS/NH₂-MoO₂ NSs were more effective than Au@Pd NDs and NH₂-MoO₂ NSs in catalytic reduction of hydrogen peroxide attribute to a synergistic effect. Also, Ag NPs with admirable electrical conductivity and biocompatibility were used as sensing platforms and primary antibodies (Ab₁) carriers, which can accelerate the electron transfer and improve the sensitivity of the immunosensor. Here, the proposed electrochemical immunosensor offered a wide linear interval from 10 fg mL^-1 to 100 ng mL^-1 and the lower limit of detection of 3.3 fg mL^-1 (S/N = 3) for detection of HBsAg under optimal experimental conditions. Furthermore, the accuracy of the actual serum sample analysis was satisfactory, which showed that the electrochemical immunosensor possessed a good application prospect in clinical detection.