Highly sensitive immunosensor for Hepatitis B surface antigen detection based on a novel signal amplification system of gold nanorods and mesoporous Au@Pd@Pt core-shell nanospheres

In this work, a highly sensitive sandwich-type electrochemical immunosensor was fabricated by using the gold nanorods (Au NRs) as the substrate material and the mesoporous Au@Pd@Pt core-shell nanospheres (m-Au@Pd@Pt) as the label of the detection antibodies (Ab(2), Ab(2) label) for detecting Hepatitis B surface antigen (HBs Ag). The Au NRs with excellent conductivity and biocompatibility can accelerate the electron transfer on the electrode interface and enhance the load capacity of capture antibodies (Ab(1)). The m-Au@Pd@Pt with mesoporous structure can not only provide high specific surface area and abundant catalytically active sites, but also offer great pore accessibility of guest species from outside. The detection signal of the immunosensor was effectively improved by the novel Ab(2) label. With the good cooperation between Au NRs and Ab(2) label, a linear relationship between current signal and the logarithm of the HBs Ag concentration was obtained in the wide range of 20 fg/mL to 200 ng/mL and the detection limit of HBs Ag was 6.7 fg/mL (signal-to-noise ratio of 3). Besides, the designed immunosensor shows good reproducibility, long-term stability and high specificity. Crucially, the sensitive and selective response to HBs Ag in real human serum samples confirms that the designed immunosensor will be promising in the clinical diagnosis of biomarkers.