An ultrasensitive sandwich-type electrochemical immunosensor based on the signal amplification system of double-deck gold film and thionine unite with platinum nanowire inlaid globular SBA-15 microsphere

- The D-Au film was first used in the immunosensor as substrate platform.
- A novel Pt NWs@g-SBA-15/Thi was first applied as an Ab2 labeled probe.
- The immunosensor exhibited a wide detection range and a low limit of detection.
- The immunosensor showed a promising capacity for applying in clinical detection.

A novel thionine unites with platinum nanowire inlaid globular SBA-15 (Pt NWs@g-SBA-15/Thi) not only utilizes as an efficient electrical signal probe but also constitutes an amplifying system with double-deck gold film (D-Au film) have been applied to the fabrication of sandwich-type immunosensor for detecting hepatitis B surface antigen (HBs Ag). The D-Au film can accelerate the electron transfer on the electrode interface due to the tunneling effect between the two Au films and can improve the load capacity of primary antibodies (Ab1) because of the good biocompatibility. The Pt NWs@g-SBA-15/Thi with uniform globular morphology not only can effectively reduce the spatial limitation for loading the secondary antibodies (Ab2) but also can provide outstanding pore accessibility of guest species from outside and offer catalytically active sites in a large scale. Besides, the presence of Thi can well enhance the electrical conductivity of Pt NWs@g-SBA-15/Thi. With the good cooperation between D-Au film and Pt NWs@g-SBA-15/Thi, a linear relationship between current signals and the concentrations of HBs Ag was obtained in the wide range from 10 fg/mL to 100 ng/mL and the detection limit of HBs Ag was 3.3 fg/mL (signal-to-noise ratio of 3). Furthermore, the designed immunosensor with excellent selectivity, reproducibility and stability shows excellent performance in detection of human serum samples and provides a promising capacity for detecting a wide range of other tumor markers in clinical application.