A label-free immunosensor based on PtPd NCs@MoS2 nanoenzymes for hepatitis B surface antigen detection.

Nowadays, nanomaterials with enzymatic properties have aroused wide interest because of their special advantages, such as catalytic activity, simple preparation method and high stability. We introduced new nanoenzymes to a label-free electrochemical immunosensor for Hepatitis B surface antigen (HBs Ag) detection. In this study, PtPd nanocubes@MoS2 nanoenzymes (PtPd NCs@MoS2) were prepared by loading PtPd nanocubes (PtPd NCs) on molybdenum disulfide nano-sheet (MoS2) through in situ redox polymerization. The prepared nanoenzymes exhibited enhanced peroxidase-like activity than separate MoS2 and PtPd NCs. The catalytic process of PtPd NCs@MoS2 is in agreement with the Michaelis-Menten kinetic equation. PtPd NCs@MoS2 were used for sensitive detection of HBs Ag, which is ascribed to their superior peroxidase activity, good conductivity and high specific surface area and synergistic amplification for current signals. Compared with the detection limit of colorimetric method (3.3 pg/mL), the electrochemical method (10.2 fg/mL) shows a lower detection limit and a wider linear range from 32 fg/mL to 100 ng/mL, so it is more suitable for quantitative analysis of Hepatitis B. In summary, the prepared immunosensor provides a better opportunity for early diagnosis of Hepatitis B and also has further applications in biosensing and medical diagnostics.