A novel electrochemical immunosensor for hepatitis B surface antigen based on Fe₃O₄ nanoflowers and heterogeneous chain reaction signal amplification strategy

Herein, a novel sandwich-type electrochemical immunosensor was fabricated based on Fe₃O₄ nanoflowers (Fe₃O₄ NFs) and heterogeneous chain reaction (HCR) signal amplification strategy for the sensitive detection of hepatitis B surface antigen (HBsAg). The aldehyde-functionalized Fe₃O₄ NFs are used as a supporting matrix to immobilize the hepatitis B surface antibody 1 (HBsAb1). The biotin-modified single-strand DNA (biotin-S0) was connected onto the biotin-HBsAb2 via linkage of streptavidin (SA), followed by addition of methylene blue (MB) modified single strand DNA1 (MB-S1) and DNA2 (MB-S2) for HCR signal amplification. The designed immunosensor exhibited a detection linear range of 0.5 pg mL⁻¹-0.25 ng mL⁻¹ and a low detection limit of 0.16 pg mL⁻¹, with excellent stability, selectivity and reproducibility. Furthermore, HBsAg is detected in the serum samples with a stable and fast response, indicating that the proposed immunosensor has a promising potential application in clinical analysis.