A facile ratiometric electrochemical strategy for ultrasensitive monitoring HER2 using polydopamine-grafted-ferrocene/reduced graphene oxide, Au@Ag nanoshuttles and hollow Ni@PtNi yolk-shell nanocages

[Display omitted] •Hollow Ni@PtNi yolk-shell nanocages were prepared by the solvothermal and subsequent etching treatment.•The incorporation of rich Thi into Ni@PtNi HNCs greatly enhanced the detection signals.•FcBA was efficiently grafted on PDA via covalent linkage between boracic acid of FcBA and vicinal diol of PDA.•The rGO-PDA-Fc functionalized with Au@Ag NSs demonstrated the outstanding analytical performance in immunoassay of HER2. Human epidermal growth factor receptor 2 (HER2) is believed as a clinically important breast cancer marker, and thereby it is extremely imperative to develop a highly sensitive and effective strategy for specific recognition and assay of HER2. In this work, a facile ratiometric electrochemical immunosensor was fabricated for sensitively monitoring HER2 as a model analyte, in which reduced graphene oxide-polydopamine-grafted-ferrocene/Au@Ag nanoshuttles (Au@Ag NSs) performed as electrode material and hollow Ni@PtNi yolk-shell nanocages-thionine (Ni@PtNi HNCs) as signal tags, which provided two distinct electrochemical signals from Fc and Thi, respectively. The Au@Ag NSs endowed the rGO-PDA-Fc with improved biocompatibility and dramatic magnification of the Fc signals upon sensing interface. Also, by integration of the hollow structure, enlarged specific surface area and superior catalytic ability together, the Ni@PtNi HNCs-Thi achieved substantial amplification in the detection signals from Thi. Benefiting from the above, the as-developed immunosensor exhibited a broad linear range (0.01 ∼ 100 ng mL–1) and a low detection limit (3.3 pg mL–1) for HER2 (S/N = 3), followed by exploring its application in actual serum samples with acceptable results. It holds great potential for clinical screening of cancer biomarkers and point of-care assays.