Ultrasensitive ratiometric electrochemical immunoassay of N-terminal pro-B-type natriuretic peptide based on three-dimensional PtCoNi hollow multi-branches/ferrocene-grafted-ionic liquid and Co-N-C nanosheets

Developing a simple and sensitive method for detecting tumor biomarkers is practically important for early diagnosis and clinical treatment of diseases. However, it is still the major challenge to improve the sensitivity and accuracy. Here, "a dual-signal read out mode" ratiometric electrochemical immunosensor was developed based on well-dispersed hierarchical PtCoNi hollow multi-branches (HMBs)/ferrocene-grafted-ionic liquid (Fc-g-IL, synthesized via Schiff-base reaction) and Co-N-C nanosheets (NSs, obtained by a simple pyrolysis method) as signal amplification. Specifically, the PtCoNi HMBs were synthesized by solvothermal treatment and then etched with acetic acid. The PtCoNi HMBs/Fc-g-IL showed improved catalytic property and superior biocompatibility. Meanwhile, Au nanostars/thionine decorated Co-N-C NSs (Au Thi Co-N-C NSs) performed as the label of secondary antibody (Ab(2)) to greatly enhance the signals. This immunoassay for N-terminal pro-B-type natriuretic peptide (NT-proBNP) was realized by boosting the Thi signals while inversely decaying the Fc responses, in turn showing the linear relationship towards the analyte in the range of 0.001-10.0 ng mL(-)(1) with the low detection limit down to 0.35 pg mL(-1) (S/N = 3). This study displays a promising platform for determination of other tumor biomarkers in real medical applications.