A dual-type responsive electrochemical immunosensor for quantitative detection of PCSK9 based on n-C₆₀-PdPt/N-GNRs...

In this study, a dual-type responsive electrochemical immunosensor was developed for the quantitative detection of proprotein convertase subtilisin/kexin type 9 (PCSK9), a potential biomarker of cardiovascular disease in serum. N-doped graphene nanoribbons (N-GNRs) with good conductivity were used as the sensing matrix modifying the glassy carbon electrode. Palladium platinum alloy (PdPt) nanoparticles with high catalytic performance toward the reduction of hydrogen peroxide (H₂O₂) were reduced onto amino-functionalized fullerene (n-C₆₀-PdPt) and significantly amplified the electrochemical signal recorded by the amperometric i-t curve. Furthermore, staphylococcus protein A (SPA) with antibody orientation function was introduced to improve the immunoreaction efficiency. Accordingly, a label-free immunosensor was fabricated based on n-C₆₀-PdPt/N-GNRs for the quick detection of PCSK9. Meanwhile, to realize ultrasensitive detection of PCSK9, Pt-poly (methylene blue) (Pt-PMB) nanocomposites synthesized by a one-pot method for the first time were used as a novel signal label, which exhibited uniform morphology as well as good conductivity and produced an electrochemical signal recorded by differential pulse voltammetry (DPV). Herein, a novel sandwich-type immunosensor was designed using n-C₆₀-PdPt/N-GNRs as the sensing matrix and Pt-PMB as the signal label for sensitive detection of PCSK9. Under optimal conditions, the label-free immunosensor showed a linear range of 10pgmL^-1 to 100ngmL ^-1 with a detection limit of 3.33pgmL^-1 (S/N=3), and the sandwich-type immunosensor exhibited a linear range of 100 fg mL^-1 to 100ngmL ^-1 with a detection limit of 0.033pgmL^-1 (S/N=3) for PCSK9 detection, indicating its potential application in clinical bioassay analysis.