Gold-silver-platinum trimetallic nanozyme-based dual-mode immunosensor for ultrasensitive osteoprotegerin detection

In this study, we report a novel gold-silver-platinum nanocomposite (AuNP-AgNP-PtNP), which displayed excellent peroxidase-mimicking activity because of the synergistic effect involving three metals. The nanozyme allowed the development of a sensitive and specific dual-mode immunodetection system to detect protein using electrochemical and colourimetric assays. The developed ultrasensitive dual-mode immunosensor was based on the anti-osteoprotegerin antibody-linked nanozyme interaction with recombinant osteoprotegerin (rOPG) protein coated over a microtiter plate. Based on the excellent electrocatalytic activity of the trimetallic nanozyme towards reducing hydrogen peroxide (H2O2), the trimetallic nanozyme could be employed towards electrochemical immunodetection of the rOPG proteins. The proposed dual-mode biosensor allowed enhanced sensitive determination of rOPG proteins with a wide linear range of 0.1 fg/mL to 10 ng/mL for electrochemical detection and 1 fg/mL to 100 ng/mL for colourimetrically detecting rOPG proteins. Moreover, the dual-mode sensor could detect rOPG proteins with a LOD of 1.81 pg/mL using the electrochemical mode and 1.87 pg/mL using the colourimetric detection mode. Moreover, the study demonstrates outstanding selectivity, sensitivity, and specificity, yielding robust recoveries in human serum samples.