Electrochemiluminescence ratio sensor for detecting MCP-1 based on s-PdNS

This study proposes a novel sandwich-based ratio electrochemiluminescence (ECL) immunosensor for detecting monocyte chemotactic protein-1 (MCP-1), a marker of cardiovascular disease. We synthesized sulfur-doped palladium nanosheets (S-PdNS), which possess a stable structure and uniform morphology, and can quench signals generated by the S₂O₈²⁻/O₂ ECL system. Using glutaraldehyde (GA), we conjugated luminol to these nanosheets and combined them with a secondary antibody. This modification enabled the nanomaterial to produce a new luminol signal as an internal reference for detection while quenching the S₂O₈²⁻/O₂ ECL signal. To date, no studies have utilized both mechanisms for detection. Furthermore, the deposition of gold nanoparticles (AuNPs) on the surface of the glassy carbon electrode (GCE) allowed for increased antibody binding and improved electron transmission in the ECL system. When trace analytes are present, the S₂O₈²⁻/O₂ ECL signal decreases, and the luminol ECL signal increases. This setup allowed us to obtain two signals from one measurement and use the ratio to construct a standard curve, significantly reducing the possibility of misjudgment. Under optimal conditions, the linear detection range for MCP-1 is 10^–2.5 pg mL⁻¹ to 10³ pg mL⁻¹, with a detection limit of 1.6 fg mL⁻¹ (S / N = 3). The immunosensor also exhibited excellent selectivity, repeatability, and stability, expanding the application of the dual luminescence mechanism and providing an effective method for early monitoring of cardiovascular disease.