Ruthenium Poly(ethylenimine)/Gold Nanoparticles Immobilized on Dendritic Mesoporous Silica Nanoparticles for a CA15‑3 Electrochemiluminescence Immunosensor via Cu₂O@PDA Dual Quenching

The development of a specifically sensitive approach for CA15-3 detection is of great significance for the early diagnosis and treatment monitoring of breast cancer. In the present work, an electrochemiluminescence (ECL) immunosensor was constructed for the sensitive and selective detection of CA15-3 based on a dual-quenching strategy. Ru­(dcbpy)₃²⁺, poly­(ethylenimine) (PEI), and gold nanoparticles (AuNPs) were immobilized on dendritic mesoporous silica nanoparticles (DMSNs) (Ru-PEI/AuNPs@DMSNs) with high ECL efficiency due to the high loading amounts of Ru­(dcbpy)₃²⁺, the shortened electron-transfer path between the luminophore and coreactant, and the excellent conductivity and localized surface plasmon resonance effect of AuNPs. In the presence of CA15-3, a Cu₂O nanoparticles coated with poly­(dopamine) (Cu₂O@PDA) nanocomposite was introduced to the synthesized Ru-PEI/AuNPs@DMSNs through antigen–antibody interaction, resulting in a remarkable ECL quenching due to the dual quenchers of Cu₂O and PDA. Under the optimal conditions, the fabricated sensor was used to detect CA15-3 in a wide linear range of 5.0 × 10^–5–6.0 × 10² U mL^–1 with a low limit of detection of 2.4 × 10^–6 U mL^–1. The dual-quenching ECL immunosensor was successfully applied for the determination of CA15-3 in patient serum, indicating the potential applicability of the present immuosensor for the clinical determination of CA15-3 and other cancer biomarkers.