Boosted electrochemiluminescence of luminol/oxygen by nanochannel-confined nanocatalyst for sensitive aptasensing of tumor biomarker

A highly sensitive electrochemiluminescence (ECL) aptasensor was developed for the detection of carcinoembryonic antigen (CEA), a well-established broad-spectrum tumor biomarker, through the integration of nanochannel-confined nanocatalysts, endogenous coreactants, and nanochannels with anti-fouling ability. A silica nanochannel film (SNF) with uniform pore size (2–3 nm) was grown on an indium tin oxide (ITO) electrode via simple Stöber solution growth method. Nitrogen-doped graphene quantum dots (N-GQDs) were subsequently confined within the nanochannels through electrophoretic deposition. The spatial confinement significantly enhanced the catalytic activity of N-GQDs toward luminol oxidation and dissolved oxygen (DO) reduction, thereby significantly amplifying the ECL signal without the need for additional coreactants. The outer surface of SNF was functionalized with epoxy groups using a silane coupling agent, allowing for covalent immobilization of the CEA-specific aptamer to construct a selective recognition interface. Upon target binding, steric hindrance and increased interfacial resistance hindered luminol diffusion and electron transfer, resulting in ECL signal suppression. Under optimized conditions, the constructed aptasensor exhibited a linear response toward CEA in the range of 0.001–10 ng/mL with a detection limit of 0.4 pg/mL (S/N = 3). The combined use of endogenous O₂ as a coreactant and the anti-fouling properties of the SNF enabled direct and reliable detection of CEA in complex serum samples without the need for complicated pretreatment. This work presents a versatile sensing platform based on nanoconfinement, catalyst enhancement, and antifouling interfaces for sensitive clinical biomarker detection.