Nanochannel-confined Ni(OH)2-CeO2 composite nanozyme boosts electrochemiluminescence of luminol-dissolved oxygen for immunosensing

Abstract

An immunosensing platform was developed based on the enhanced electrochemiluminescence (ECL) of luminol-dissolved oxygen (O₂) by nanochannel-confined Ni(OH)₂-CeO₂ composite nanozyme, which is able to sensitively detect cytokine. The mesoporous silica nanochannel array film (SNF), decorated on a cost-effective ITO electrode, features ultrasmall (2∼3 nm) nanochannels, enabling the confinement of in situ synthesized Ni(OH)₂-CeO₂ composite nanozyme via a continuous electrodeposition process. Ni(OH)₂-CeO₂ exhibits dual peroxidase (POD) and oxidase (OXD) enzyme-like activities, serving as an efficient oxygen reduction reaction (ORR) catalyst to produce reactive oxygen species (ROS) and catalyze luminol oxidation. Compared to nanozymes synthesized on flat electrodes, nanochannel-confined nanozyme demonstrates superior ECL enhancement. The combination of Ni(OH)₂ and CeO₂ exhibits strong synergistic catalytic performance, boosting ECL of luminol-O₂ under neutral conditions by 33.7 orders compared to electrode without confined nanozyme. Using tumor necrosis factor-alpha (TNF-α) as a proof-of-concept demonstration, immunosensor is fabricated by immobilization recognition antibodies on the SNF outer surface. TNF-α binding induces immunocomplex formation, reducing ECL signal by increasing interfacial resistance and hindering luminol diffuse. This enables sensitive TNF-α detection over a wide linear range (10 fg/mL to 10 ng/mL) with an ultralow detection limit of 8 fg/mL. The immunosensor demonstrates good selectivity, stability, and reproducibility.

Keywords: Composite nanozyme; Cytokine detection; Electrochemiluminescence immunosensor; Luminol-dissolved oxygen; Nanochannel confinement.