Electrochemiluminescence immunosensor based on carbon nanotube interface-enhanced porphyrin hydrogel for Staphylococcus aureus detection

Porous porphyrin hydrogel (SCT hydrogel) showed stable ECL performance via spatial-confined effect. • The interface effect between CNTs and the SCT hydrogel led to the ECL enhancement. • A label-free ECL immunosensor was constructed for S. aureus detection based on CNTs and SCT hydrogel. • This ECL immunosensor enabled rapid and ultrasensitive detection of S. aureus in milk, water, and pork samples. Functionalized hydrogel-based electrochemiluminescence (ECL) devices still face the challenges of insufficient luminescence efficiency and sensing interface modification. Herein, we propose the carbon nanotubes (CNTs)-boosted porphyrin hydrogel ECL sensing strategy. The three-dimensional porous porphyrin hydrogels (SCT hydrogels) are composed of a dual-crosslinked sodium alginate (SA) and chitosan (CS) network encapsulating a water-soluble ECL luminophore (5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrin, TPPS). The spatial-confinement effect significantly enhanced the ECL stability of TPPS, as confirmed by finite element analysis. Furthermore, four types of CNTs are separately employed as sensing scaffolds to reduce the electrical resistance of hydrogel. Notably, carboxylated CNTs provide greater ECL enhancement than non-carboxylated ones, with carboxylated multi-walled CNTs (MWCNTs-COOH) yielding the best improvement (1.87-fold that of the SCT hydrogel alone). Interestingly, the interface effect between CNTs and SCT hydrogel contributes to a higher ECL enhancement than their mutual doping. Electrochemical techniques, ECL methods, and density functional theory systematically reveal the improvement mechanism of CNTs. Furthermore, the MWCNTs-COOH-assisted SCT hydrogel is used to construct a label-free and highly sensitive ECL immunosensor for Staphylococcus aureus detection. By establishing CNTs as a pivotal promoter, this work opens the potential of flexible hydrogel-based ECL sensors for rapid and sensitive foodborne pathogen detection. A label-free ECL immunosensor for Staphylococcus aureus achieves outstanding performance, driven by the spatial-confined effect of a porous porphyrin hydrogel and the interface effect between CNTs and the SCT hydrogel. Download: Download high-res image (360KB) Download: Download full-size image