Sensitive Detection of Biomarker in Gingival Crevicular Fluid Based on Enhanced Electrochemiluminescence by Nanochannel-Confined Co3O4 Nanocatalyst

The sensitive detection of inflammatory biomarkers in gingival crevicular fluid (GCF) is highly desirable for the evaluation of periodontal disease. Luminol-based electrochemiluminescence (ECL) immunosensors offer a promising approach for the fast and convenient detection of biomarkers. However, luminol’s low ECL efficiency under neutral conditions remains a challenge. This study developed an immunosensor by engineering an immunorecognition interface on the outer surface of mesoporous silica nanochannel film (SNF) and confining a Co3O4 nanocatalyst within the SNF nanochannels to improve the luminol ECL efficiency. The SNF was grown on an indium tin oxide (ITO) electrode using the simple Stöber solution growth method. A Co3O4 nanocatalyst was successfully confined within the SNF nanochannels through in situ electrodeposition, confirmed by X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The confined Co3O4 demonstrated excellent electrocatalytic activity, effectively enhancing luminol and H2O2 oxidation and boosting the ECL signal under neutral conditions. Using interleukin-6 (IL-6) as a proof-of-concept demonstration, the epoxy functionalization of the SNF outer surface enabled the covalent immobilization of capture antibodies, forming a specific immunorecognition interface. IL-6 binding induced immunocomplex formation, which reduced the ECL signal and allowed for quantitative detection. The immunosensor showed a linear detection range for IL-6 from 1 fg mL−1 to 10 ng mL−1, with a limit of detection (LOD) of 0.64 fg mL−1. It also demonstrated good selectivity and anti-interference capabilities, enabling the successful detection of IL-6 in artificial GCF samples.