A novel electrochemiluminescence immunosensor based on functional β-cyclodextrin-ferrocene host-guest complex with multiple signal amplification

The shortened distance between luminophor and coreactant can effectively enhance luminous efficiency in electrochemiluminescence (ECL) system owing to the improvement of electron transfer rate. Here, a novel sandwich-type ECL immunosensor based on N-(aminobutyl)-N-(ethylisoluminol) (ABEI) as luminophor was constructed by integrating hollow gold nanoparticles (HAuNPs), l-cysteine (l-Cys) and ferrocene (Fc) in a complex for multiple signal amplification. The HAuNPs with large specific surface areas and superior conductivity were first used as scaffolds to load abundant coreactant l-Cys, aiming to further assemble catalyzer Fc stably. Through host-guest recognition, the β-cyclodextrin (β-CD) functionalized ABEI thus subsequently decorated on Fc, bringing in shortened distance between luminophor ABEI and coreactant l-Cys with high ECL signal. Moreover, the catalyzer Fc and HAuNPs could dramatically promote decomposition of another coreactant H2O2 to produce abundant superoxide radical (O2ˉ) and hydroxyl radical (OH) for further signal amplification. Taking β2-microglobulin (β2 M) as model analyte, the developed immunosensor exhibited a superior performance for detection β2 M in the range of 1.0 × 10−3–1.0 × 103 ng mL−1 with a detection limit of 2.6 × 10−1 pg mL−1. The developed strategy realized solid-state ECL detection and multiple ECL signal amplification, providing a novel sensitive detection method for β2 M, which may show a great promise for the clinical application.