An electrochemiluminescence biosensing platform for Hg2+ determination based on host-guest interactions between β-cyclodextrin functionalized Pd nanoparticles and ferrocene

A solid-state electrochemiluminescence (ECL) switch biosensor using a Ru(bpy)(3)(2+)/beta-cyclodextrin-Pd nanoparticles (beta-CY-PdNPs)/gelatin (Gel) complex and a ferrocene-labeled DNA probe (Fer-DNA) for the detection of Hg2+ was successfully developed. The ECL biosensor includes an ECL substrate and an ECL signal switch. The Ru(bpy)(3)(2+)/beta-CY-PdNPs/Gel composite modified on a glassy carbon electrode was used as the ECL substrate, which could bring about a clear and stable ECL signal by Ru(bpy)(3)(2+). Meantime, the hairpin-like Fer-DNA probe acted as the ECL signal switch, which was designed by a molecular recognition strategy and attached to beta-CY-PdNPs through host-guest interactions between beta-CY and ferrocene. Our investigation indicated that, when Hg2+ was absent, the Fer-DNA probe retained its hairpin structure and led to an obvious quenching effect of the Ru(bpy)(3)(2+) signal. However, when the biosensor was incubated with Hg2+, the specific T-Hg2+-T interaction brought about a change of the Fer-DNA conformation, and such conformation adjustment resulted in a clear signal recovery of Ru(bpy)(3)(2+) owing to the reduced quenching effect of ferrocene. The ECL switch biosensor offered good linear responses for Hg2+ in the range of 0.003-600 ng mL(-1)with a detection limit of 0.0015 ng mL(- 1) at the 3s(blank) level.