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

Abstract

A solid-state electrochemiluminescence (ECL) switch biosensor using a Ru(bpy)₃²⁺/β-cyclodextrin–Pd nanoparticles (β-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)₃²⁺/β-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)₃²⁺. Meantime, the hairpin-like Fer-DNA probe acted as the ECL signal switch, which was designed by a molecular recognition strategy and attached to β-CY–PdNPs through host–guest interactions between β-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)₃²⁺ 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)₃²⁺ 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.