Nanoscale-enhanced Ru(bpy)32+ electrochemiluminescence labels and related aptamer-based biosensing system

Abstract

A unique multilabeling at a single-site protocol of the Ru(bpy)₃²⁺ electrochemiluminescence (ECL) system is proposed. Nanoparticles (NPs) were used as assembly substrates to enrich ECL co-reactants of Ru(bpy)₃²⁺ to construct nanoscale-enhanced ECL labels. Two different kinds of NP substrates [including semiconductor NPs (CdTe) and noble metal NPs (gold)] capped with 2-(dimethylamino)ethanethiol (DMAET) [a tertiary amine derivative which is believed to be one of the most efficient of co-reactants of the Ru(bpy)₃²⁺ system] were synthesized through a simple one-pot synthesis method in aqueous media. Although both CdTe and gold NPs realized the enrichment of ECL co-reactants, they presented entirely different ECL performances as nanoscale ECL co-reactants of Ru(bpy)₃²⁺. The different effects of these two NPs on the ECL of Ru(bpy)₃²⁺ were studied. DMAET-capped CdTe NPs showed enormous signal amplification of Ru(bpy)₃²⁺ ECL, whereas DMAET-capped gold NPs showed a slight quenching effect of the ECL signal. DMAET-capped CdTe NPs can be considered to be excellent nanoscale ECL labels of the Ru(bpy)₃²⁺ system, as even a NP solution sample of 10⁻¹⁸ M was still detectable after an electrostatic self-assembly concentration process. DMAET-capped CdTe NPs were further applied in the construction of aptamer-based biosensing system for proteins and encouraging results were obtained.