High-efficiency electrochemiluminescence of host-guest ligand-assembled gold nanoclusters preoxidated for ultrasensitive biosensing of protein

Abstract

Herein, host–guest ligand-assembled gold nanoclusters (AuNCs) with highly efficient electrochemiluminescence (ECL) as an emitter and a programable tripedal deoxyribonucleic acid (DNA) walker with a well-regulated DNA track as the signal amplifier were used to develop an ultrasensitive biosensing platform for determining soluble urokinase-type plasminogen activator receptor (suPAR) related to chronic kidney disease. Notably, the host–guest ligand-assembled AuNCs with 6-aza-2-thiothymine (ATT) as the ligand and guanidine butyric acid (Gba) as the model (Gba/ATT-AuNCs) exhibited a strong and stable ECL signal under preoxidation, 25.6 times higher than that of traditional ATT-protected AuNCs (ATT-AuNCs). This is because of the dual-enhancement ECL mechanism of the suppression of nonradiative transitions by host–guest recognition and the improvement of the electrochemical redox rate by preoxidation. Furthermore, the trace target protein suPAR could be efficiently converted into a tripedal DNA walker to walk along a well-regulated square DNA orbit with high movement efficiency and low background signal, thereby considerably improving detection sensitivity. Thus, the established ECL sensing platform achieved the ultrasensitive detection of suPAR with a linear range from 10 fg/mL to 10 ng/mL and a limit of detection of 3.15 fg/mL, whose detection sensitivity was five orders of magnitude higher than that of the gold-standard enzyme-linked immunosorbent assay with the lowest detection concentration of 1 ng/mL. This strategy provides a novel enhanced ECL mode of AuNCs for constructing a sensitive biosensing platform and is expected to be extended to the trace detection of other protein markers in human body fluids for disease diagnosis.