An aptamer-mediated CdSe/ZnS QDs@graphene oxid composite fluorescent probe for specific detection of insulin

Abstract

Considering the superior optical properties of CdSe/ZnS quantum dots (QDs), specific recognition characteristics of aptamer and the strong fluorescence quenching properties of graphene oxide (GO), we constructed an aptamer-mediated composite fluorescent probe composed of aptamer-modified CdSe/ZnS QDs (QDs-IBA) and GO for specific detection of insulin. Under the mediation of aptamer, QDs-IBA were effectively adsorbed onto the GO surface, forming a stable QDs-IBA@GO complex through strong π-π stacking interactions. Consequently, the fluorescence of QDs-IBA was quenched through fluorescence resonance energy transfer (FRET) between QDs-IBA and GO. During incubation with QDs-IBA, insulin specifically bound with QDs-IBA to prevent interaction between QDs-IBA and GO, leading to the insufficient quenching of QDs-IBA fluorescence. The fluorescence intensity of QDs-IBA@GO probe was directly proportional to the amount of target insulin. Under the optimized conditions, a linear response ranging from 4.3nM to 206.4nM was obtained for insulin detection, and the limit of detection was 2.74nM. The established probe demonstrated its simplicity of operation and cost-effectiveness, which was used for insulin detection in injectable insulin samples and satisfactory results were obtained.