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 4.3 nM to 206.4 nM was obtained for insulin detection, and the limit of detection was 2.74 nM. 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.