The authors describe an aptamer-based fluorescent assay for adenosine (Ade). It is based on the interaction between silver nanoparticles (AgNPs) and CdTe quantum dots (QDs). The beacon comprises a pair of aptamers, one conjugated to Fe3O4 magnetic nanoparticles, the other to AgNPs. In the presence of Ade, structural folding and sandwich association of the two attachments takes place. After magnetic separation, the associated sandwich structures are exposed to the QDs. The AgNPs in sandwich structures act as the signaling label of Ade by quenching the fluorescence of QDs (at excitation/emission wavelengths of 370/565 nm) via inner filter effect, electron transfer and trapping processes. As a result, the fluorescence of QDs drops with increasing Ade concentration. The assay has a linear response in the 0.1 nM to 30 nM Ade concentration range and a 60 pM limit of detection. The assay only takes 40 min which is the shortest among the aptamer-based methods ever reported. The method was successfully applied to the detection of Ade in spiked biological samples and satisfactory recoveries were obtained. Graphical abstract Schematic of a highly efficient and convenient adenosine (Ade) fluorometric assay. It is based on the interaction between Ag nanoparticles (NPs) and CdTe quantum dots (QDs). Ade aptamers (ABA1 and ABA2) are used as recognition unit and Fe3O4 magnetic nanoparticles act as magnetic separator. The assay exhibits superior sensitivity and speediness.
Keywords: Ag nanoparticles; Fluorescence; Inner filter effect; Lung cancer marker; Magnetic separation; Quantum dots; Quenching; Rapid detection; Sandwich structure; Urine analysis.