Magnetic capture of sulfur quantum dots encapsulated in MOF-5-NH2 via a target-driven self-cycling catalyzed hairpin assembly for the sensitive detection of patulin

Tools to detect low molecular weight mycotoxin patulin (PAT) are urgently needed because of its harm to human health. Here, we report a simple, effective, and sensitive fluorescent aptasensor based on sulfur quantum dots encapsulated in MOF-5-NH2 (SQDs@MOF-5-NH2) and self-cycling catalyzed hairpin assembly (scCHA) for the detection of PAT in apple juice. The SQDs@MOF-5-NH2 synthesized by a "bottle-around-ship " solvothermal method works as a fluorescent probe and offers enhanced fluorescence intensity and good water-solubility versus MOF-5-NH2 due to the encapsulation of water-soluble SQDs. Meanwhile, the scCHA designed by the two DNA hairpins is initiated after the formation of PAT/aptamer, which further recycles PAT to effectively capture multiple fluorescence probes (SQDs@MOF-5-NH2) and amplify the detection signal. Attributed to the synergistic effect between the strong fluorescence intensity of SQDs@MOF-5-NH2 and the efficient PAT utilization of scCHA, the fluorescent aptasensor exhibits high sensitivity with detection limits as low as 0.753 pg/mL. The system has satisfactory specificity, anti-interference, and reproducibility (RSDs of intra-assay and inter-assay were 3.24% and 8.60%, respectively). The recoveries in apple juice were between 89.03% and 107.67%, which were with good consistency versus high-performance liquid chromatography (HPLC). These data collectively show that the developed fluorescent aptasensor has a good practical application value.