Dual-ratiometric fluorescent aptasensor based on gold nanoclusters and dual-amplification strategy for simultaneous detection of ochratoxin A and aflatoxin B1

Abstract

In this study, two kinds of gold nanoclusters (AuNCs) with fluorescent properties were synthesized as internal reference signals, while the label-free fluorescent dyes N-methylporphyrin dipropionate IX (NMM) and SYBR Green I (SGI) were used as the response signals. Dual ratiometric fluorescent aptasensor was established for the simultaneous detection of ochratoxin A (OTA) and aflatoxin B1 (AFB₁). The aptamer and complementary strands of two targets can self-assemble to form Y-shaped DNA nanostructures. When the target was present, the target can specifically bind to its aptamer and release complementary DNA. The complementary DNA can be used as an initiator strand to trigger the amplification reaction of hybridization chain reaction (HCR) and catalytic hairpin assembly (CHA). Fluorescent signals were then produced by the addition of SGI and NMM. The ratio of the fluorescent signals generated by SGI and NMM to the fluorescent signals generated by the two AuNCs can be used to quantitatively detect OTA and AFB₁. The dual ratiometric fluorescent aptasensor has good specificity and accuracy. Under optimal experimental conditions, the linear ranges of OTA and AFB₁ were 0.05–200 ng/mL, and the detection limits were 6.7 pg/mL and 8.6 pg/mL, respectively. The developed aptasensor was successfully applied to detect mycotoxins in real samples, confirming the favorable practicality.