Abstract: In this study, gold nanoclusters templated with unlabeled nucleic acid aptamers were rapidly synthesized for use in combination with gold nanoparticles modified with single-stranded DNA that is partially complementary to the DNA strands of the aptamer in a novel fluorescent composite nano-biosensor for rapid detection of ochratoxin A. The stronger binding force between the target and aptamer brought about fluorescence resonance energy transfer in the Apt-AuNCs@cDNA-AuNPs sensor whose fluorescence had been quenched and consequently recovery of the lost fluorescence intensity, thereby allowing the rapid and accurate detection of ochratoxin A (OTA). The results showed that the peak value of fluorescence intensity (FI) displayed a good linear relationship with the concentration (C) of ochratoxin A within the range from 0.01 to 2.5 ng/mL, which was fitted as FI = 689.84lgC + 8 315.31, with the limit of detection (LOD) of 0.025 ng/mL at signal-to-noise ratio of 3. This new fluorescent composite biosensor has the characteristics of simple synthesis, easy operation, high sensitivity, strong selectivity, good stability and a low LOD, which is expected to provide a new idea and platform for the detection of food safety hazard factors.

Key words: aptamer; gold nanoclusters; gold nanoparticles; toxin; fluorescence resonance energy transfer; ochratoxin A