A novel competitive fluorescence colorimetric dual-mode immunosensor for detecting ochratoxin A based on the synergistically enhanced peroxidase-like activity of AuAg NCs-SPCN nanocomposite

The sensitive and rapid detection of Ochratoxin A in foods is particularly urgent for ensuring human security due to its larger toxicity to the body. Herein, a novel competitive fluorescence colorimetric dual-mode immunosensor for detecting Ochratoxin A based on AuAg NCs-SPCN nanocomposite was designed and constructed. The synergistic effect of SPCN and AuAg NCs dramatically improved the nanozyme activity. The fluorescence intensity was enhanced due to the aggregation luminescence effect, and a new emission peak appeared at 440 nm to form a fluorescence signal. For colorimetric, H2O2 was effectively decomposed by AuAg NCs-SPCN to form ·OH groups and oxidize 3,3',5,5'-tetramethylbenzidine to blue oxTMB. The dual-mode immunosensor showed a good linear relationship from 0.001 μg/L to 10 μg/L and the detection limits were 0.155 ng/L (fluorescence) and 0.213 ng/L (colorimetric). So, this dual-mode immunosensor would have a potential applicative prospect for sensitive detecting Ochratoxin A and other small molecules.