A label-free fluorescence strategy for analysis of aflatoxin M1 by self-protected DNAzyme and aptamer recognition triggered DNA walker cascade amplification

Monitoring the information of aflatoxin M1 (AFM1) is of great significance for food safety since its widespread presence in milk and other dairy products. In view of this, we developed a label-free fluorescence DNA walker based on self-protected DNAzyme for determination of AFM1. By inserting the AFM1 aptamer into DNAzyme, the complete DNAzyme was split into two separated parts and designed to be an arch-like shield to avoid its degradation in complex matrix. This excellent structure of DNAzyme and the report probe were pre-assembled on the surface of gold nanoparticles (AuNPs). Through the high efficiency affinity between AFM1 and its aptamer, the DNAzyme could be activated and show its high catalytic cleavage towards its substrate of report probe. The releasing G-quardruplex (G4) of this report probe from AuNPs could combine with berberine and exhibit obvious fluorescence values. Under optimized experimental conditions, the AFM1 detection limit was achieved at 6.40 ng/L. This DNA walker exhibited good selectivity, reproductivity and stability. Furthermore, the feasibility for analysis in real sample of our method was performed towards the target spiked in milk, indicating its potential application for real sample determination.