Multimodal lab-on-a-tube detection of AFB1 based on fluorescence and nanozyme activity of DNA templated silver nanocluster: Enhanced sensitivity through G-quadruplex formation

Aflatoxin B1 (AFB1) is the potent carcinogenic toxin secreted by fungi with widespread distribution around the world as the food contaminant. In the present study, a novel strategy has been developed for sensitive detection of AFB1 based on multiplex aptamer mediated probe and ExoIII enzyme activity. Inspired by generated fluorescence signal by DNA templated silver nanocluster (AgNCs), a specific aptasensor was designed to provide efficient interaction with AFB1 and subsequent amplify the released heterostructure included G-quadruplex after Exo-assisted activity for AgNCs fabrication. This strategy triggered repeated recognition-sensing cycle, leading to output colorimetric and fluorometric response signal. The integration of G-quadruplex in released probe, amplified the intrinsic low quantum yield and fluorescence of synthesized AgNCs and also enhanced its nanozyme activity on TMB and H2O2 substrate for colorimetric detection in single tube reaction. The developed AFB1 sensing assay showed LOD of 2.5 pM in colorimetric mode and had more sensitive LOD of 8.5 fM in fluorescence analysis. Smartphone assisted assay was also applied successfully as competitive detection approach. The proposed strategy was applicable in real sample and showed reliable results. Overall, this platform takes advantages of sensitive fluorometric analysis and nanozyme assisted colorimetric method which make it promising in practical application.