A colorimetric and electrochemical dual-modal ochratoxin a aptasensor based on branched hybridization chain reaction signal amplification.

Ochratoxin A (OTA), a fungal toxin, induces various toxic effects in animals and humans through the enrichment of toxin residues. In this work, a dual-modal biosensor based on gold nanoparticles (AuNPs) and branched hybridization chain reaction (bHCR) was proposed for the detection of OTA. The strategy is contingent on OTA aptamer-bridged occurrence of bHCR and the salt-induced aggregation of AuNPs. OTA-apt/cDNA could be used to specifically identify the OTA and trigger bHCR reactions, producing a long-branched dsDNA polymer. The electroactive molecule-methylene blue (MB) can be inserted into the superstructure of branched DNA due to the formation of DNA polymers, leading to dynamic changes in MB redox signaling. The residual DNA hairpins were added and adhered to the surface of AuNPs, but they were inadequate to prevent the AuNPs from salt-induced aggregation. The dual-modal yields limits of detection of 4.8 pM (electrochemical assay) and 0.25 nM (colorimetric assay), respectively. It exhibited excellent specificity against common mycotoxins (AFB1, DON, FB1, ZEN), with satisfactory recoveries in corn flour (92.9-108.3 %). This aptasensor, which adopts a dual-modal strategy, features self-calibration to reduce false-positive results and improve accuracy. It demonstrates significant advantages in mycotoxin detection.