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 ...