Highly sensitive electrochemical aptasensor for ochratoxin A detection in barley flour: a novel nanocomposite approach with RGO-Cu-Ni-BTC-MOF and hematoxylin.

An electrochemical aptasensor is presented. It is designed for the detection of ochratoxin A (OTA), employing a nanocomposite of reduced graphene oxide (RGO) and a bimetallic copper-nickel 1,3,5-benzene tricarboxylate metal-organic framework (Cu-Ni-BTC-MOF) to achieve enhanced signal amplification. Additionally, hematoxylin was used as an electroactive label to facilitate the generation of the electrochemical signal. The OTA-specific aptamer was immobilized onto the RGO-Cu-Ni-BTC-MOF and subsequently hybridized with its complementary DNA (cDNA). Hematoxylin was intercalated within the resulting aptamer-cDNA duplex. The analytical signal was determined as the difference in the electrochemical responses of accumulated hematoxylin before and after incubation with OTA. Differential pulse voltammetry (DPV) was employed for quantitative determination, revealing a linear detection range of 1.0 fg mL-1 to 300.0 ng mL-1, with a detection limit of 4.6 × 10-1 fg mL-1. The fabricated aptasensor successfully quantified OTA in a real barley flour sample, demonstrating high sensitivity, selectivity, and practical applicability in food safety monitoring.