Cascade signal amplification electrochemical biosensor based on AgNPs and ring opening polymerization for...

An ochratoxin A (OTA) electrochemical biosensor based on a cascade signal amplification strategy with Ag nanoparticles (AgNPs) and ring opening polymerization (ROP) was constructed. The large specific surface area of AgNPs was used to increase the loading of OTA aptamer on the electrode surface, enhancing the ability to capture OTA as a way to achieve the first signal amplification. The OTA antibody modified with polyethylenimine specifically recognizes the OTA, forming an aptamer-OTA-antibody sandwich structure. The amino group on polyethylenimine initiates the ROP reaction with α-amino acid-n-carboxylic anhydride-ferrocene (NCA-Fc) as the monomer. A large number of electrochemical signal units of ferrocene are introduced into the sensing system for a second signal amplification. By amplifying the signal twice, the sensitivity of the sensor is improved. Under the optimal conditions, the detection range of the sensor is 1 pg·mL^-1 ~ 1 μg·mL^-1, while the detection limit is as low as 117 fg·mL^-1. Moreover, the sensor has the advantages of high sensitivity, good stability and selectivity. Standard addition recovery experiment proved that the sensing system can be successfully used for the detection of OTA in four actual samples with recoveries in the range 90.0 to 113% with RSDs of 0.6 to 5.2%, providing a new idea for the pollution assessment of mycotoxins.