Chitosan and nafion assisted modification of enzyme-free electrochemical immunosensors for the detection of tetrodotoxin

Tetrodotoxin (TTX) is one of the most toxic nonprotein marine neurotoxins without antidotes. Two enzyme-free electrochemical immunosensor for the detection of TTX are fabricated in this work. On this immunosensor, a competitive immunoassay is established. Chitosan and Nafion are used to facilitate the TTX antigen modification, where TTX antigen is attached to gold nanoparticles (AuNPs) to perform good electrochemical measurement. The detection strategy involves an enzyme-free process when performing electrochemical immunoassay. The LOQ of 4 µg/kg for real samples and the linear range from 2 to 1250 ng/mL for solution test are obtained. Recovery of >78% and relative standard deviation of <6.1% for the two immunosensors are further validated by spiking experiment. Test on pufferfish samples shows consistency with the results from the HPLC-MS method. These electrochemical immunosensors have the merits of being portable, low cost, battery-powered and fast for practical application, which can be a promising alternative to ELISA for on-site detection.