Sensitive electrochemical detection of oxytetracycline based on target triggered CHA and poly adenine assisted probe immobilization

Highlights: • CHA and signal amplification were triggered by target. • The transformation process between the target and the Fc labeled mimic target was accomplished in homogeneous system. • Mimic targets were self-assembled on the electrode surface by poly adenine to generate electrochemical signal. Here, we developed a homogeneous electrochemical biosensor for the sensitive determination of antibiotic by the CHA reaction and the consecutive adenine mediated probe fixation. The binding of target to the target recognition sequences in the triple-helix DNA can release the trigger. It can initiate the catalytic hairpin assembly (CHA) to generate lots of mimic targets, which were labeled with electroactive substance ferrocene (Fc). Because the generated mimic target has consecutive sequence of adenines (PolyA), they can be self-assembled on the AuNPs modified electrode and finally realize electrochemical detection. Under optimal conditions, this developed biosensor achieved a satisfactory limit of detection of 0.089 nM (S/N = 3) and a linear range from 0.1 nM to 100 nM for sensitive detection of oxytetracycline with good specificity. The whole process is carried out in homogeneous solution, not only realizes signal amplification, but also avoids the complex modification process of electrode surface. Compared with some reported electrochemical sensors, the method is easier to operate and has good precision.