An ultrasensitive label-free photoelectrochemical aptasensor based on terminal deoxynucleotidyl transferase amplification and catalytic reaction of G-quadruplex/hemin.

An ultrasensitive photoelectrochemical (PEC) analysis method based on terminal deoxynucleotidyl transferase (TdT) amplification effect and G-quadruplex/hemin (G4/hemin) catalytic reaction assisted signal amplification was prepared for the determination of ampicillin. A novel Au NPs@SnIn 4 S 8 -graphene sensitized structure was used as photoactive material to attain an intense basic photocurrent. In the presence of the target, P1 obtained by strand displacement reaction was introduced into the electrode surface, and abundant G4/hemin was formed in the presence of TdT and hemin. Subsequently, G4/hemin with horseradish peroxidase-mimicking activity catalyzed the oxidation of 4-chloro-1-naphthol by H 2 O 2 to form benzo-4-chlorohexadienone precipitation on the modified electrode surface, which severely hindered the electron transfer and effectively inhibited the photocurrent output. The detection range of the PEC aptasensor for ampicillin was 10 fM-30 nM, and the limit of detection was 4.97 fM. The aptasensor had good stability and high sensitivity, and possessed a promising application in biological analysis and environmental monitoring. [Display omitted] • A label-free, highly sensitive photoelectrochemical aptasensor for ampicillin detection was proposed. • The introduction of the signal amplification strategy on TdT terminal extension and mimetic enzymatic catalytic precipitation achieved high sensitivity assay. • The aptasensor possesses a promising application in biological analysis and environmental monitoring. [ABSTRACT FROM AUTHOR]