Photoelectrochemical aptasensor for kanamycin determination based on exonuclease I-assisted target signal amplification and photoexcited electron transfer strategy

[Display omitted] •Effective assembly of β-glucosidase with the design of capture DNA and hairpin DNA.•Recovery of photocurrent of TNA/g-C3N4 due to catalytic hydrolysis of β-glucosidase.•Sensitive PEC aptasensing for kanamycin with Exo I-assisted recycling amplification. In the present work, graphitic carbon nitride (g-C3N4) was generated in situ on the TiO2 nanotube arrays (TNAs) to form TNA/g-C3N4, the capture DNA (c-DNA) was immobilized on the TNA/g-C3N4 and the anti-kanamycin aptamer was assembled by the complementary base pairing to construct a TNA/g-C3N4/c-DNA-apatmer photoelectrochemical (PEC) aptasensor for kanamycin determination, which had obvious visible-light photocurrent response, and the photocurrent would decrease when immersing the aptasensor in Cu(II) solution due to the photoexcited electron transfer from g-C3N4 to Cu(II). In the presence of kanamycin, the anti-kanamycin aptamer left and more β-glucosidase labeled at 3′-end of hairpin DNA was assembled on the TNA/g-C3N4 with the assistance of recycling cleavage of exonuclease I (Exo I) to single-stranded aptamer. Because of the catalytic hydrolysis of linolenin by β-glucosidase, the released cyanide ion coordinated with Cu(II), hindering the photoexcited electron transfer from g-C3N4 to Cu (II), and leading to the increase of photocurrent. Therefore, a simple, rapid and sensitive PEC aptasensor was constructed for kanamycin determination with good reproducibility and stability based on the Exo I-assisted target recycling signal amplification and photoexcited electron transfer strategy, in which the increased photocurrent value of the aptasensor was linear with the concentration of kanamycin in the range of 0.1–150 nM, and the limit of detection was 0.03 nM with the signal-to-noise ratio of 3, which has been successfully applied for the real food sample analysis with good precision of RSD less than 5.6% and good accuracy of the recoveries ranged from 90% to 120%.