Dual-mode photoelectrochemical/electrochemical sensor based on Z-scheme AgBr/AgI-Ag-CNTs and aptamer structure switch for the determination of kanamycin

A signal-on dual-mode aptasensor based on photoelectrochemical (PEC) and electrochemical (EC) signals was established for kanamycin (Kana) assay by using a novel Z-scheme AgBr/AgI-Ag-CNTs composite as sensing platform, an aptamer structure switch, and K-3[Fe(CN)(6)] as photoelectron acceptor and electrochemical signal indicator. The aptamer structure switch was designed to obtain a signal-off state, which included an extended Kana aptamer (APT), one immobilized probe (P1), and one blocking probe (P2) covalently linked with graphdiyne oxide (GDYO) nanosheets. P1, P2, and aptamer formed the double helix structure, which resulted in the inhibited photocurrent intensity because of the weak conductivity of double helix layer and serious electrostatic repulsion of GDYO towards K-3[Fe(CN)(6)]. In the presence of Kana, APT specifically bound to the target and dissociated from P1 and P2, and thus, a signal-on state was initiated by releasing P2-GDYO from the platform. Based on the sensing platform and the aptamer structure switch, the dual-mode aptasensor realized the linear determination ranges of 1.0 pM-2.0 mu M with a detection limit (LOD) of 0.4 pM (for PEC method) and 10 pM-5.0 mu M with a LOD of 5 pM (for EC method). The aptasensor displayed good application potential for Kana test in real samples.

Automated summary

In this study, a dual-mode aptasensor based on photoelectrochemical and electrochemical signals was developed for the detection of kanamycin. The sensor utilized a novel Z-scheme composite as the sensing platform and an aptamer structure switch. With the help of the sensing platform and aptamer structure switch, the aptasensor exhibited a low detection limit and a wide linear detection range, making it potentially useful for kanamycin testing in real samples.