Colorimetric aptasensor for tobramycin based on a highly stabilized aptamer-enhanced enzyme-mimicking activity of iron oxide/graphene oxide nanospheres.

Antibiotic contaminants in food are associated with detrimental health issues, and thus, the design of rapid and reliable detection methods to monitor them is in high demand. Although colorimetric aptamer sensing methods can achieve accurate and quick visual read-out analysis, they still have morphological defects that affect the detection efficiency and stability of the aptasensor. Hence, a simple and highly selective iron oxide/graphene oxide (Fe3O4/GO) nanospheres was developed and modified with an aptamer as nanozymes for colorimetric detection of tobramycin (Tob). Due to the electrostatic and π-π stacking interaction between the aptamer and the spherical Fe3O4/GOs nanozyme, the catalytic activity of the nanozyme was enhanced by the robust affinity between the aptamer and the 3,3',5,5'-tetramethylbenzidine (TMB) substrate. However, the presence of Tob could obstruct the catalytic activity through the specific binding of aptamer to Tob and the detachment of aptamer from the surface of the Fe3O4/GO, causing a low catalytic activity. Based on this strategy, a visual and quantitative detection for Tob was achieved with a detection limit of 70.7 nM. The proposed aptasensor demonstrated high selectivity, ease of operation, and potential application in food samples with satisfactory recoveries of 98.4-108.5 %. Therefore, this proposed method has great prospects for monitoring food safety and could be applied for sensing varied antibiotics by just switching the target-specific aptamer.