Aptamer regulated peroxidase-like activity of cobalt oxyhydroxide nanosheets for colorimetric detection of kanamycin

A straightforward label-free colorimetric aptasensor utilizing the aptamer-enhanced peroxidase-like activity of cobalt oxyhydroxide (CoOOH) nanosheets has been established for kanamycin detection. In the kanamycin-free state, aptamers adsorb onto the CoOOH surface through electrostatic forces, enhancing the peroxidase-like activity of CoOOH and thereby resulting in a strong absorption signal and a yellow hue in 3,3',5,5'-tetramethylbenzidine (TMB) upon termination of the reaction with a stop solution. Conversely, upon the introduction of kanamycin, aptamers and CoOOH nanosheets compete for binding to kanamycin, resulting in a significant decrease in the number of aptamers bound to CoOOH. As a result, the activity of CoOOH diminishes, leading to a corresponding reduction in coloration and absorbance of the solution. Hence, the quantitative determination of kanamycin could be realized by analyzing the absorbance variations. Under optimal conditions, the aptasensor demonstrated high sensitivity and specificity, with a linear detection range from 500 nM to 5 µM and a detection limit as low as 54.6 nM. Moreover, the aptasensor effectively identified kanamycin in river water samples, achieving a recovery rate between 91.7% and 102.1%. This approach offers good practicability and provides a novel platform for kanamycin detection in environmental samples.