Porous Fe/CeO2 Nanozyme-Based Hydrogel Colorimetric Platform for on-Site Detection of Kanamycin

Excessive use of antibiotics causes their residues in the environment and food, seriously threatening ecosystem and human health. Designing a portable and sensitive sensor for on-site analysis of antibiotics is therefore in high demand. In this study, we have developed a smartphone-capable hydrogel colorimetric platform for ultrasensitive detection of kanamycin (KAN) based on aptamer-regulated nanozyme activity. The synthesized Fe/CeO2 hexagonal bipyramidal microcrystals (Fe/CeO2 HBs) exhibited excellent peroxidase-like activity, but it could be obviously inhibited by the aptamer, and the inhibition effect was further enhanced with the specific recognition between target and aptamer, making it possible to design a facile colorimetric method for KAN analysis. Moreover, the aptamer-functionalized Fe/CeO2 HBs (Fe/CeO2 HBs@Apt) were introduced into the hydrogel to fabricate a portable analytical tube, whose colorimetric signal was read out by a smartphone platform, realizing the on-site analysis of KAN. The linear response range was 0.05–48.45 ng mL–1 with an ultralow detection limit of 0.035 ng mL–1 and the recovery rate ranging from 99.57 to 103.76% for spiked real samples, demonstrating its superior accuracy and reliability. This work provides new insights into designing the solid-phase hydrogel-based colorimetric method for on-site analysis of antibiotic residues.