Rapid colorimetric detection of kanamycin in water using dual-mechanism enhanced AuNPs aggregation with smartphone...

Kanamycin (Kana) residues in water pose significant threats to ecosystems and human health, highlighting the need for rapid and simple on-site monitoring methods. Conventional salt-induced aggregation of gold nanoparticles (AuNPs) for colorimetric detection often suffers from limited sensitivity and poor color contrast. Herein, we report a dual-mechanism enhanced colorimetric biosensor that combines charge neutralization by positively charged Kana with charge shielding by NaCl to amplify AuNPs aggregation. This synergistic effect triggers a distinct color change from wine-red to dark blue within 3 min, enabling rapid visual and quantitative detection of Kana. The aggregation behavior of AuNPs was characterized by UV-Vis spectroscopy, transmission electron microscopy, dynamic light scattering, and Zeta potential measurements. Under optimized conditions, the sensor exhibited a linear range of 5-250 nM with a limit of detection (LOD) of 4.4 nM based on UV-Vis analysis. Smartphone-based RGB analysis achieved instrument-free quantification in the range of 0-250 nM, with an LOD of 2.3 nM. The biosensor also demonstrated excellent selectivity toward Kana against common interfering substances and was successfully applied to spiked environmental water samples, yielding recoveries of 94.69%-105.90% with RSDs below 7.34%. This work provides a rapid, sensitive, and portable platform for on-site monitoring of antibiotic contamination.