A smartphone-based nanoenzyme-modulated aptasensor using an infrared camera for rapid detection of kanamycin

The detection of antibiotics in water is crucial to ensure the safety of drinking water and prevent the spread of antibiotic resistance in the environment. In this study, we present a novel strategy for the selective and sensitive detection of kanamycin (KAN) in water by combining infrared thermography with aptamer detection technology. The aptamers specific to KAN were immobilized on the surface of gold nanoparticles (AuNPs), thereby enhancing the catalytic activity of AuNPs in the 3,3′,5,5′-tetramethylbenzidine (TMB)-hydrogen peroxide system to produce oxidized TMB with photothermal conversion capability. KAN competitively binds to the aptamer and modulates the catalytic capacity of the AuNPs surface, resulting in different photothermal conversion capacities of the final solution. Under near-infrared laser irradiation, the target KAN concentration is converted into a measurable thermal signal. To fabricate a portable sensing setup, we integrated the device with a smartphone. The aptasensor can selectively detect KAN with a limit of detection of 1.55 ng·mL⁻¹ and a limit of quantification of 13.62 ng·mL⁻¹. The detection time of our sensor is real time with a reaction time of 30 min. It demonstrates excellent stability and recoveries ranging from 96.9 % to 106.1 % for practical water samples. This portable aptasensor offers rapid detection, simplicity, and affordability, enabling real-time analysis of antibiotic residues in water.