A fluorescence and colorimetric dual-mode aptasensor for kanamycin detection

This study presents the development of a dual-mode aptasensor for the sensitive detection of kanamycin (KAN), utilizing both fluorescence and colorimetric signals. The aptasensor was constructed using amino-functionalized silica nanoparticles (SiO₂) combined with copper nanoclusters (CuNCs) and DNA-templated silver nanoclusters (DNA-AgNCs). Encapsulating CuNCs within SiO₂ (CuNCs@SiO₂) enhanced their stability by shielding them from environmental interference, while maintaining their bright blue fluorescence as a reference signal. DNA-AgNCs, which contain a KAN-recognizing aptamer and emit red fluorescence, served as the response signal. Single-stranded DNA was conjugated to CuNCs@SiO₂ through a reaction between amino and carboxyl groups, and AgNCs were synthesized using the single-stranded DNA as a template. In the absence of KAN, the aptamer fragments in the DNA-AgNCs bound to gold-palladium nanoparticles (Au@PdNPs), resulting in fluorescence resonance energy transfer (FRET) and quenching of the fluorescence of DNA-AgNCs. When KAN bound to the aptamers, this disrupted the FRET, leading to fluorescence recovery. Increasing KAN concentration led to the higher fluorescence intensity of DNA-AgNCs, with a visible color change from blue to red under ultraviolet light. A WeChat mini program was developed to rapidly detect KAN by analyzing the relationship between RGB values and KAN concentration. The ratiometric fluorescence and colorimetric modes of the aptasensor exhibited low detection limits of 7.3 nM and 14.5 nM, respectively. The aptasensor was successfully applied to detect KAN in food samples. This aptasensor, combined with a smartphone, offers high practical utility for sensitive KAN detection.