Aptamer-regulated silver core-cuprous oxide shell nanozyme for surface-enhanced raman scattering and colorimetric dual-mode detection of kanamycin in food

This work developed a dual-mode sensor based on aptamer regulation of silver core-cuprous oxide shell (Ag@Cu 2 O) nanozyme activity for kanamycin detection. The synthesized Ag@Cu 2 O nanoparticles served as both a surface-enhanced Raman scattering activity (SERS) substrate and a peroxidase-like catalytic activity. The aptamer adsorbed on the Ag@Cu 2 O surface enhanced the nanozyme activity through electrostatic interactions with positively charged 3,3′,5,5′-tetramethylbenzidine (TMB). This promoted the oxidation of TMB to blue oxidized 3,3′,5,5′-tetramethylbenzidine (ox-TMB) by hydrogen peroxide (H 2 O 2 ). Upon kanamycin binding, the colorimetric absorbance and SERS intensity decreased. The SERS mode achieved a linear range of 0.01–1 μM and the limit of detection (LOD) of 1.78 nM. The colorimetric mode provided a linear range of 0.1–1 μM and a LOD of 47.7 nM. Good recoveries (92.48–102.57%) and low relative standard deviations (RSD < 5.0%) were achieved in spiked honey and mutton samples. This dual-mode design offered potential for food safety monitoring of kanamycin residues.