Application of Fe-CuO bimetallic oxide nanozyme-based colorimetric sensing for highly sensitive detection of...

This research establishes a competitive colorimetric detection platform for tetracycline (TC) residue analysis in milk and aqueous matrices, with implications for assessing antibiotic-derived health risks in dairy and potable water systems. According to the developed colorimetric competitive reaction model, steady-state kinetic analysis revealed that the Fe-doped CuO (Fe-CuO) nanozymes exhibit higher substrate affinity and faster reaction kinetics than conventional enzymes. The catalytic system utilized a bimetallic nanozyme composed of Fe-CuO, which exhibited enhanced catalytic performance, using 3,3',5,5'-tetramethylbenzidine (TMB) as the color-changing substrate. Acting as the recognition component, TC competitively captured hydroxyl radicals (·OH) produced during H₂O₂ activation by the Fe-CuO nanozymes, thus preventing the oxidation of TMB into its colored form (oxTMB). The observed reaction pathway aligned closely with Density Functional Theory (DFT)-predicted mechanisms, demonstrating preferential oxidation of TC by ·OH. This mechanistic insight enabled the development of an efficient competitive sensing platform. The Fe-CuO nanozyme-based sensor showed a strong linear response within the range of 1 to 1000 nM and achieved a remarkable detection limit of 0.274 nM, indicating outstanding analytical capabilities. These results highlight its significant potential for use in environmental monitoring and ensuring food safety.