Ammonia-Etched Laccase-Mimicking Nanofiber-like Enzyme with Fluorescent Properties for the Detection of Oxytetracyclin

A nanofiber-like enzyme, e-Cu-BN, was synthesized, exhibiting enhanced laccase-like activity compared to Cu-BN without ammonia etching. This study utilized the laccase-like activity and fluorescent properties of e-Cu-BN to develop a dual-mode fluorescence-colorimetric sensor for the detection of oxytetracycline (OTC). Specifically, e-Cu-BN catalyzes the oxidation of 2,4-dichlorophenol (2,4-DP), resulting in the formation of red quinone imine dye (QI) in conjunction with 4-aminophenol (4-AP), which exhibits strong UV absorption at 510 nm, while the OTC inhibits this reaction. Meanwhile, the fluorescence intensity of e-Cu-BN decreases as the concentration of OTC increases. Utilizing the two signal changes, we successfully achieved the detection of OTC. In addition, a smartphone-assisted hydrogel-based simple sensing platform was designed. The real-time detection of OTC was realized by the smartphone RGB value analysis software, and we added logic gates to simplify the detection process. This approach offers a rapid and cost-effective solution for OTC detection. This study not only developed a dual-mode sensor for OTC detection but also provided insights for further research into multifunctional nanozymes.