A molecular imprinting-switchable laccase-like nanozyme-based onsite self-calibrating assay of ethyl carbamate...

A switchable laccase-like nanozyme based on molecular imprinting polymer (MIP) had been developed for dual-mode (colorimetric/fluorescence) self-calibrating assay of ethyl carbamate (EC) residues. The oxidation of colorless o-phenylenediamine (OPD, non-fluorescence) to yellow 2,3-diaminophenazine (DAP, λ_em = 550 nm) was catalyzed using a MIP-encapsulated fluorescence nanozyme (Cu-BH@MIP, λ_em = 420 nm). Nevertheless, EC competitively occupied the molecularly imprinted cavities, inhibiting the oxidation reaction of OPD and causing changes in the colorimetric and fluorescence. On this basis, a precise dual-mode self-calibrating strategy was proposed to integrate a smartphone to develop an efficient, portable, eco-friendly, and visual analytical platform. This platform achieved linear ranges of 10.2-500.0 μg/L (colorimetric method) and 8.4-500.0 μg/L (fluorescence method), with detection limits (LOD) of 3.06 μg/L and 2.53 μg/L, respectively. This work opens a more environment-friendly, convenient, flexible, economical and prominent multimodal self-calibrating portable service for EC residues assay to ensure food safety.