Rational design of a Cu-based laccase-like nanozyme for catalytic oxidation and detection of phenolic compounds

Developing robust, highly efficient nanozymes as laccase alternatives for the catalytic oxidation and detection of phenolic pollutants is of paramount importance for the ecological environmental sustainability. In this study, we design and fabricate a novel laccase-like Cu-ImSH nanozyme via the solvothermal coordination between Cu(II) ions and a biomimetic 2-mercaptoimidazole (ImSH) organic ligand. By virtue of the resultant Cu I −S and Cu II −N catalytic sites as well as favorable surface properties, the nanozyme exhibits an over 10-fold enhancement in specific activity compared with natural laccase, along with proven catalytic robustness and satisfactory reusability. In terms of environmental applications, the nanozyme is successfully deployed for the catalytic oxidation of diverse phenolic compounds (PCs) and the colorimetric detection of 2,4-dichlorophenol (2,4-DP) as a model pollutant, achieving a detection limit (LOD) of 0.12 μM. Meanwhile, its biomedical potential is demonstrated by the sensitive colorimetric assay of epinephrine (EP) as a model biomarker, with an LOD as low as 0.43 μM. Furthermore, the superior adaptability of Cu-ImSH enables the construction of a hydrogel-based multifunctional point-of-care testing (POCT) kit, which achieves facile, instrument-free determination of both 2,4-DP and EP with reliable detection performance. Taken together, by deepening the understanding of the structure-activity relationship of natural laccase, this work provides considerable value in guiding the biomimetic design of high-performance nanozymes. Moreover, the exceptional, robust, and adaptable catalytic activity of the as-prepared Cu-ImSH nanozyme holds substantial promise for widespread, multi-scenario applications.