CuIn2S4 nanozymes with engineered peroxidase-like activity enable robust sweat glucose monitoring via hierarchical design

Nanozymes, while promising as next-generation biocatalysts, face translational challenges such as insufficient atomic synergy, environmental interference, and spectral mismatches in portable biosensing. To address these limitations, we developed a CuIn 2 S 4 nanozyme with an “atomic-mesoscopic-macroscopic” hierarchical design, achieving robust sweat glucose monitoring through synergistic mechanisms. Leveraging the AB 2 X 4 crystal framework, we engineered C In bimetallic coordination with d-p orbital hybridization, creating localized charge-enriched regions that reduced the adsorption energy barrier of H 2 O 2 ( ΔE  = −1.51 eV, bond elongation 0.03 Å), yielded preferable peroxidase-like (POD-like) activity ( V max  = 9.63 × 10 −8  M·s −1 ), with hydroxyl radical (·OH) generation confirmed by EPR spectroscopy. To mitigate signal drift caused by dynamic sweat conditions (pH 4.5–7.0, ionic strength 0.12–0.18 M), we employed response surface methodology integrating Plackett-Burman screening and central composite design. This approach resolved nonlinear pH-ionic strength coupling (X 1  ×  X 6 : β  = −0.044) under simulated sweat environments (pH 5.5, 0.3 M NaCl). Building on these advancements, we designed a thermo-responsive F127@GOx@CuIn 2 S 4 hydrogel platform. Its sol-gel phase transition (critical temperature: 23.5 °C) spatially confined glucose oxidation cascades: GOx-mediated H 2 O 2 production triggered ·OH-driven chromogenic reactions using o -phenylenediamine (OPD) or 4-aminoantipyrine (4-AMAP) as indicator. A smartphone-based RGB analysis optimized for the blue channel ( R 2  = 0.97) enabled precise classification of sweat glucose levels into normal, prediabetic, and diabetic ranges. This study establishes a hierarchical multi-scale engineering framework - spanning atomic design, mesoscale regulation, and macroscopic application - to advance nanozyme applications in non-invasive diagnostics. Our work provides a blueprint for real-time metabolic monitoring through synergistic material innovation and portable detection technologies.