Janus-structured GOx-Fe/cu Nanozymes for broad-range glucose detection and Milk analysis

Glucose oxidase (GOx) is unstable under temperature/pH variations, limiting its biosensing applications. Existing nanozyme-based glucose sensors suffer from narrow detection ranges (0.2–12.0 mM) and poor stability. Herin a Janus-structured GOx-Fe/Cu nanozyme was synthesized via one-pot self-assembly with Fe₁₋ₓS and GOx partially-covered on Cu₃(PO₄)₂ nanoflowers. This nanozyme achieved an ultra-broad glucose detection range (0.5–20 mM, LOD = 34.18 μM), 40 times wider than existing nanozyme, with enhanced stability (>80% activity after 7 h at pH 3 and 5 h at 60 °C) and high specificity. When integrated into a chitosan/agarose hydrogel, it enabled visual glucose quantification through smartphone-based portable detection. In milk samples, it showed reliable glucose and H₂O₂ detection with recovery rates of 95–121% and relative standard deviations (RSD) of 0.31%–8.26%, demonstrating practical applicability. This Janus-structured GOx-Fe/Cu nanozyme improves GOx stability and sensing performance, and the hydrogel platform enables portable detection of glucose and hydrogen peroxide in food chemistry.