Smartphone-integrated one-step colorimetric glucose detection at physiological pH enabled by a haloperoxidase mimic

Nanozymes (primarily peroxidase mimics) coupled with glucose oxidase (GOx) have emerged as an important approach for glucose sensing. However, the widespread application of this strategy is hampered by a critical pH mismatch, as most such nanozymes require an acidic environment for high activity, preventing one-step detection at physiological pH. Here, we report a cascade colorimetric sensing platform based on our previously reported haloperoxidase (HPO) mimic HH-Cu, which exhibits high HPO-like activity exclusively under neutral and alkaline conditions, enabling one-step glucose detection at physiological pH. In this system, GOx catalyzes the oxidation of glucose to generate H₂O₂, which is utilized by HH-Cu along with externally added Br^- to convert phenol red into bromophenol blue (λmax = 590 nm) through its HPO-like activity, resulting in a visible color change from orange to blue. Spectrophotometric analysis yielded a linear detection range of 1-600 μM and a detection limit of 0.99 μM for glucose, with recovery rates of 90.8%-106.6% and relative standard deviations (RSD) below 7% in urine samples. A smartphone-based analysis platform was also developed and showed performance comparable to the spectrophotometric method, with a linear range of 2.5-600 μM, a detection limit of 2.20 μM, and recovery rates of 105.5% in biological samples. Both platforms were also successfully applied to the sensitive detection of H₂O₂ at physiological pH. This work not only overcomes the key limitation of pH mismatch in conventional enzyme/nanozyme-based colorimetric glucose detection but also broadens the application horizon of HPO mimics in biosensing.