Surface-engineered chitosan-coated MIL-53(Fe) nanozyme with synergistic effect on peroxidase/oxidase mimic as a highly sensitive biosensor for the colorimetric detection of hydrogen peroxide

The iron-based metal-organic framework (MOF) MIL-53(Fe) was successfully functionalized with chitosan through a simple and efficient post-synthetic strategy. This facile modification significantly enhances its catalytic properties, yielding a multifunctional nanocomposite that mimics both peroxidase and oxidase enzymatic activities. The chitosan-coated MIL-53(Fe), an inexpensive and biocompatible material, exhibits superior peroxidase-mimetic catalytic activity compared to its unmodified counterpart, enabling highly sensitive colorimetric biosensing. Upon interaction with hydrogen peroxide (H₂O₂), the nanocomposite facilitates the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), producing a deep blue solution with distinct UV–vis absorption peaks at 369 and 652 nm. This system demonstrates a detection limit of 0.3 μM. Furthermore, our optimized catalytic conditions (40 °C, pH 4.0, 10 min, catalyst concentration: 0.11 mg mL⁻¹) underscore the remarkable efficiency of our MOF-based peroxidase mimic. Notably, both peroxidase and oxidase activities are seamlessly executed under identical reaction conditions, simplifying multi-step enzymatic processes and eliminating the need for separate optimization protocols. This unique feature enhances overall efficiency while significantly reducing operational costs. The intrinsic rapid catalytic kinetics, reflected in the high V_max values of 147.77 × 10⁻⁸ Ms.⁻¹ for H₂O₂ and 53.11 × 10⁻⁸ Ms.⁻¹ for TMB, further reinforce the system's viability for real-time sensing applications. Our functionalized MIL-53(Fe) nanocomposite presents a groundbreaking advancement in MOF-based biomimetic catalysis, with high sensitivity, operational simplicity, and cost-effectiveness. Finally, due to the excellent catalytic activity of chitosan-coated MIL-53(Fe), it was successfully utilized to detect H₂O₂ in real samples, including tap water and well water.