Glucose oxidase-integrated boron-doped MIL-100(Fe) nanozyme with enhanced peroxidase-like activity for portable glucose biosensing

In this work, a boronic acid decorated mesoporous iron-based metal-organic framework (MIL-100(Fe)-B) nanozyme as an efficient immobilization matrix for glucose oxidase (GOx) was designed and prepared through a facile microwave-assisted metal-ligand-fragment co-assembly strategy. Compared with the unboric acid-modified MIL-100(Fe), boron-doped MIL-100(Fe) exhibited enhanced peroxidase-like activity, which was mainly due to the introduced B causing MIL-100(Fe) defects, accelerating mass transfer, facilitating more active sites for H2O2 decomposition. Besides, the MIL-100(Fe)-B nanozyme possessed sufficient recognition sites for immobilizing glucose oxidase with little enzyme leakage to form a cascade nanozyme with both peroxidase-like and cascade catalytic activities. A colormetric biosensor based on the integrated nanozyme reactor (GOx@MIL-100(Fe)-B) was developed for glucose detection. The proposed cascade biosensor had a linear range of 5-150 μM and a limit of detection (LOD) of 0.97 μM (3.3 δ/S). Interestingly, a portable microfluidic paper-based analytic device (μPAD) biosensor based on the cascade nanoplatform was further fabricated for visualized detection of glucose combined with a ColorPicker App on smartphone. It indicated that the integrated nanozyme GOx@MIL-100(Fe)-B was a promising candidate for glucose detection and provided a potentially analytical avenue for biosensing and other applications.