A versatile biomimetic multienzyme cascade nanoplatform based on boronic acid-modified metal-organic framework for colorimetric biosensing.

The combination of bio- and chemo-catalysts for sequential cascades has received considerable attention in analytical fields because of the regulable catalytic efficiency and selectivity under various physiological conditions. In this paper, a versatile multienzyme cascade nanoplatform with excellent activity for biosensing is demonstrated by combining metal-organic framework (MOF)-based nanozyme with natural enzymes. A boronic acid-modified MOF, MIL-100(Fe)-BA, was obtained via a microwave-assisted metal-ligand-fragment co-assembly strategy. On the one hand, MIL-100(Fe)-BA could serve as a nanozyme with dual oxidase/peroxidase bioactivity to detect glutathione and ascorbic acid with a detection limit of 0.12 μM and 0.09 μM, respectively. On the other hand, the hierarchically porous MIL-100(Fe)-BA possesses adequate recognition sites for immobilizing enzymes with acceptable protein leakage, enabling it to act like a scaffold for the fixation of a single enzyme (sarcosine oxidase) or bi-enzymes (acetylcholinesterase/choline oxidase) and guide a multienzyme cascade reaction system with high efficiency. The cascade nanoplatform has merits of both artificial nanozymes and natural enzymes, providing satisfactory sarcosine/acetylcholine sensing ability with detection limits of 0.26 μM and 1.18 μM. The developed catalytic system not only expands the application of nanozymes in tandem enzymatic bio-catalysis, but provides a facile and efficient multienzyme cascade nanoplatform for biosensing and other applications.