Fabrication of Biomimetic Cascade Nanoreactor Based on Covalent Organic Framework Capsule for Biosensing

The cooperation of biocatalysis and chemocatalysis ina catalyticcascade reaction has received extensive attention in recent years,whereas its practical applications are still hampered due to the fragilityof the enzymes, poor compatibility between the carriers and enzymes,and limited catalytic efficiency. Herein, a biomimetic cascade nanoreactor(GOx@COFs@Os) was presented by integrating glucose oxidase (GOx) andOs nanozyme with covalent organic framework (COF) capsule using metal-organicframework (ZIF-90) as a template. The obtained GOx@COFs@Os capsuleprovided a capacious microenvironment to retain the conformationalfreedom of GOx for maintaining its activity, wherein the enzyme activityof GOx in COF capsules was equal to 92.9% of the free enzyme and was1.88-folds higher than that encapsulated in ZIF-90. Meanwhile, theCOF capsule could protect the GOx against incompatible environments(high temperature, acid, and organic solvents), resulting in improvedstability of the packaged enzymes. Moreover, the COF capsule withgreat pore structure significantly improved the affinity to substratesand facilitated efficient mass transfer, which achieved 2.19-foldsimprovement in catalytic efficiency than the free cascade system,displaying the great catalytic performance in the cascade reaction.More importantly, the biomimetic cascade capsule was successfullyemployed for glucose monitoring, glutathione sensing, and bisphenolS detection in the immunoassay as a proof-of-concept. Our strategyprovided a new avenue in the improvement of biocatalytic cascade performanceto encourage its wide applications in various fields.

Automated summary

The cooperation of biocatalysis and chemocatalysis in a catalytic cascade reaction has been widely studied. However, practical applications are hindered by enzyme fragility, poor compatibility between carriers and enzymes, and limited catalytic efficiency. In this study, a biomimetic cascade nanoreactor (GOx@COFs@Os) was developed, integrating glucose oxidase (GOx) and Os nanozyme with covalent organic framework (COF) capsules. The GOx@COFs@Os capsule provided a spacious microenvironment to retain GOx activity and protect it from incompatible environments. The COF capsule also improved substrate affinity and mass transfer efficiency, resulting in significantly improved catalytic efficiency compared to the free cascade system. Moreover, the biomimetic cascade capsule was successfully used for glucose monitoring, glutathione sensing, and bisphenol S detection. This strategy provides a new avenue for improving biocatalytic cascade performance and expanding its applications in various fields.