Preparation of graphene nano-sheet bonded PDA/MOF microcapsules with immobilized glucose oxidase as a mimetic multi-enzyme system for electrochemical sensing of glucose

A novel amperometric biosensor for glucose detection was fabricated based on a mimetic multi-enzyme system by combing mimetic enzymes (metal-organic frameworks, MOFs) and glucose oxidase (GOx). The microcapsule constructed with polydopamine (PDA) and ZIF-8 using CaCO₃ templates could be utilized not only to provide the biocompatible and non-toxic microenvironment to immobilize GOx, but also as an efficient mimetic enzyme because of the peroxidase-like properties of ZIF-8. The graphene nano-sheets (rGO) were bonded to the PDA/ZIF-8 microcapsules to accelerate the electron transfer between the microcapsule and the electrode, and the resulted PDA/ZIF-8@rGO showed excellent electro-catalytic activity towards H₂O₂. The mimetic multi-enzyme system was fabricated when GOx was immobilized in the as-prepared microcapsule, and the developed GOx/PDA/ZIF-8@rGO/GCE biosensor exhibited extraordinary electro-detection performance for glucose with two wide linear ranges from 1 μM to 1.2 mM and 1.2 mM to 3.6 mM, and the limit of detection was 0.333 μM (S/N = 3). Moreover, the good selectivity for glucose and satisfactory detection results in real samples of the prepared biosensor were also demonstrated.