Alkaline-Stable Peroxidase Mimics Based on Biological Metal–Organic Frameworks for Recyclable Scavenging of Hydrogen Peroxide and Detecting Glucose in Apple Fruits

Enzyme mimics constitute a promising class of biocatalysts with potential applications in bioanalysis, biomedicine, etc. due to their high catalytic activity and substrate specificity, but they often suffer from low operational stability and difficulties in recyclable utilization. Herein, we adopted an acid–base treatment to create an efficient enzyme mimic material by taking advantage of biological metal–organic frameworks (BioMOFs) constructed of the Cu2+ ion and a plant growth regulator. The prepared deprotonated dinuclear BioMOF exhibits excellent stability in alkaline environments and high peroxidase-mimicking activity. The enzyme mimic shows a quick reaction capability of H2O2 scavenging in the linear range of 0–0.2 μM mL–1 under neutral conditions and a sustained scavenging ability under strong alkaline conditions. Unlike general Cu-based peroxidase mimics, the BioMOF directly hydrolyzes H2O2 into O22– instead of the •OH radical and degrades to its synthetic precursor. The cyclic utilization, therefore, can be achieved by the interconversion between the BioMOF and its degraded product. Additionally, a hybrid nanomaterial (BioMOF-NPs) was developed by immobilizing the BioMOF and chitosan nanoparticles. The fabricated BioMOF-NPs display improved reliability and repeatability of the H2O2-scavenging effect due to the large specific surface area. Based on the BioMOF-NPs, selective glucose determination is achieved in the linear range of 5–25 μM with a detection limit of 1.93 μM. The method is successfully utilized for the recyclable detection of glucose in apple fruits. This study offers a new strategy for designing structure-interconvertible BioMOFs for applications of biological analysis.