Ultrasensitive Hydrogen Peroxide Detection in Leafy Vegetables Using a Dual Chelate Metal Synergistic MOFzymes Biosensor

Although various MOFzymes have been used for H2O2 detection, their application in leafy vegetables remains limited. This was primarily due to the interference of complex matrices in leafy vegetables, which affected the detection process. Additionally, the free catalytic metal in MOFzymes could lead to color fading, resulting in unstable and time-consuming reactions. In this study, inspired by the multiactive sites and high selectivity of iron porphyrin-based MOFzymes, along with enhanced stability by chelated iron, we developed a highly sensitive and selective MOFzymes PCN222(Fe)-Gly(Fe)2. This enzyme used zirconium as the metal center, iron porphyrin chelated iron as the organic ligand, and ferrous glycine as a modifier. While the advantages of MOFzymes were retained, the synergistic impact and internal Fenton-like reaction improved the reaction rate, leading to a remarkable 310.2% increase in catalytic velocity. In field testing environments, the H2O2 content in Pakchoi seedling leaves could be determined within 100 s. In addition, the sensor demonstrated practical utility in predicting the shelf life and freshness of Pakchoi seedlings.