Fast Colorimetric Detection of H2O2 and Glucose: A Way Based on Magnetic Nanoparticles Composed of Fe3(PO4)2·8H2O Isolated from Burkholderia cepacia CG-1

In this study, Fe3(PO4)2·8H2O magnetic nanoparticles (MNPs) were successfully extracted from the strain Burkholderia cepacia CG-1. We subsequently characterized their composition, structure, and morphology, revealing that these nanoparticles consisted of Fe3(PO4)2·8H2O with an average diameter of 66.87 ± 0.56 nm. Our measurements indicated magnetic parameters of 151 Oe for coercivity, 2 emu/g for saturation remanence, and 16 emu/g for saturation magnetization. Our findings confirmed that these magnetic nanoparticles exhibited intrinsic peroxidase-like activity, catalyzing the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2. Compared to horseradish peroxidase (HRP), the peroxidase mimic demonstrated greater stability under various physicochemical conditions. To investigate the mechanisms underlying the peroxidase-like catalysis of Fe3(PO4)2·8H2O, we employed fluorescence spectroscopy and electron spin resonance (ESR) analysis. The results revealed that the peroxidase-like activity of Fe3(PO4)2·8H2O stemmed from the generation of hydroxyl radicals (·OH). Furthermore, we established a platform for the colorimetric detection of H2O2 and glucose. Our method was capable of detecting H2O2 concentrations as low as 1.0 × 10−3 mmol/L. Impressively, this sensitive method was successfully applied to determine glucose levels in human serum.