ATP-mediated intrinsic peroxidase-like activity of Fe3O4-based nanozyme: One step detection of blood glucose at physiological pH.

Fe3O4 nanoparticles (Fe3O4 NPs), demonstrating peroxidase-like activity has garnered attention in the detection of several biomolecules, therefore, emerged as an excellent nano-biosensing agent. The intrinsic peroxidase-like activity of Fe3O4 NPs at acidic pH is the fundamental action driving the oxidation of substrates like TMB, resulting in a colorimetric product formation used in the detection of biomolecules. Hence, the detection sensitivity essentially depends on the ability of oxidation by Fe3O4 NPs in presence of H2O2. However, the limited sensitivity and pH condition constraint have been identified as the major drawbacks in the detection of biomolecules at physiological pH. Herein, we report overwhelming of the fundamental limitation of acidic pH and tuning the peroxidase-like activity of Fe3O4 NPs at physiological pH by using ATP. In presence of ATP, Fe3O4 NPs exhibited enhanced peroxidase-like activity over a wide range of pH and temperatures. Mechanistically, it was found that the ability of ATP to participate in single electron transfer reaction, through complexation with Fe3O4 NPs, results in the generation of hydroxyl radicals which are responsible for enhanced peroxidase activity at physiological pH. We utilized this ATP-mediated enhanced peroxidase-like activity of Fe3O4 NPs for single step detection of glucose with a colorimetric detection limit of 50μM. Further, we extended this single step detection method to monitor glucose level in human blood serum and detected in a time span of <5min at pH 7.4.