Hydrogen Peroxide Displacing DNA from Nanoceria: Mechanism and Detection of Glucose in Serum

Hydrogen peroxide (H₂O₂) is a key molecule in biology. As a byproduct of many enzymatic reactions, H₂O₂ is also a popular biosensor target. Recently, interfacing H₂O₂ with inorganic nanoparticles has produced a number of nanozymes showing peroxidase or catalase activities. CeO₂ nanoparticle (nanoceria) is a classical nanozyme. Herein, a fluorescently labeled DNA is used as a probe, and H₂O₂ can readily displace adsorbed DNA from nanoceria, resulting in over 20-fold fluorescence enhancement. The displacement mechanism instead of oxidative DNA cleavage is confirmed by denaturing gel electrophoresis and surface group pK_a measurement. This system can sensitively detect H₂O₂ down to 130 nM (4.4 parts-per-billion). When coupled with glucose oxidase, glucose is detected down to 8.9 μM in buffer. Detection in serum is also achieved with results comparable with that from a commercial glucose meter. With an understanding of the ligand role of H₂O₂, new applications in rational materials design, sensor development, and drug delivery can be further exploited.