Picomolar Detection of Hydrogen Peroxide using Enzyme-free Inorganic Nanoparticle-based Sensor

A philosophical shift has occurred in the field of biomedical sciences from treatment of late-stage disease symptoms to early detection and prevention. Ceria nanoparticles (CNPs) have been demonstrated to neutralize free radical chemical species associated with many life-threatening disease states such as cancers and neurodegenerative diseases by undergoing redox changes (Ce3+ <-> Ce4+). Herein, we investigate the electrochemical response of multi-valent CNPs in presence of hydrogen peroxide and demonstrate an enzyme-free CNP-based biosensor capable of ultra-low (limit of quantitation: 0.1 pM) detection. Several preparations of CNPs with varying Ce3+:Ce4+ are produced and are analyzed by electrochemical methods. We find that an increasing magnitude of response in cyclic voltammetry and chronoamperometry correlates with increasing Ce4+ relative to Ce3+ and utilize this finding in the design of the sensor platform. The sensor retains sensitivity across a range of pH's and temperatures, wherein enzyme-based sensors will not function, and in blood serum: reflecting selectivity and robustness as a potential implantable biomedical device.