D. Henning, A. Pratsinis, G.A. Kelesidis, F. Krumeich, J.-C. Leroux, G.A. Sotiriou
Keywords: nanozyme, ceria, ratiometric, phosphorescence
Summary:Hydrogen peroxide (H2O2) is an abundant molecule associated with biological implications and reacts with natural enzymes, such as catalase. Thus, H2O2 quantification constitutes a powerful tool for detection of disease biomarkers linked to enzyme-based assays such as the plasmonic ELISA. However, the optical H2O2 biosensing without organic-dyes in biological media and at low, submicromolar, concentrations has yet to be achieved. The target of this work is to design biomimetic artificial enzymes based on antioxidant CeO2 nanoparticles that become luminescent upon their Eu3+ doping [1,2]. CeO2 nanoparticles have received a lot of attention recently due to their antioxidant enzyme-like (nanozyme) properties. Here, europium-doped cerium oxide (CeO2:Eu3+) nanoparticles with well-controlled size (d = 4 – 16 nm) are prepared by flame aerosol technology and characterized in regards to H2O2 sensor response in physiologically-relevant solutions. The developed biosensors are coupled to enzyme-based assays that consume or generate H2O2 aiming the detection of other important bioanalytes, such as alcohol and glucose, using alcohol oxidase enzymes, respectively. Upon the addition of a luminescent material with no H2O2 sensitivity, ratiometric sensors can be made for the facile and fast H2O2 detection in vitro. The biomimetic artificial enzyme developed here could serve as a starting point of sophisticated in vitro assays towards highly sensitive detection of disease biomarkers .  G. A. Sotiriou, M. Schneider & S. E. Pratsinis. J. Phys. Chem. C 115, 1084 (2011).  G. A. Sotiriou, D. Franco, D. Poulikakos & A. Ferrari. ACS Nano 6, 3888 (2012).  A. Pratsinis, G. A. Kelesidis, S. Zuercher, F. Krumeich, S. Bolisetty, R. Mezzenga, J.-C. Leroux & G. A. Sotiriou. ACS Nano 11, 12210 (2017).