(714a) Enzyme-Mimetic Luminescent Luminescent Nanoparticles As Hydrogen Peroxide Biosensors

Hydrogen peroxide (H₂O₂) is an abundant molecule associated with biological processes 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. Furthermore, we combine luminescent enzyme-mimetic CeO₂:Eu³⁺ nanoparticles with optically stable Y₂O₃:Tb³⁺ nanophosphors [1,2] that serve as concentration-independent reference value in the same nanoaggregates. Finally, the luminescence excitation is enhanced by the addition of Bi³⁺ within the same crystal matrix that improves its excitation in the near-UV wavelength region.

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 and glucose oxidase enzymes, respectively [3]. 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 sensing performance of the nanoparticles was further evaluated with hydrogen peroxide producing S. pneumoniae bacteria in biological media. Furthermore, the excitation spectrum engineering by the addition of Bi³⁺ ions renders these materials as suitable H₂O₂ biosensors with conventional fluorescent microscope filter sets utilizing the near-UV excitation. The biomimetic artificial enzyme developed here could serve as a starting point of sophisticated in vitro assays towards highly sensitive detection of disease biomarkers.

REFERENCES

[1] G.A. Sotiriou, M. Schneider & S.E. Pratsinis, “Color-Tunable Nanophosphors by Codoping Flame-Made Y2O3 with Tb and Eu”, J. Phys. Chem. C 115, 1084–1089 (2011).

[2] G.A. Sotiriou, D. Franco, D. Poulikakos, A. Ferrari, “Optically Stable Biocompatible Flame-Made SiO2-Coated Y2O3:Tb3+ Nanophosphors for Cell Imaging”, ACS Nano 6, 3888–3897 (2012).

[3] A. Pratsinis, G. A. Kelesidis, S. Zuercher, F. Krumeich, S. Bolisetty, R. Mezzenga, J-C. Leroux & G. A. Sotiriou. “Enzyme-Mimetic Antioxidant Luminescent Nanoparticles for Highly Sensitive Hydrogen Peroxide Biosensing” ACS Nano 11, 12210-12218 (2017).