Fluoride-assisted detection of glutathione by surface Ce3+/Ce4+ engineered nanoceria

Vaishwik Patel; Linta Jose; Gilles Philippot; Cyril Aymonier; Talgat Inerbaev; Luke R. McCourt; Michael G. Ruppert; Dongchen Qi; Wei Li; Jiangtao Qu; Rongkun Zheng; Julie Cairney; Jiabao Yi; Ajayan Vinu; Ajay S. Karakoti

doi:10.1039/D2TB01135B

Fluoride-assisted detection of glutathione by surface Ce³⁺/Ce⁴⁺ engineered nanoceria†

Vaishwik Patel,

^a Linta Jose,^a Gilles Philippot,^b Cyril Aymonier,

^b Talgat Inerbaev,^cd Luke R. McCourt,

^e Michael G. Ruppert,^e Dongchen Qi,^f Wei Li,^f Jiangtao Qu,

^g Rongkun Zheng,

^g Julie Cairney,^g Jiabao Yi,^a Ajayan Vinu

*^a and Ajay S. Karakoti

*^a

Author affiliations

* Corresponding authors

^a Global Innovative Center for Advanced Nanomaterials (GICAN), School of Engineering College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW, Australia
E-mail: ajayan.vinu@newcastle.edu.au, ajay.karakoti@newcastle.edu.au

^b Univ. Bordeaux, CNRS, Bordeaux INP, ICMCB, UMR 5026, F-33600 Pessac, France

^c L. N. Gumilyov Eurasian National University, Nur-Sultan 010008, Kazakhstan

^d National University of Science and Technology “MISIS”, Moscow 119049, Russia

^e School of Engineering, College of Engineering, Science and Environment, The University of Newcastle, Callaghan, Australia

^f Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4001, Australia

^g School of Physics, The University of Sydney, NSW, Australia

Abstract

Nanoceria has evolved as a promising nanomaterial due to its unique enzyme-like properties, including excellent oxidase mimetic activity, which significantly increases in the presence of fluoride ions. However, this significant increase in oxidase activity has never been utilised as a signal enhancer for the detection of biological analytes partly because of the lack of understanding of the mechanism involved in this process. In this study, we show that the surface oxidation state of cerium ions plays a very crucial role in different enzymatic activities, especially the oxidase mimetic activity by engineering nanoceria with three different surface Ce⁴⁺/Ce³⁺ compositions. Using DFT calculations combined with Bader charge analysis, it is demonstrated that stoichiometric ceria registers a higher oxidase mimetic activity than oxygen-deficient ceria with a low Ce⁴⁺/Ce³⁺ ratio due to a higher charge transfer from a substrate, 3,3′,5,5′ tetramethylbenzidine (TMB), to the ceria surface. We also show that the fluoride ions can significantly increase the charge transfer from the TMB surface to ceria irrespective of the surface Ce⁴⁺/Ce³⁺ ratio. Using this knowledge, we first compare the fluoride sensing properties of nanoceria with high Ce⁴⁺ and mixed Ce⁴⁺/Ce³⁺ oxidation states and further demonstrate that the linear detection range of fluoride ions can be extended to 1–10 ppm for nanoceria with mixed oxidation states. Then, we also demonstrate an assay for fluoride assisted detection of glutathione, an antioxidant with elevated levels during cancer, using nanoceria with a high surface Ce⁴⁺/Ce³⁺ ratio. The addition of fluoride ions in this assay allows the detection of glutathione in the linear range of 2.5–50 ppm with a limit of detection (LOD) of 3.8 ppm. These studies not only underpin the role of the surface Ce⁴⁺/Ce³⁺ ratio in tuning the fluoride assisted boost in the oxidase mimetic activity of nanoceria but also its strategic application in designing better colourimetric assays.

Journal of Materials Chemistry B

Fluoride-assisted detection of glutathione by surface Ce³⁺/Ce⁴⁺ engineered nanoceria†

Abstract

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Journal of Materials Chemistry B