Comparative study on the catalytic activity of Fe-doped ZrO2 nanoparticles without significant toxicity through chemical treatment under various pH conditions

Hye-In Song,Jung A Hong,Kwang-Il Lim,Hangil Lee

doi:10.1038/s41598-019-47443-7

Abstract

Despite advances in the construction of catalysts based on metal oxide nanoparticles (MO NPs) for various industrial, biomedical, and daily-life applications, the biosafety concerns about these NPs still remain. Recently, the need to analyze and improve the safety of MO NPs along with attempts to enhance their catalytic performance has been strongly perceived. Here, we prepared multiple variants of Fe-doped zirconium oxide (Fe@ZrO2) NPs under different pH conditions; then, we assessed their toxicity and finally screened the variant that exhibited the best catalytic performance. To assess the NP toxicity, the prepared NPs were introduced into three types of human cells originally obtained from different body parts likely to be most affected by NPs (skin, lung, and kidney). Experimental results from conventional cellular toxicity assays including recently available live-cell imaging indicated that none of the variants exerted severe negative effects on the viability of the human cells and most NPs were intracellular localized outside of nucleus, by which severe genotoxicity is unexpected. In contrast, Fe@ZrO2 NPs synthesized under a basic condition (pH = 13.0), exhibited the highest catalytic activities for three different reactions; each was biochemical (L-cysteine oxidation) or photochemical one (4-chlorophenol degradation and OH radical formation with benzoic acid). This study demonstrates that catalytic Fe@ZrO2 NPs with enhanced activities and modest or insignificant toxicity can be effectively developed and further suggests a potential for the use of these particles in conventional chemical reactions as well as in recently emerging biomedical and daily-life nanotechnology applications.

Highlights

Introduction ofFe@ZrO2 NPs into cells.Base solutions containing Fe@ZrO2 NPs at the concentration of 100 mg/mL were prepared by mixing the synthesized Fe@ZrO2 NPs with UltraPureTM Distilled Water (Invitrogen)
Our study demonstrates that if appropriately prepared, Fe@ZrO2 NPs can facilitate the control of reactions relevant to biomedical applications without severe negative effects on human cells
Human cell uptake of NPs was observed using two cell-lines commonly chosen for toxicity assay, which had been originally isolated from the organs or tissues affected likely first and most by NPs: A431 cell line and Human embryonic kidney (HEK) 293T cell line[35,36]

Summary

Introduction

Base solutions containing Fe@ZrO2 NPs at the concentration of 100 mg/mL were prepared by mixing the synthesized Fe@ZrO2 NPs with UltraPureTM Distilled Water (Invitrogen). The base solutions were diluted further with distilled water to obtain solutions of lower NP-concentrations (2 and 10 mg/mL). Prior to introducing the NPs, the human cells were seeded and incubated in appropriate media (IMDM or RPMI 1640) for 24 h. Fe@ZrO2 NPs were introduced into the cells in wells of 12-well, 24-well, or 96-well plates to attain the predetermined final NP-concentrations of 20 and 100 μg/mL in the culture media. The cells were further incubated in the presence of NPs for three different periods (24, 48, and 72 h). For the 72 h incubation case, the culture medium was replaced with a fresh one at 48 h after NP-introduction, to keep the cells growing. Cells were incubated in the absence of NPs for comparison

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