Abstract
Cerium oxide nanoparticles (nano-CeO2) have been reported to cause damage and apoptosis in human primary hepatocytes. Here, we compared the toxicity of three types of nano-CeO2 with different nanocrystal morphologies (cube-, octahedron-, and rod-like crystals) in human hepatocellular carcinoma cells (HepG2). The cells were treated with the nano-CeO2 at various concentrations (6.25, 12.5, 25, 50, 100 μg/mL). The crystal structure, size and morphology of nano-CeO2 were investigated by X-ray diffractometry and transmission electron microscopy. The specific surface area was detected using the Brunauer, Emmet and Teller method. The cellular morphological and internal structure were observed by microscopy; apoptotic alterations were measured using flow cytometry; nuclear DNA, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and glutathione (GSH) in HepG2 cells were measured using high content screening technology. The scavenging ability of hydroxyl free radicals and the redox properties of the nano-CeO2 were measured by square-wave voltammetry and temperature-programmed-reduction methods. All three types of nano-CeO2 entered the HepG2 cells, localized in the lysosome and cytoplasm, altered cellular shape, and caused cytotoxicity. The nano-CeO2 with smaller specific surface areas induced more apoptosis, caused an increase in MMP, ROS and GSH, and lowered the cell’s ability to scavenge hydroxyl free radicals and antioxidants. In this work, our data demonstrated that compared with cube-like and octahedron-like nano-CeO2, the rod-like nano-CeO2 has lowest toxicity to HepG2 cells owing to its larger specific surface areas.
Highlights
Cerium oxide nanoparticles have a wide range of applications because of their desirable physical and chemical properties
The nanoparticles were synthesized hydrothermally, and their XRD patterns, shown in Figure 1, indicate that these particles were composed of cerium oxide in the typical fluorite cubic structure (JCPDS 34-0394)
The size and morphology of all nano-CeO2 are shown in Figure 2, and the results are in accordance with Table 1
Summary
Cerium oxide nanoparticles (nano-CeO2) have a wide range of applications because of their desirable physical and chemical properties. They have been used extensively in catalysis, polishing glass, solid oxide fuel cells and many other applications [1,2]. Nano-CeO2 has attracted considerable attention in the biomedical field. Other researchers have postulated that nanoCeO2 is an antioxidant because it eliminates reactive oxygen species [10,11,12,13] These two conflicting views are apparent on the safety of nano-CeO2. We aimed to compare the biological effects and toxicity of nano-CeO2 with different nanocrystal morphologies (cube-, octahedron-, and rod-like crystals) with an aim to find the safer morphology
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