Abstract
Several in vivo studies suggest that nanoparticles (smaller than 100 nm) have the ability to reach the brain tissue. Moreover, some nanoparticles can penetrate into the brains of murine fetuses through the placenta by intravenous administration to pregnant mice. However, it is not clear whether the penetrated nanoparticles affect neurogenesis or brain function. To evaluate its effects on neural stem cells, we assayed a human neural stem cell (hNSCs) line exposed in vitro to three types of silica particles (30 nm, 70 nm, and <44 μm) and two types of titanium oxide particles (80 nm and < 44 μm). Our results show that hNSCs aggregated and exhibited abnormal morphology when exposed to the particles at concentrations ≥ 0.1 mg/mL for 7 days. Moreover, all the particles affected the gene expression of Nestin (stem cell marker) and neurofilament heavy polypeptide (NF-H, neuron marker) at 0.1 mg/mL. In contrast, only 30-nm silica particles at 1.0 mg/mL significantly reduced mitochondrial activity. Notably, 30-nm silica particles exhibited acute membrane permeability at concentrations ≥62.5 μg/mL in 24 h. Although these concentrations are higher than the expected concentrations of nanoparticles in the brain from in vivo experiments in a short period, these thresholds may indicate the potential toxicity of accumulated particles for long-term usage or continuous exposure.
Highlights
Recent technical advances have enabled mass production of various nanomaterials, such as silica, titanium oxide, and carbon nanotubes
We studied the properties of SP30, SP70, SPM, TP80, and TPM particles
Because only the mitochondrial activities of human NSCs (hNSCs) exposed to FL-SP30 were decreased significantly (p < 0.05), we focused on the toxicological effects of 30-nm silica particles
Summary
Recent technical advances have enabled mass production of various nanomaterials, such as silica, titanium oxide, and carbon nanotubes. There is a concern that some characteristics of nanomaterials, such as their tube- or fiber-like structures with rigid properties or certain sizes, might cause toxicity similar to that of asbestos [5,6,7]. Both in vitro and in vivo studies of nanoparticles toxicity are currently in progress [8,9,10,11,12,13]. Generation by cells that uptake titanium oxide particles [14,15] or silicon/silica particles [16,17]; and (2) the release of metallic material from Cd/Se quantum dots (QDs) after UV exposure [16] or silver particles [18]; and (3) structure-related toxicity caused by multi-walled carbon nanotubes [19].
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