Toxic response of graphene nanoplatelets in vivo and in vitro

Abstract

With the development of nanotechnology, myriad types of novel materials have been discovered at the nanoscale, among which the most interesting material is graphene. However, the toxicity data available on graphene are extremely limited. In this study, we explored toxic response of commercially available graphene nanoplatelets (GNPs) in vivo and in vitro. The GNPs used in this study had a high surface area and feature considerably few defects. In mice, GNPs (2.5 and 5 mg/kg) remained in the lung until 28 days after a single instillation, and the secretion of inflammatory cytokines reached the maximal level at Day 14 and then decreased over time. In vitro study using BEAS-2B cells, a human bronchial epithelial cell line, GNPs located within autophagosome-like vacuoles 24 h after exposure. The GNPs (2.5, 5, 10, and 20 μg/mL) also dose-dependently reduced cell viability, which was accompanied by an increase in the portion of cells in the subG1 and S phases. Moreover, the GNPs down-regulated the generation of reactive oxygen species, suppressed ATP production, caused mitochondria damage, and elevated the levels of autophagy-related proteins. Based on these results, we suggest that GNPs provoked a subchronic inflammatory response in mice and that GNPs induced autophagy accompanying apoptosis via mitochondria damage in vitro.

The role of surface functionalization on the pulmonary inflammogenicity and translocation into mediastinal lymph nodes of graphene nanoplatelets in rats

“…However, lung inflammation was resolved 6 weeks after aspiration even though GNPs were persistent in the lung tissue (Schinwald et al 2014). Instillation of GNPs at 5 mg/kg in mice showed persistent localization in the alveoli, with peak expression of pro-inflammatory cytokines (e.g., granulocyte-macrophage colony-stimulating factor and monocyte chemoattractant protein-1) 14 days postinstillation (Park et al 2015). Inhalation of GNPs for five consecutive days at 10 mg/m 3 in rats showed no adverse effects, although GNPs were clearly localized in the cytoplasm of alveolar macrophages (Ma-Hock et al 2013).…”

The mechanisms of graphene-based materials-induced programmed cell death: a review of apoptosis, autophagy, and programmed necrosis

“…78 GNPs promoted autophagy by increasing the conversion from LC3B-I to LC3B-II and the level of p62 protein at 24 h after exposure in a dose-dependent manner in BEAS-2B cells. 79 Similarly, GQDs also significantly dose-dependently increased ROS generation and induced autophagy with an increase in the expression of LC3-II/I and Beclin-1 in macrophages or U251 human glioma cells. 26,47 Since autophagy may eliminate GBM particles or provide energy through cleaning the remnant organelle in cells, it may become a primary index to evaluate the toxicity of GBMs in occupational exposure or biomedical application.…”

“…GBMs have been shown to induce mitochondrial damage and provoke autophagy in a human bronchial epithelial cell line (BEAS-2B cells). 79 ROS and NO generation after GNPs treatment resulted in decreased numbers of mitochondria, ER, and Golgi apparatus, and mitochondrial fission-initiated mitochondrial autophagy. 96 GNPs dramatically increased the levels of p62 and Bcl-2 proteins to induce autophagy.…”

“…96 GNPs dramatically increased the levels of p62 and Bcl-2 proteins to induce autophagy. 79 The adaptor protein p62 can bind to ubiquitinated mitochondrial proteins and LC3 on autophagosomes, recruiting autophagic membranes for mitochondrial clearance. 97 Furthermore, Bcl-2 and Bcl-xL are antiapoptotic proteins that bind to Beclin-1, and the dissociation of the Bcl-2-Beclin-1 complex is essential for the initiation of autophagy.…”

The Role of Cell Autophagy in Toxicity Caused by Dental Nanomaterials

“…Furthermore, the levels of autophagy related genes, especially the DRAM1 gene, and the autophagosome formation related proteins, were clearly up regulated together with an increase of autophagosome like vacuoles. GNP has been proven to have a similar effect, caused mitochondria damage and elevated the levels of autophagy related proteins [28]. Functionalized Single Walled carbon Nanotubes (SWNT) restored normal autophagic activity by reversing abnormal activation of mTOR signaling and deficits in lysosomal proteolysis, thereby facilitating elimination of autophagic substrates [29].…”