The Puzzling Potential of Carbon Nanomaterials: General Properties, Application, and Toxicity

Abstract

Being a member of the nanofamily, carbon nanomaterials exhibit specific properties that mostly arise from their small size. They have proved to be very promising for application in the technical and biomedical field. A wide spectrum of use implies the inevitable presence of carbon nanomaterials in the environment, thus potentially endangering their whole nature. Although scientists worldwide have conducted research investigating the impact of these materials, it is evident that there are still significant gaps concerning the knowledge of their mechanisms, as well as the prolonged and chronic exposure and effects. This manuscript summarizes the most prominent representatives of carbon nanomaterial groups, giving a brief review of their general physico-chemical properties, the most common use, and toxicity profiles. Toxicity was presented through genotoxicity and the activation of the cell signaling pathways, both including in vitro and in vivo models, mechanisms, and the consequential outcomes. Moreover, the acute toxicity of fullerenol, as one of the most commonly investigated members, was briefly presented in the final part of this review. Thinking small can greatly help us improve our lives, but also obliges us to deeply and comprehensively investigate all the possible consequences that could arise from our pure-hearted scientific ambitions and work.

Keywords: carbon dots; carbon nanomaterials; carbon nanotubes; fullerene; graphene; in vitro and in vivo research; nanodiamonds; toxicity.

Figure 1

Pros and cons for the carbon nanomaterials (CNMs) use, original figure.

Figure 2

The main physicochemical properties of different nanostructures fullerene (C₆₀); fullerenol (C₆₀(OH)₂₄); carbon dots (CDs); nanodiamonds (NDs); single-walled carbon nanotube (SWCNT); multi-walled carbon nanotube (MWCNT); graphene oxide (GO).

Figure 3

(a) TEM/HR-TEM images of different carbon nanomaterials: C₆₀ nanoparticles (scale bar = 100 nm), original figure; (b) nanodiamonds (scale bar = 5 nm), adapted from [26], (c) carbon nanotubes (CNTs) (scale bar = 2 μm), original figure; (d) graphene oxide (scale bar = 500 nm), adapted from [27].

Figure 4

General scheme of cell signaling cascade, original figure.

Figure 5

Cell signaling events induced by CNTs, original figure. In different cell types, CNTs induce reactive oxygen species (ROS)-dependent activation of certain cell signaling pathways (NF-κB, MAPK, AP-1), and subsequently, secretion of proinflammatory cytokines (in macrophages and epithelial cells) or profibrogenic and angiogenic factors (in macrophages and lung fibroblasts). Proinflammatory cytokines (IL-1β, IL-6, IL-10, TNF-α, MCP-1) are responsible for inflammation, profibrogenic factors (TGF-β1, PDGF) cause fibroproliferation and differentiation of fibroblast to myofibroblast, while growth factor (VEGF), as well as proinflammatory cytokines, initiates angiogenesis. (NF-nuclear factor, MAPK-mitogen-activated protein kinase, AP-activator protein, IL-interleukine, TNF-tumour necrosis factor, MCP-monocyte chemoattractant protein, TGF-transforming growth factor, PDGF-platelet-derived growth factor, VEGF-vascular endothelial growth factor).

Figure 6

Twenty-four-hour median lethal dose (LD₅₀) of fullerenol nanoparticles (FNPs) for an intraperitoneal (i.p.) route of administration; (a) calculated LD₅₀ value after the application of four increasing doses of FNPs [178]; (b) calculated LD₅₀ value after the application of three increasing doses of FNPs [179], original figure.