Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations

Abstract

Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating to toxicity are inevitable. The aim of this review is to compare synthetic (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of NPs and NSMs in the environment. The review presents an overview of the history and classifications of NMs and gives an overview of the various sources of NPs and NSMs, from natural to synthetic, and their toxic effects towards mammalian cells and tissue. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the associated risks are also discussed.

Keywords: nanomaterial classification; nanomaterial history; nanotoxicity; oxidative stress; reactive oxygen species; regulations.

Figure 1

Nanomaterials with different morphologies: (A) nonporous Pd NPs (0D) [–10], copyright Zhang et al.; licensee Springer, 2012, (B) Graphene nanosheets (2D) [11], copyright 2012, Springer Nature, (C) Ag nanorods (1D) [12], copyright 2011, American Chemical Society, (D) polyethylene oxide nanofibers (1D) [13], copyright 2010, American Chemical Society, (E) urchin-like ZnO nanowires (3D), reproduced from [14] with permission from The Royal Society of Chemistry, (F) WO₃ nanowire network (3D) [15], copyright 2005 Wiley-VCH.

Figure 2

FESEM of dust particle samples collected (a) during and (b) after the dust storm episodes on March 16, 2002 (scale bar 5 μm) [47], copyright 2005, the American Geophysical Union.

Figure 3

(a) SEM image of flaming smoke collected during a Madikwe Game Reserve fire in South Africa on August 20, 2000, showing aggregated carbon particles; (b) TEM image of flaming smoke collected in a Dambo fire in Zambia, on September 5, 2000, showing aggregated carbon particles [82], copyright 2003, the American Geophysical Union.

Figure 4

(A) Negatively stained rotavirus with complete (long arrow) and empty (short arrow) particles in swine feces [135], copyright Catroxo and Martins, 2015. (B) TEM image of a magnetotactic bacterium, reporduced with permission from [136], copyright 2014 Alphandéry.

Figure 5

Nanoparticles synthesized intracellularly in algae and fungi. (A) TEM micrograph of R. mucilaginosa yeast section showing (arrow) intracellular localization of Cu NPs [185], copyright 2015, Salvadori et al. (B) TEM photomicrograph of dead H. lixii fungal biomass section showing extracellular (lighter arrow) and intracellular (darker arrow) nickel oxide NPs [186], copyright 2015, Salvadori et al.

Figure 6

Photographs and the scanning electron microscope images of various bio-prototypes bearing superhydrophobic surfaces. (a) Photograph of a lotus leaf; (b) SEM image of the lotus leaf surface. The inset is a SEM image of a typical 5–9 µm micropapillae covering the surface with fine branch-like nanostructures [210], copyright 2002 Wiley-VCH. (c) Photograph of a red rose and (d) SEM image of a rose petal surface. The inset is a magnified SEM image of the microcapillary arrays [196,211], copyright 2008, American Chemical Society.

Figure 7

(A) Photograph of peacock feathers showing various colors and patterns. (B) Cross-sectional SEM images of the transverse (top) and longitudinal (bottom) sectionals of green barbule cortex [196], copyright 2012, Royal Society of Chemistry.

Figure 8

The macro- and microstructure of bone and its components with nanostructured materials employed in the regeneration of bone. (a) Macroscopic bone details with a dense cortical shell and cancellous bone with pores at both ends. (b) Repeating osteon units within cortical bone. (c) Collagen fibers (100–2000 nm) comprised of collagen fibrils [254], copyright 2015, Springer Nature.

Figure 9

Electron microscope images show how NPs can penetrate and relocate to various sites inside a phagocytic cell line. (A) Untreated phagocytic cell line (RAW 264.7). Cells were treated with (B) ultrafine particles (<100 nm) (C) TiO₂, (D) fullerol, (E) COOH–polystyrene nanospheres, and (F) NH₂polystyrene nanospheres. NP exposure was conducted by treating the cells with 10 μg/mL NPs (<100 nm) for 16 h. Labels: M = mitochondria, P = particles [288], copyright 1969, Americal Chemical Society.