Mechanistic understanding of toxicity from nanocatalysts

Abstract

Nanoparticle-based catalysts, or nanocatalysts, have been applied in various industrial sectors, including refineries, petrochemical plants, the pharmaceutical industry, the chemical industry, food processing, and environmental remediation. As a result, there is an increasing risk of human exposure to nanocatalysts. This review evaluates the toxicity of popular nanocatalysts applied in industrial processes in cell and animal models. The molecular mechanisms associated with such nanotoxicity are emphasized to reveal common toxicity-inducing pathways from various nanocatalysts and the uniqueness of each specific nanocatalyst.

Figure 1

The expected benefits of nanocatalysis. Reprinted from [2] with permission from Wiley-VCH Verlag GmbH & Co. KGaA, Copyright 2013.

Figure 2

Surface chemistry modification of MWCNT (multi-walled carbon nanotube) 2 significantly alleviated NF-κB activation and reduced the immunotoxicity caused by unmodified MWCNT 1. Adapted from [71] with permission from the American Chemical Society, Copyright 2011.

Figure 3

TNP (titanium dioxide nanoparticle) exposure-induced photodependent delays in development, decreased growth, and tissue malformation and possible mechanisms. Fish were exposed to illumination in all cases with (A) water as a control; (B) Degussa TNPs (1 ng/mL); or (C) Sun Innovations TNPs (1 ng/mL). Representative effects of the TNPs were indicated. The red arrows show the normal bi-lobed swim bladder in the control and the single-lobed swim bladder in the treated fish. The small blue points indicate the row of developing melanophores making an unbroken line in the normal fish, and underdeveloped in the treated fish. Fin rays in the normal fish are indicated by a white arrow, and the angle of the notochord as it intersects the caudal fin is indicated by a black line and blue arrow. The black arrow indicates the snout shortening and related craniofacial malformations caused by treatment. Possible mechanisms of illumination-induced ROS (reactive oxygen species) generation were performed in (D). Adapted from [110,111] with permissions from the American Chemical Society, Copyright 2009, 2013.

Figure 4

The surface hydrophobicity of GNPs (gold nanoparticles) dictates immune responses in splenocytes. Reprinted from [130] with permission from the American Chemical Society, Copyright 2012.

Figure 5

A proposed pathway for Ag NP-induced ROS generation, intracellular glutathione (GSH) depletion, damage to cellular components, and apoptosis. Reprinted from [174] with permission from Elsevier, Copyright 2011.

Figure 6

Schematic representation of the different intracellular uptake pathways of SPIONPs (superparamagnetic iron oxide nanoparticles) (8-OH-dG, 8-hydroxydeoxyguanosine; MDA, malondialdehyde; HNE, 4-hydroxy-2-nonenal). Reprinted from [195] with permission from Singh et al. [195], Copyright 2010.