Toxicity of nanomaterials

Abstract

Nanoscience has matured significantly during the last decade as it has transitioned from bench top science to applied technology. Presently, nanomaterials are used in a wide variety of commercial products such as electronic components, sports equipment, sun creams and biomedical applications. There are few studies of the long-term consequences of nanoparticles on human health, but governmental agencies, including the United States National Institute for Occupational Safety and Health and Japan's Ministry of Health, have recently raised the question of whether seemingly innocuous materials such as carbon-based nanotubes should be treated with the same caution afforded known carcinogens such as asbestos. Since nanomaterials are increasing a part of everyday consumer products, manufacturing processes, and medical products, it is imperative that both workers and end-users be protected from inhalation of potentially toxic NPs. It also suggests that NPs may need to be sequestered into products so that the NPs are not released into the atmosphere during the product's life or during recycling. Further, non-inhalation routes of NP absorption, including dermal and medical injectables, must be studied in order to understand possible toxic effects. Fewer studies to date have addressed whether the body can eventually eliminate nanomaterials to prevent particle build-up in tissues or organs. This critical review discusses the biophysicochemical properties of various nanomaterials with emphasis on currently available toxicology data and methodologies for evaluating nanoparticle toxicity (286 references).

Fig. 1

In vivo and in vitro studies for nanotoxicity research.

Fig. 2

Scheme showing the importance of the surface charge on the yield of cell uptake. Positively charged NPs illustrate significant cellular uptake, in comparison with negative and neutral ones, due to the attractive electrostatic interactions with the cell membrane. In addition, positively charged NPs are capable of acting as “proton sponges” that disrupt the lysosomes to enhance cytoplasmic delivery and induce cell death signaling cascades. The bottom left and right panels show TEM images of HeLa cells which have been exposed to negatively and positively charged SPIONs, respectively (unpublished work by M. Mahmoudi).

Fig. 3

The diverse forms of engineered nanomaterials: (a) C₆₀ dried onto filter paper is a black powder (inset: molecular structure of C₆₀); (b) fullerenes dissolved in a nonpolar solvent form a purple solution (top layer); and (c) with relatively mild chemical treatments, such as evaporation of the nonpolar phase, C₆₀ becomes water stable in the yellow aqueous phase. The material is present as colloidal aggregates that contain between 100–1000 fullerene molecules. (Reproduced with permission from ref. 286)