Research

Particle length-dependent titanium dioxide nanomaterials toxicity and bioactivity

Raymond F Hamilton Jr¹ , Nianqiang Wu² , Dale Porter³ , Mary Buford¹ , Michael Wolfarth³ and Andrij Holian¹

¹  Center for Environmental Health Sciences, University of Montana, Missoula MT, USA

²  Mechanical and Aerospace Engineering, WV Nano Initiative, West Virginia University, Morgantown, WV 26506-6106, USA

³  Health Effects Laboratory Division, NIOSH, Morgantown, VW, USA

author email corresponding author email

Particle and Fibre Toxicology 2009, 6:35doi:10.1186/1743-8977-6-35

Published:	31 December 2009

Abstract

Background

Titanium dioxide (TiO₂) nanomaterials have considerable beneficial uses as photocatalysts and solar cells. It has been established for many years that pigment-grade TiO₂ (200 nm sphere) is relatively inert when internalized into a biological model system (in vivo or in vitro). For this reason, TiO₂ nanomaterials are considered an attractive alternative in applications where biological exposures will occur. Unfortunately, metal oxides on the nanoscale (one dimension < 100 nm) may or may not exhibit the same toxic potential as the original material. A further complicating issue is the effect of modifying or engineering of the nanomaterial to be structurally and geometrically different from the original material.

Results

TiO₂ nanospheres, short (< 5 μm) and long (> 15 μm) nanobelts were synthesized, characterized and tested for biological activity using primary murine alveolar macrophages and in vivo in mice. This study demonstrates that alteration of anatase TiO₂ nanomaterial into a fibre structure of greater than 15 μm creates a highly toxic particle and initiates an inflammatory response by alveolar macrophages. These fibre-shaped nanomaterials induced inflammasome activation and release of inflammatory cytokines through a cathepsin B-mediated mechanism. Consequently, long TiO₂ nanobelts interact with lung macrophages in a manner very similar to asbestos or silica.

Conclusions

These observations suggest that any modification of a nanomaterial, resulting in a wire, fibre, belt or tube, be tested for pathogenic potential. As this study demonstrates, toxicity and pathogenic potential change dramatically as the shape of the material is altered into one that a phagocytic cell has difficulty processing, resulting in lysosomal disruption.