ToxSci Advance Access published online on December 10, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn250
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Macrophage Responses to Silica Nanoparticles are Highly Conserved Across Particle Sizes
1 Environmental Biomarkers Program 2 Cell Biology and Biochemistry 3 Computational Biology and Bioinformatics 4 Materials Chemistry 5 Biomonitoring and Modeling Groups, Pacific Northwest National Laboratory, Richland, WA
* Correspondence: Brian D. Thrall, Cell Biology and Biochemistry Group, Pacific Northwest National Laboratory, Richland, Box 999, Mail Stop P7-56, WA, 99352. Tel. 509-376-3809; Fax. 509-376-6767; E-mail: brian.thrall{at}pnl.gov
Received September 29, 2008; revision received November 21, 2008; accepted November 28, 2008
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Abstract |
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Concerns about the potential adverse health effects of engineered nanoparticles stems in part from the possibility that some materials display unique chemical and physical properties at nanoscales which could exacerbate their biological activity. However, studies that have assessed the effect of particle size across a comprehensive set of biological responses have not been reported. Using a macrophage cell model, we demonstrate that the ability of unopsonized amorphous silica particles to stimulate inflammatory protein secretion and induce macrophage cytotoxicity scales closely with the total administered particle surface area across a wide range of particle diameters (7-500 nm). Whole genome microarray analysis of the early gene expression changes induced by 10 nm and 500 nm particles showed that the magnitude of change for the majority of genes affected correlated more tightly with particle surface area than either particle mass or number. Gene expression changes that were particle size-specific were also identified. However, the overall biological processes represented by all gene expression changes were nearly identical, irrespective of particle diameter. Direct comparison of the cell processes represented in the 10 nm and 500 nm particle gene sets using gene set enrichment analysis revealed that among 1009 total biological processes, none were statistically enriched in one particle size group over the other. The key mechanisms involved in silica nanoparticle-mediated gene regulation and cytotoxicity have yet to be established. However, our results suggest that on an equivalent nominal surface area basis, common biological modes of action are expected for nano- and supranano-sized silica particles.
Key Words: amorphous silica; nanoparticle; nanotoxicology; macrophage; inflammation.
¶ These authors contributed equally to this work