A pilot toxicology study of single-walled carbon nanotubes in a small sample of mice

Single-walled carbon nanotubes are currently under evaluation in biomedical applications, including in vivo delivery(1-3) of drugs(4), proteins, peptides(5-7) and nucleic acids(8,9) ( for gene transfer(10) or gene silencing(11)), in vivo tumour imaging(12) and tumour targeting of single-walled carbon nanotubes as an anti-neoplastic treatment5. However, concerns about the potential toxicity of single-walled carbon nanotubes have been raised(13,14). Here we examine the acute and chronic toxicity of functionalized single-walled carbon nanotubes when injected into the bloodstream of mice. Survival, clinical and laboratory parameters reveal no evidence of toxicity over 4 months. Upon killing, careful necropsy and tissue histology show age-related changes only. Histology and Raman microscopic mapping demonstrate that functionalized single-walled carbon nanotubes persisted within liver and spleen macrophages for 4 months without apparent toxicity. Although this is a preliminary study with a small group of animals, our results encourage further confirmation studies with larger groups of animals.