Comparative toxicity and carcinogenicity pulmonary study of double-walled carbon nanotubes (DWCNT) with multi-walled carbon nanotubes-7 (MWCNTS -7) in a rat model

Abstract

Very little is known about the in vivo toxicity of inhaled double-walled carbon nanotubes (DWCNTs). In the present study, we compared the pulmonary toxicity of DWCNT to MWCNT-7, a well-known multi-walled carbon nanotube. Rats were divided into six groups: untreated, vehicle, low dose DWCNT, middle dose DWCNT, high dose DWCNT, and MWCNT-7. The test materials were administered by intra-tracheal intra-pulmonary spraying (TIPS) every other day for 15 days: the low dose, middle dose, and high-dose DWCNT groups were administered final total doses of 0.125, 0.25, and 0.50 mg/rat DWCNT and the MWCNT-7 group was administered 0.50 mg/rat MWCNT-7. The 1-year result showed DWCNT was internalized in granulation tissue. The granulation tissue was higher in the rats administered 0.5 mg DWCNT compared to the rats administered 0.50 mg MWCNT-7. Importantly, the number of macrophages was significantly increased in DWCNT treated rats compared to the control rats, and the number of macrophages in the 0.5 mg DWCNT treated rats was also significantly higher than in the 0.5 mg MWCNT-7 treated rats. However, the alveolar and mesothelial PCNA index were significantly higher in MWCNT-7 treated rats compared to the vehicle and DWCNT treated groups. Rats treated with DWCNT developed hyperplasia that was dose-dependent, but no adenomas or carcinomas were found in the lung or pleura of these rats. One rat administered MWCNT-7 developed mesothelioma. Conclusion: DWCNT was not shown to be carcinogenic to rats after 1 year, however, long-term studies are needed to predict the risk and safety of respirable DWCNT.