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Carbon Nanotube Bacterial Cytotoxicity: Does the Type of Carbon Nanotubes Matter?

Seoktae Kang1, Moshe Herzberg2, Debora F. Rodrigues1, and Menachem Elimelech1. (1) Department of Chemical Engineering, Environmental Engineering Program, Yale University, Mason Laboratory 204, 9 Hillhouse Ave., New Haven, CT 06520, (2) Department of Desalination and Water Treatment, Ben Gurion University of the Negev, Zuckerberg Institute for Water Research, Sede-Boqer Campus, Midreshet Ben Gurion, 84990, Israel

We investigate the bacterial toxicity of well-characterized carbon nanotubes (CNTs) by several independent techniques. Results demonstrate that single-walled carbon nanotubes (SWNTs) are much more toxic to bacteria (E. coli) than multi-walled carbon nanotubes (MWNTs). The likely main CNT-cytotoxicity mechanism is cell membrane damage by direct contact with CNTs. Gene expression data shows that in the presence of both MWNTs and SWNTs, E. coli express high levels of stress-related gene products, with the quantity and magnitude of expression being much higher in the presence of SWNTs. The enhanced bacterial toxicity of SWNTs may be attributed to: (1) a smaller nanotube diameter that facilitates partitioning and partial penetration of nanotubes into the cell wall, (2) a larger surface area for contact and interaction with the cell surface, and/or (3) unique chemical and electronic properties conveying greater chemical reactivity.