(612c) Good Dispersion and Intense Interaction Enhance Antibacterial Activity of Single-Walled Carbon Nanotubes

The toxicity and antibacterial activity of single walled carbon nanotubes (SWCNT) is related to their purity and aggregation. We previously developed a novel catalyst, cobalt-incorporated MCM-41 (Co-MCM-41) with controllable subnanometer scale metal clusters. It produces SWCNTs with a very narrow diameter distribution containing ca. 20 different (n,m) nanotubes. More recently, a centrifugation based purification protocol was developed to purify SWCNTs from Co-MCM-41 catalyst, by which SWCNT purity index based on absorption spectra of sodium cholate (SC) dispersed tubes is 0.268, approaching the previously estimated value (~0.325) for analytically pure SWCNTs. By tuning the centrifugation speeds, SWCNT samples containing different amounts of metallic resides (ranging between 19.28 at.% and 0.17 at.%) can be easily obtained. Furthermore, absorbed surfactant molecules such as SC can be eliminated by heating in air after removal of metallic residues. This allows us to re-dispersed ?clean? SWCNTs in biocompatible surfactants.

In this study, we compared the antibacterial activity of purified SWCNT samples dispersed in saline solution 0.9 wt% NaCl, 0.1 wt% Tween + 0.9 wt% NaCl, and 1 wt% SC on gram-negative bacterium (E. coli K12) and gram-positive bacterium (B.subtilis). Our results showed that good dispersion in non-toxic surfactants can greatly improve SWCNT antibacterial activity. Moreover, the antibacterial activity is correlated with interaction intensity between SWCNT and bacteria. Investigation of bacteria membrane stuffiness by atomic force microscope suggests that bacteria with more flexible membranes are more vulnerable to SWCNT piercing which results in membrane damage leading to higher cell death rate. We also show that the antimicrobial properties of SWCNTs are independent of cobalt residue concentration on SWCNT samples.

Reference:

Chen, Y.; Ciuparu, D.; Lim, S.; Yang, Y.; Haller, G. L.; Pfefferle, L., Synthesis of Uniform Diameter Single-Wall Carbon Nanotubes in Co-MCM-41: Effects of the Catalyst Prereduction and Nanotube Growth Temperatures. J. Catal. 2004, 225, (2), 453-465.

Chen, Y.; Ciuparu, D.; Lim, S.; Yang, Y.; Haller, G. L.; Pfefferle, L., Synthesis of Uniform Diameter Single Wall Carbon Nanotubes in Co-MCM-41: Effects of CO Pressure and Reaction Time. J. Catal. 2004, 226, (2), 351-362.

Wei, L.; Wang, B.; Wang, Q.; Li, L.-J.; Yang, Y.; Chen, Y., Effect of Centrifugation on the Purity of Single-Walled Carbon Nanotubes from MCM-41 Containing Cobalt. Journal of Physical Chemistry C 2008, 112, (45), 17567-17575.