In this study, we investigated the sporicidal effects of single-walled carbon nanotubes (SWCNTs) and SWCNTs combined with oxidizing antimicrobial chemicals, H₂O₂ and NaOCl, on B. anthracis spores. The results indicated that treatment with SWCNTs alone exhibited little sporicidal effect on B. anthracis spores, while treatment with H₂O₂ or NaOCl alone showed moderate sporicidal effect. The combination treatment with SWCNTs (100 μg/mL) and H₂O₂ (1.5%) or NaOCl (0.25%) exhibited much stronger sporicidal effect on the spores, compared to treatment with H₂O₂ or NaOCl alone at the same concentrations, doubling the log reduction of viable spore number (∼3.3 log vs ∼1.6 log). Such enhanced sporicidal efficiency was due to the synergistic effect contributed by the two individual antimicrobial mechanisms of SWCNTs and the oxidizing antimicrobial chemicals. The ordered sequential treatment with SWCNTs and H₂O₂ or NaOCl revealed that SWCNTs played the key role in making the spores more permeable/susceptible to chemicals. This study demonstrated the potential of combination treatment with SWCNTs and oxidizing antimicrobial agents in developing highly effective sporicidal agents/methods.

In this study, the effect of single-walled carbon nanotubes (SWCNTs) on B. anthracis cell growth, spore formation, and spore germination was studied. We found that SWCNTs at a concentration of 100 microg/ml exhibited obvious antimicrobial activity on 10(6) cfu/ml B. anthracis cells. At 300 microg/ml, 1 h of SWCNTs treatment could inactivate B. anthracis cells by approximately 2 log viable cell reduction. The SWCNT treatment did not induce spore formation. We also found that SWCNTs were not effective in the inactivation of B. anthracis spores at concentrations from 50 microg/ml up to 300 microg/ml. Fluorescence microscopy and scanning electron microscopy were used to examine the interactions between SWCNTs and B. anthracis cells/spores. Analysis of these microscopic images suggested that the direct contact between SWCNTs and B. anthracis cells lead to cell membrane damage and the inactivation of cells, whereas the lack of tight direct contact between SWCNTs and spores was the reason accounting for its ineffectiveness in inactivating spores.

Inactivation of pathogens from environment and inhibition of bio¯lm formation on various surfaces are important for biosafety, biosecurity and public health. Carbon nanotubes (CNTs) possess antimicrobial e®ects in addition to their unique optical, electrical, mechanical and thermal properties. This review summarizes the antimicrobial e®ects of single walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) in suspensions and on CNT contained surfaces. To increase antimicrobial e®ects, CNT composites containing other antimicrobial reagents are introduced. Also described are the possible antimicrobial mechanisms of CNTs.