Inactivation of Bacterial Pathogens by Carbon Nanotubes in Suspensions

Abstract

In the study, we explored the antimicrobial activities of single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs) with different surface groups to bacterial pathogens, including Gram-negative vs Gram-positive species and rod-shaped vs round-shaped species. We report here for the first time that SWNTs' antimicrobial activity is buffer and concentration dependent, and the charge effect of functional groups on the surface of carbon nanotubes (CNTs) is not a critical factor. SWNTs with surface groups of -OH and -COOH exhibited extremely strong antimicrobial activity to both Gram-positive and Gram-negative bacterial cells in DI water and 0.9% NaCl solution regardless of cell shape, but they did not exhibit antimicrobial activity in PBS buffer and brain heart infusion broth. The antimicrobial activities of these two SWNTs increased with their concentration and treatment time. In DI water or 0.9% NaCl solution, SWNTs-OH and SWNTs-COOH started to show their antimicrobial activity at approximately 50 microg/mL; when their concentration increased to 200-250 microg/mL, they could inactivate 10(7) cfu/mL Salmonella cells in 15 min. The approximately 7 log reduction in viable cell count achieved by this CNTs-based method exceeded those of many reported antimicrobial methods. SWNTs-NH2 only exhibited antimicrobial activity at higher concentrations. MWNTs with surface groups of -OH, -COOH, and -NH2 did not show any significant antimicrobial activity to all tested bacterial cells in any of the tested buffers at concentrations up to 500-875 microg/mL. Formation of cell-CNTs aggregates were studied using fluorescence and electron scanning microscopes. The possible mechanism of SWNTs' antimicrobial activities was also discussed.

Graphene oxide/multi-walled carbon nanotubes as nanofeatured scaffolds for the assisted deposition of nanohydroxyapatite: characterization and biological evaluation

“…These results are in accordance with those of Arias and Yang, and Liu et al, although those experiments were conducted differently and substrates were formulated differently. 59,60 The same observation was reported by Dong et al where single-walled carbon nanotube (SWCNT) tests indicated that the nanotube concentration is the deciding factor for an antibacterial effect. 61 Our results showed that increasing the MWCNT concentration (from 10 to 100 µg mL -1 ) led to increases in the bactericidal effect against E. coli and S. aureus, and these results are very similar to those observed in a study by Liu et al, which reported that the death rate of E. coli increased with an increase in SWCNT concentration from 5 to 80 µg mL…”

Heteroaggregation of nanoparticles with biocolloids and geocolloids

“…Heteroaggregation between NPs and cells occur rapidly [110,120,126], and heteroaggregates may continue to grow over time if conditions are favorable [126]. Heteroaggregation may be due to weak physical interactions via DLVO and non-DLVO forces [114] as disaggregation (desorption) has been reported in aqueous conditions that may not affect strong chemical bonds.…”

Oxidative stress-mediated antibacterial activity of graphene oxide and reduced graphene oxide in Pseudomonas aeruginosa

“…15,26 Specifically, single-walled CNTs (SWNTs) show the strongest antimicrobial activity. [31][32][33][34] Liao et al 35 reported a concentration-dependent toxicity of GO and graphene in human erythrocytes and skin fibroblasts. Involvement of the reactive oxygen species (ROS) generated by graphene was proposed as one of the main mechanisms for the cytotoxicity of graphene at high concentrations (100 mg/mL) in neural pheochromocytoma-derived PC12, 36 and the size of GO sheets has an effect on the toxicity of GO of high concentration, ie, larger sheets have better biocompatibility in A549 cells.…”