Sharper and Faster “Nano Darts” Kill More Bacteria: A Study of Antibacterial Activity of Individually Dispersed Pristine Single-Walled Carbon Nanotube

Abstract

To further our understanding on the antibacterial activity of single-walled carbon nanotubes (SWCNTs), high purity SWCNTs with average diameter of 0.83 nm and (7,5) chirality as dominate (n,m) structure were dispersed in a biocompatible surfactant solution. Ultraviolet-visible-near-infrared radiation absorption spectroscopy was employed to monitor the aggregation of SWCNTs. The results demonstrated that individually dispersed SWCNTs were more toxic than SWCNT aggregates toward bacteria (gram-negative Escherichia coli, Pseudomonas aeruginosa, and gram-positive Staphylococcus aureus, Bacillus subtilis). Individually dispersed SWCNTs can be visualized as numerous moving "nano darts" in the solution, constantly attacking the bacteria; thereby, degrading the bacterial cell integrity and causing the cell death. Controlled experimental results suggested that inhibiting cell growth and oxidative stress were not the major causes responsible for the death of cells. Furthermore, the detrimental effects of Co metal residues (up to 1 mug/mL) on SWCNT samples can be ruled out. Atomic force microscope study conducted in suspension proved that the death rates of bacteria were strongly correlated with their mechanical properties; soft cells were more vulnerable to SWCNT piercing. The antibacterial activity of SWCNTs can be remarkably improved by enhancing the SWCNT physical puncture on bacteria in the following ways: (1) dispersing SWCNTs individually to sharpen the nano darts; (2) increasing SWCNT concentration to raise the population density of nano darts; and (3) elevating the shaking speed of incubation to speed up the nano darts. This study elucidated several factors controlling the antibacterial activity of pristine SWCNTs and it provided an insight in developing strategies that can maximize the SWCNT application potentials while minimizing the health and environment risks.

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…”

Innovative biofilm inhibition and anti-microbial behavior of molybdenum sulfide nanostructures generated by microwave-assisted solvothermal route

“…After thorough washing with CB, samples were dehydrated in a series of ethanol solutions (10-100 %). The samples were dried, mounted on aluminum stubs with conductive carbon cement, and finally coated with a gold film for observation under FESEM (Hitachi 4800 SEM at 1.5 kV) (Liu et al 2009). For CLSM, after initial through washing, the biofilm was covered with 50 lL of 100 lg/ml of dye, concanavalin A, alexaflour 488, and incubated for 30 min at 4°C.…”

Fe3+-saturated montmorillonite effectively deactivates bacteria in wastewater

“…With mixture of the SYTO 9® and propidium iodide (PI), bacteria with intact cell membranes stain fluorescent green (considered to be viable), and bacteria with compromised membranes stain fluorescent red (considered to be nonviable). Similar fluorescence dye methods have been applied in other studies monitoring the antibacterial properties of nanoparticles (Liu et al, 2009;Perreault et al, 2015;Raghupathi et al, 2011).…”

“…In general, bacterial deactivation can be the result of: 1) direct mechanical breakage of outer cell membranes by sharp edged nanoparticles (Akhavan and Ghaderi, 2010;Liu et al, 2009;Situ and Samia, 2014); 2) chemical oxidative stress mediated cell injury that is induced by in situ production of reactive oxygen species (Krishnamoorthy et al, 2012;Su et al, 2009); and 3) dehydration of cell membrane (Beney et al, 2004). It is highly likely that the latter two bacterial deactivation mechanisms are at play when wastewater is exposed to Fe 3+ -saturated montmorillonite.…”