Advanced Nanomaterials for Wastewater Remediation by Ravindra Kumar Gautam and Mahesh Chandra Chattopadhyaya

Author:Ravindra Kumar Gautam and Mahesh Chandra Chattopadhyaya
Language: eng
Format: epub, pdf
Publisher: CRC Press

8.4.3 CARBON NANOTUBES AS ANTIMICROBIAL MATERIALS

Advances in CNT research have shown that CNTs have antimicrobial mechanisms (Kang et al. 2007, 2008, 2009; Arias and Yang et al. 2009; Yang et al. 2010; Dong et al. 2012; Dizaj et al. 2015; Yah and Simate 2015), with Kang et al. (2007) being the first to show the antimicrobial activities of SWCNTs against Escherichia coli. The antimicrobial actions of CNTs and other nanomaterials include destruction of cell membranes, blockage of enzyme pathways, and alterations of microbial cell walls and nucleic material pathways (Yah and Simate 2015). Other antimicrobial mechanisms of nanomaterials include photocatalytic production of reactive oxygen species (ROSs) that can inactivate viruses and cleave DNA; disruption of the structural integrity of the bacterial cell envelope, resulting in leakage of intracellular components; and interruption of energy transduction (Mahendra et al. 2009). In particular, the antibacterial mechanism of CNTs is attributed to a physical interaction in which CNTs pierce cells (Mauter and Elimelech 2008; Li et al. 2008) or oxidative stress that compromises cell membrane integrity (Kang et al. 2007, 2008; Narayan et al. 2005).

Some studies have also shown that CNTs play a significant role in enhancing the activities of other antimicrobial agents (Yah and Simate 2015). For example, the combination of SWCNTs and hydrogen peroxide (H2O2) or NaOCl increases the sporicidal effect on the spores of organisms such as Bacillus species when compared with treatment with H2O2 or NaOCl alone at the same concentrations (Lilly et al. 2012). In such treatments, synergistic mechanisms of efficacy are established, due to the contribution of multiple antimicrobial effects. Further analysis shows that SWCNTs do not only play the role of antimicrobial effect, but also increase the permeability/susceptibility of the Bacillus species pathogen to H2O2 or NaOCl, thus significantly developing highly effective sporicidal effects (Lilly et al. 2012). Furthermore, findings by Gilbertson et al. (2014) found that oxygen functional groups, when functionalized on MWCNTs, can enhance several MWCNT properties such as redox, electrochemical, and antimicrobial activities. The redox activities include the ability to enhance the oxidation of glutathione and the reduction of surface carboxyl groups that promote the functional performance of MWCNTs’ antimicrobial activities for biomedical applications (Gilbertson et al. 2014).

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