| dc.description.abstract | In recent years, nanotechnology has been widely applied in various fields, leading to further innovations in the corresponding sector. As such, nanotechnology is considered one of the most important emerging technologies in the 21st century. However, the large-scale production and a wide range use of engineered nanomaterials will eventually increase the chance of these novel materials entering the environment and become a new generation of pollutants. In our previous study, it was observed that while nitric acid reflux of carbon nanotubes (CNTs) effectively increased the dispersion of CNTs in water, toxicity of suspended CNTs on planktonic bacteria was significantly reduced. This might be due to surface electrostatic repulsion between CNTs and bacterial cells. However, the exact cause behind this observation remains to confirm. Therefore, to determine whether the surface charge is a critical factor controlling the antibacterial effect of CNTs, multi-walled carbon nanotubes (MWCNTs) and E. coli were used as model CNTs and microorganism respectively in this study. Surface functionalization of MWCNTs resulted in carboxyl- (i.e., MWCNT-COOH) and amino-containing MWCNTs (i.e., MWCNT-ETA) that had surface potentials of -27.70 mV and -3.00 mV, respectively. FTIR and TGA analyses confirmed the success in CNT surface modification. Results of toxicity assays showed that formation of carboxamido- and amino-functional groups indeed significantly favored the contact of MWCNTs with E. coli cells and thus caused stronger bactericidal effect. Interestingly, when MWCNT-COOH was subject to disturbance of mechanical shacking, the chance of MWCNT-COOH in contact with E. coli increased, which in turn led to increased toxicity. Together, our results indicated that in addition to surface charge, dispersivity of MWCNTs may play an equally important role in determining the antibacterial activity of suspended MWCNTs to planktonic E. coli cells. | en_US |