Characterization of Silver-coated Carbon Nanotubes Dispersed in a Specifically Formulated Dispersant-NanoSperse AQ~R

摘要

Silver-coated carbon nanotubes (AgCNTs) are well documented for their antibacterial properties. However, aqueous dispersions of AgCNTs could be less effective against bacteria due to their tendency to agglomerate when re-suspended in water. This may be controlled by adopting different dispersion techniques for AgCNTs such as using a specifically formulated dispersant solution. In this study we have characterized AgCNTs dispersed in Nanosperse AQ (dAgCNTs) from NanoLab Inc. and water dispersed AgCNTs (wAgCNTs), and compared their bactericidal activity against Salmonella enterica serovar Typhimurium and Escherichia coli. AgCNTs were characterized using zeta potential and fourier transform infrared spectroscopy (FT-IR) analysis. dAgCNTs were homogenously dispersed as compared to wAgCNTs which formed agglomerates even after repeated sonication. The zeta potential value of dAgCNTs was-41.9mv compared to wAgCNTs (-30.7mv) indicating a higher degree of stability for dAgCNTs. FT-IR analysis of dAgCNTs showed the presence of additional peaks specific for dAgCNTs as compared to wAgCNTs. The minimum inhibitory concentrations (MIC) of dAgCNTs (31-15 μg/ml) were approximately three folds lower compared to wAgCNTs (100-62.5 μg /ml) against both Salmonella enterica serovar Typhimurium and Escherichia coli. Live/dead staining revealed that exposure to 12.5 μg /ml of dAgCNTs resulted in at least twice the number of dead bacteria as compared to exposure to similar concentrations of wAgCNTs. NanoSperse AQ did not have any antibacterial effect by itself. Our results indicate that dispersion of AgCNTs using an appropriate dispersion technique may result in a relatively stable and homogenous solution of AgCNTs, thereby improving their antibacterial activity.