Evaluation of the antibacterial activity of metal impregnated multi-walled carbon nanotubes: impact of domestic wastewater as supporting medium

Abstract

Despite the availability of potential water treatment resources, bacterial infections are still of major concern, especially in developing countries where large numbers of people do not have access to clean and safe water. Nanotechnology offers great possibilities in the field of wastewater treatment for its potency against pathogenic bacteria. This study focuses on the antimicrobial activity of three different nano-metals (silver, copper oxide, and zinc oxide) and the additive effect when they are used in the presence of functionalized multi-walled carbon nanotubes (MWCNTs) against four com - monly found domestic wastewater bacterial strains. The bacteria studied included Gram-positive bacteria ( Bacillus subtilis and Staphylococcus aureus ) and Gram-negative bacteria ( Salmonella typhi and Escherichia coli ). Silver nanoparticles (Ag NPs) were the most potent antibacterial agent reducing up to 60.78% ± 8.33% and 63.26% ± 2.12% growth of Gram-positive and Gram-negative bacteria, respectively. The effectiveness increased to 96.66% ± 1.99% against Gram-positive bacteria and 94.59% ± 1.39% against Gram-negative bacteria when the MWCNT was decorated with Ag NPs, due to the improved surface area of the synthesized complex. Additionally, it was found that the inactivation of bacteria by nanomaterials was species-specific, with Gram-negative E. coli showing the strongest overall resis- tance. The overall antibacterial effect of the synthesized compounds was stronger in real wastewater solutions while the nutrients enriched media allowed more prominent growth and bacteria recovery