Studies on Enhancement of Anti-microbial Activity of Pristine MWCNTs Against Pathogens

Carbon nanotubes (CNTs), owing to their inherently unique properties in the domain of biomedical sciences including drug delivery, offer an exciting platform to the researchers. Of late, their applications have also been successfully established. Recently, single-walled CNTs (SWCNTs) have been explored for antibacterial efficacy, but naïve multi-walled CNTs (MWCNTs) still remained unearthed. The present studies endeavor the investigation of the potential of various non-ionic surfactants in solubility enhancement of MWCNTs and their subsequent antibacterial efficacy against Escherichia coli and Staphylococcus aureus. Polysorbates offer more solubility to MWCNTs vis-à-vis the phospholipids. However, the antibacterial effect was found to be less influenced by solubility but significantly determined by the type of surfactant. Transmission electron photomicrographs confirmed significant adhesion of MWCNTs to the bacterial walls only in the presence of unsaturated phospholipids and this was expressed in the form of lowest minimum inhibitory concentration (MIC) values of MWCNTs dispersed with the same. The findings are unique as MWCNTs were found to be active against both Gram-negative and Gram-positive bacteria to a similar extent, though somewhat milder than SWCNTs. However, when dispersed with unsaturated phospholipids, the former offer almost comparable antibacterial effects to that of the latter. The study opens a new research domain to further explore the antibacterial effects of non-functionalized and relatively safer MWCNTs, accentuating the importance of biocomponents like unsaturated phospholipids in this purview.