Anticancer and antibacterial properties of carbon nanotubes are governed by their functional groups

Due to their high strength, low weight, and biologically-inspired dimensions, carbon nanotubes have found wide interest across all of medicine. In this study, four types of highly dispersible multi-walled carbon nanotubes (CNTs) of similar dimensions, but slightly different chemical compositions, were compared with an unmodified material to verify the impact their surface chemistry has on cytocompatibility, anticancer, inflammation, and antibacterial properties. Minute changes in the chemical composition were found to greatly affect the biological performance of the CNTs. Specifically, the CNTs with a large number of carbon atoms with a +2 coordination number induced cytotoxicity in macrophages and melanoma cells, and had a moderate antibacterial effect against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria strains, all while being cytocompatible towards human dermal fibroblasts. Moreover, substituting some of the OH groups with ammonia diminished their cytotoxicity towards macrophages while still maintaining the aforementioned positive qualities. At the same time, CNTs with a large number of carbon atoms with a +3 coordination number had a high innate cytocompatibility towards normal healthy cells but were toxic towards cancer cells and bacteria. The latter was further boosted by reacting the CNTs' carboxyl groups with ammonia. Although requiring further analyses, the results of this study, thus, introduce new CNTs that without drugs can treat cancer, inflammation, and/or infection while still remaining cytocompatible with mammalian cells. Carbon nanotubes with carbon atoms at a +3 oxidation number easily translocate through the cell membrane. With cytotoxicity towards macrophages at 10%, cancer cell number is reduced by up to 59% and bacterial colonization - by up to 99%.

Automated summary

This study demonstrates the significant impact of surface chemistry on the biological performance of carbon nanotubes (CNTs). Minute changes in chemical composition can greatly affect the cytotoxicity, antibacterial properties, and anticancer effects of CNTs. CNTs with a larger number of carbon atoms with a +2 coordination number exhibit cytotoxicity in macrophages and melanoma cells, moderate antibacterial effects, and cytocompatibility towards human dermal fibroblasts. CNTs with a larger number of carbon atoms with a +3 coordination number show high cytocompatibility towards normal healthy cells but are toxic towards cancer cells and bacteria. The cytotoxicity towards macrophages can be reduced by substituting some of the OH groups with ammonia.