The Addition of Carbon Nanotubes Modifies the Biological, Physicochemical, and Electrical Properties of Carbon Nanofiber Composites

In this study, we report the fabrication of carbon nanofiber (CNF) - carbon nanotube (CNT) nanofibrous com-posites obtained by thermal treatment of an electrospun polyacrylonitrile precursor. Four types of CNTs of similar sizes but different surface functional groups were used: highly oxidized (HO, CNT composed of carbon of mainly a + 3 oxidation number) and low oxidized (LO, CNT composed of carbon of mainly a + 2 oxidation number) and two types of amidized CNTs derived from the oxidized ones (HNH and LNH, respectively). CNTs affected the structure and chemical composition of the CNF composites. All of the materials were hydrophobic, and their electrical conductivities varied from 317 [S/m] (CNF + HNH) to 542 [S/m] (CNF). The obtained nanofibers were cytocompatible (at day 7, the viability of cells was above 89 %) and revealed strong bactericidal properties towards Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria strains (reduction from 11 % for CNF to 84 % for CNF + HNH). The presence of CNTs improved the antibacterial performance and the strongest effects were observed for the HO and HNH -CNTs composed of carbon of mainly a + 3 oxidation number that had the highest sharing of quaternary nitrogen atoms, suggested to have bactericidal properties. In summary, in this study highly electrically conductive, cytocompatible, and antibacterial CNF-CNT composites were obtained. These materials could serve as scaffolds for long-term in vitro cultures or as a new class of wearable electronics among numerous other biomaterial applications.