Effects of O2 and N2/H2 plasma treatments on the neuronal cell growth on single-walled carbon nanotube paper scaffolds

► The O2 and N2/H2 plasma-chemical functionalization caused changes in the surface charge states with functional groups with positive and negative charges, respectively. ► The chemical functionalization and the increased surface roughness enhanced neuronal cell adhesion, mitochondrial membrane potential, and the level of neurotransmitter in vitro. ► The cell adhesion and mitochondrial membrane potential on the negatively charged SWCNT papers were improved more than on the positively charged SWCNT papers. ► An enhanced acetylcholine level on the negatively charged SWCNT papers was observed compared to the positively charged SWCNT papers.