hMSCs growth on swCNT monolayers. A Glass substrate was used as a control. B swCNTs were adsorbed onto the glass substrate to form a swCNT monolayer. C Oxygen plasma treatment was applied to modulate the swCNT surface properties. Adhesion and proliferation of hMSCs on various substrates. Fluorescence images of actin filaments show the morphology of hMSCs on D a glass substrate, E a swCNT monolayer, and F an oxygen-plasma-treated swCNT monolayer (O-swCNT). Scale bars are 100 μm. The quantitative analysis was visualized with g the averaged value of area per cell (number of cells, n = 200), H the averaged value of the ratio of long and short axial lengths (a/b in b; n = 200), and I the averaged MTS assay value at day 6 (n = 3). In all analyses, Student’s t test was utilized to calculate the significance (*p < 0.05).