(a) Mesenchymal stem cells, 24 h
(b) Osteoblast cells, 24 h
Figure 3: SEM micrographs of (a) human mesenchymal stem cells (hMSCs) and (b) osteoblast cells cultured on flat Ti and 30, 50, 70, and 100 nm diameter TiO2 nanotube surfaces after 24 h of culture (scale bar, 100 μm). Red arrows (a) and brackets (b) emphasize extraordinary cell elongation; yellow arrows indicate elongated leading edges of lamellipodia.