Illustration of the whole process from scaffold fabrication to cell culture over it. Conventional photolithography was applied for catalyst patterning and carbon nanotube growth. A transparent quartz wafer was used for optical observation. Fibronectin was coated to form an extracellular matrix layer before cell culture. Human neuroblastoma cells were cultured and differentiated over the scaffold.
Scanning electron microscope images of multiwalled carbon nanotube pillars directly grown from prepatterned surfaces. The height of each pillar is about . [(a) and (b) Dot-patterned nanotube pillars with width for each. The intervals between nanotube pillars are . Because of high aspect ratio, all pillars were slightly bent. [(c) and (d)] Dash-patterned nanotube pillars with length and width. The interval between pillars is . [(e) and (f)] Square-patterned nanotube pillars with scale.
Scanning electron microscopy images of cells over a bare surface and nanotube pillar scaffolds. The right-row images were the magnification of the positions marked by white arrows in the left-row images. [(a) and (b)] A cell over a flat bare surface. Several filopodia were extruded from the cell for companion tracking between cells. [(c) and (d)] A cell colony over the square pattern. Each cell shows a shrunken form without wide spread as if the colony was developed without enough surface adhesion. (e) A cell colony over the dot pattern. The feature of each cell is quite similar with cells in (c). (f) Two short filopodia are pulling a nanotube pillar to the direction of the colony body by strong attachment to the pillar.
SK-N-BE(2) cells on the dash pattern. (a) A merged image consists of several electron microscope images showing the full trace of a cell and extremely long filopodia protruding from the cell body (downward) and zigzag-type filopodia networking between pillars (upward). The length of the lower filopodia is longer than . [(b)–(d)] Local magnified images of the position indicated by arrows with numbers 1, 2, and 3, respectively, showing unique branching of filopodia approaching the sidewalls of the nanotube pillars. (d) A wide coverage of front upper half of the nanotube pillar by an expanded and branched filopodium.
Long extension of a cell judged from the remnant cytoskeletal structure connecting several nanotube pillars. Several filopodia protrude around the cell body. Interestingly, some filopodia connected only nanotube tips. (a) SEM image of the whole cell body. The three white tetragons are magnified 150 times in (b)–(d). (b) Abnormal branching of a filopodium approaching the tip of a nanotube pillar. The filopodium branched several times until its thickness was close to that of a single nanotube, which is about . (c) Sharing of pillar tips by two approaching and branching filopodia. (d) Widening of a filopodium touching or passing by the tip of a nanotube pillar.
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