Orientation and elongation of cells on the nano-patterns.

<p>NIH-3T3 fibroblasts on nano-patterns were investigated based on their elongation and orientation following two indices to validate the contact guidance effect from various densities of nano-patterned surfaces. <b>(A)</b> Definition of the indices for cell body orientation and elongation. Orientation angle, <i>θ</i>, is the angle between the nano-pattern and longitudinal length of the cell body. Elongation index, <i>E</i>, is the aspect ratio of the long axis to the short axis of the cell body. <b>(B)</b> Orientation angle and elongation index of cells on the various nano-patterns: 1:1, 1:2 and 1:5 nano-pattern ratios and control (no-pattern). Cellular shape was captured using a microscope at 12 and 24 hours after cell seeding. Average values of <b>(C)</b> orientation angle, <i>θ</i>, and <b>(D)</b> elongation index, <i>E</i> (n = 30, *p < 0.05 and **p < 0.01).