FIG. 4.

Neurite growth anisotropy in experiments with IKVAV-grafted collagen with a 5-mm cross-channel (A), and a 3-mm cross-channel (B). Each point represents the average length of neurites extending up the gradient and down the gradient from a single network±standard error of the mean (SEM). For conditions where no gradient was present, the direction with longer average growth was plotted as the ordinate value. The dashed line represents perfectly symmetric growth. In no case was growth perfectly uniform, though in control conditions, the points fell close to the dashed line. In gradient conditions, only the shallow gradients produced with 50% IKVAV-grafted collagen as the source across a 5-mm channel appeared to consistently bias growth up the gradient of adhesion. The experiments were further quantified to determine the average relative growth bias (Table 2) and average total length (Fig. 7).