(a) Average cumulative migration of keratinocytes on gradients g1 (quadratic), g2 (power law), g3 (linear), g5 (logarithmic) of immobilized SS-EGF (167 μg/ml) and TCPS over 7 days. (b) Average cumulative migration of keratinocytes on gradients g1 (quadratic), g2 (power law) of immobilized SS-EGF (167 μg/ml) and TCPS over 7 days. (c) Average cumulative migration of keratinocytes on immobilized SS-EGF g1 (quadratic) gradients of 0, 83, 167, 333, and 667 μg/ml SS-EGF solutions and TCPS over 7 days.