FIG. 3.
Effects of gel stiffness on HDF's growth rate. (A) Phase-contrast images of HDFs positively stained by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide reagents. Images were captured after 14 days of cell culture. HDFs were encapsulated in collagen–PEGDE gels with varying MPEG-COL of 0 (A-1), 0.33 (A-2), and 0.67 (A-3). (B) Changes in the number of HDFs remained metabolically active in the hydrogels over 14 days. The cellular metabolic activity measured at each time point was normalized to the metabolic activity characterized right after cell encapsulation. All values are mean±standard deviation of three different samples per condition. (C) The cell growth rate, characterized with a slope of the relative cell viability versus cell culture period curve, was inversely related to the elastic modulus (E) of the hydrogel. Statistical significance of the cellular growth rate in the hydrogel with E of 0.7 kPa, relative to cellular growth rates in the hydrogel with E of 1.6 and 2.2 kPa (*p<0.05). Color images available online at www.liebertpub.com/tea