Figure 4. Stem cell response to materials with independently controlled stiffness and adhesion.

The morphological changes of cells cultured on surfaces with independently controlled stiffness and adhesion were quantified over time in terms of inverse shape ratio (perimeter²/4π*Area) and projected perimeter. Inverse shape ratio characterizes cell spreading and deviation from non-adherent circular shape. Cells were characterized on: a, low adhesion (α-CD-YRGDS) and b, high adhesion (α-CD-YRGDS) content surfaces with variable cross-linking density or mechanical properties. Larger differences in both cell shape parameters developed when the hydrogels were decorated with higher concentrations of α-CD-YRGDS nanobeads. Cell differentiation was related to cell shape, and gene expression was evaluated after 21 days of culture for markers related to c, adipogenesis, d, myogenesis, e, chondrogenesis, and f, osteogenesis. Data collected throughout the study of cell morphology is presented as a mean ± standard deviation of multiple data samples (n = 15–20), except for PEGDA samples.