Figure 4. Focal adhesion formation on ∼350 MPa spots of varying diameter.

(A) 1 μm spots of ∼350 MPa (formed with doses of 3,000 μC/cm²) induced differential focal adhesion co-localization in hMSCs as a function of spot diameter. This effect was lost on 100 nm spots, high magnification insert of paxillin staining within the boarded area indicated in (a,b). (B) Mander's coefficient of co-localization indicated a linear increase in FA co-localization to the e-beam exposed regions with increasing spot diameter. (D) Cellular spreading was not significantly different in MSCs cultured on spots of modulated rigidity as a function of spot diameter relative to unexposed PDMS, yet significant reductions in cell spreading were noted relative to hMSCs cultured on glass control substrates. (E) Significant reductions in mean FA area were also induced by reducing the spot diameter. For statistical analysis of significance see Supplementary Table 2 and Supplementary Table 3. Results are SEM, green = actin, blue = paxillin, red = nucleus, bar = 10 μm.