Figure 27.

Magnetically actuated, cell-laden hydrogels (μMACs). Three types of masks are designed, one for each of the layers: (i) a “magnetically actuated” PEGDMA layer encapsulating magnetic Fe₃O₄ nanoparticles, (ii) a stiff, constrained layer, and (iii) a gelatin methacrylate layer encapsulating the cells. The bottom right shows a photo of the hydrogel and cells setup, scale bar = 2 mm. (B) Fluorescent confocal images (top panel) and 3D reconstructions (bottom panel) of encapsulated fibroblasts in μMACs (modulus = 6 kPa) under different strain conditions. Cellular F-actin fibers stained using phalloidin (red), and nuclei (DAPI, blue). Graphs show (left) mean cell spreading volume increase over culture time and increased strain levels, rising quickly to an asymptotic saturation level at a critical strain in the range of 40–60%, and (right) cell proliferation increases with time and strain levels, saturating at the ∼40% strain condition. Scale bars = 500 μm. Error bars, SD (n = 10 μMACs for each strain level, ∗∗P < 0.01, ∗∗∗P < 0.001). Reprinted with permission from ref (556). Copyright 2016 Nature Publishing Group.