Fig. 4: Cell protection from mechanical damages in shell-hardened macroporous hydrogels under dynamic deformations.

a FESEM images show encapsulated cells in shelled macropores (left), while the illustration depicts cell protection during continuous compression-relaxation cycles using SP hydrogels (right). Each experiment was repeated 3 times independently with similar results. Optical images (b) and strain signals (c) of continuous compression-relaxation applied to hydrogels. MC3T3-E1 cells in hydrogels identified by live/dead staining (green/red) and against ROS staining (blue) after 1500 compression-relaxation cycles at low (d) and high (e) matrix elasticities. A space of 1272 μm × 1272 μm × 400 μm in each sample was scanned layer by layer, and the images were projected onto the z-axis to show the staining. Cell viabilities (f) and normalized ROS intensities (g) of MC3T3-E1 cells encapsulated in different hydrogels after 1500 cycles of compression and relaxation. Values represent the mean and the standard deviation (n = 3 independent experiments). The p-values for NN and SP hydrogels at low concentration under strains of 0%, 30%, and 60% are 0.3005, 0.0127, and 0.0118, respectively, in (f), and 0.0039, 0.0041, and 0.0203, respectively, in g. At high concentration, the p-values for NN and SP hydrogels under strains of 0%, 30%, and 60% are 0.0037, 0.0002, and 0.00001, respectively, in (f), and 0.0012, 0.0439, and 0.0285, respectively, in (g). Statistical significance was determined by two-tailed t-test. NS: P > 0.05; *P < 0.05; **P < 0.01; ***P < 0.001.