Figure 1. 3D hybrid matrix designs and cardiac microtissue morphology.

(a) The workflow to grow a 3D cardiac microtissue on a hybrid filamentous matrix. hiPSC-CMs were differentiated, purified, recollected and seeded onto the 3D filamentous hybrid matrices fabricated by TPP technology. hiPSC-CMs self-assembled into 3D beating cardiac microtissues. SEM image shows local fiber structure at mechanical mismatch region in a hybrid matrix. Scale bar, 50 μm. (b) Design schematics of double-hybrid matrix (DH) with half thin and half thick fibers, triple-hybrid matrix (TH) with center thin fibers sandwiched by two sides of thick fibers (TH-K), and triple-hybrid matrix with center thick fibers sandwiched by two sides of thin fibers (TH-N). (c) Representative 3D cardiac microtissues growing on DH (left), TH-K (middle) and TH-N (right) matrices. The mechanical mismatch regions (one for DH matrix design and two for TH matrix designs) are highlighted in the image insertions. Scale bars: 100 μm. Scale bar for insertions: 15 μm. Relative tissue size showed significant difference (d) between S-K and S-N matrices, (e) between thick side and thin side of the DH matrices, (f) but no difference between TH-K and TH-N matrices. Statistical analysis: two-tailed student t-test (*p < 0.05, **p < 0.005). Data is shown as mean value (n ≥ 4).