Extended Data Fig. 1: Material synthesis and characterization.
a. Collagen is modified with norbornene using NHS and gelled at 37 °C with T cells. A low MW divalent crosslinker containing two methyltetrazines is diffused into gels at room temperature until equilibrated with the surrounding solution, to achieve even distribution within the gel. Subsequently increasing the temperature allows covalent crosslinks to form between norbornene and methyltetrazine functionalities. b. Comparison of Young’s moduli for soft and stiff gels to those of published different soft tissues. Data represents minimum, maximum, and mean. c. Stress relaxation profiles of fast relaxing and slow relaxing, soft (left) and stiff (right) collagen matrices. Values are normalized to initial modulus after deformation is applied. d. SHG images for 2 mg/ml fast relaxing and slow relaxing collagen gels. e–g. Quantification of fiber length (e), waviness (f) and angle between fibers (g) for fast and slow relaxing matrices. Data are mean ± s.e.m. for (e) n = 20, (f) n = 10, and (g) n = 20 biological samples. P-values were determined by performing two-tailed unpaired t-test. h–i. Storage and loss moduli determined using nanoindentation on collagen matrices. Data are mean ± s.e.m. P-values were determined by performing two-tailed unpaired t-test for n = 4 to n = 10 indents.
