Fig. 3. Thermoreversibility, self-healing, bioprinting and tunable stress-relaxation of DyNAtrix.
a, Crosslinking efficiency of DyNAtrix (1% (w/v) P5 with different CCLs) as a function of temperature. Crosslinking efficiencies were calculated from the affine network model (Supplementary Note 2.3 and Supplementary Fig. 8). Data are shown as mean ± s.d. (n = 2). b, Self-healing of DyNAtrix (1% (w/v) P5 crosslinked with CCL-4) was confirmed by repetitive strain recovery tests alternating between 1,000% strain (breaking period, b) and 10% strain (healing period, h). When 1,000% strain is applied, DyNAtrix liquefies, as revealed by a drastic drop of its stiffness (G′ ≪ G″) and increase of the phase angle from 3° ± 1° to 74° ± 1°. DyNAtrix showed over 95% of recovery after 10 consecutive breakage–recovery cycles. c, Scheme of extrusion printing (left) and photographs of DyNAtrix being extruded from a narrow tip (right; the arrow marks the extruded gel; compare Supplementary Video 1). The gels were prepared with 1% (w/v) P5 crosslinked with CCL-64. d, A grid printed on a BioScaffolder with a total height of ~500 μm. The material was stained with SYBR Gold for imaging purposes. e, Scheme of SRCs with variable overlap domains (green). The corresponding DNA sequences are shown in Supplementary Table 1. f, Normalized stress-relaxation curves of DyNAtrix crosslinked via different SRCs (green traces) covering the typical range of biological tissues21 (yellow background). The shear stress (σ) was recorded over time at a fixed strain of 15%. Stress relaxation times (τ) were determined by the simple Maxwell model, σ(τ) = σ0/e, where σ0 is the shear stress measured at the earliest time point and e is Euler’s number. The measurements were carried out at 37 °C.