An Injectable Conductive Three-Dimensional Elastic Network by Tangled Surgical-Suture Spring for Heart Repair.

Designing scaffolds with persistent elasticity and conductivity to mimic microenvironment becomes a feasible way to repair cardiac tissue. Injectable biomaterials for cardiac tissue engineering have demonstrated able to restore cardiac function by preventing ventricular dilation, enhancing angiogenesis, and improving conduction velocity. However, limitations are still among them, such as poor mechanical stability, low conductivity, and complicated procedure. Here, we developed thermal plastic poly(glycolic acid) surgical suture and mussel-inspired conductive particle's adhesion into a highly elastic, conductive spring-like coils. The polypyrrole (PPy) coated bio-spring acted as an electrode and then was assembled into a solid-state supercapacitor. After being injected through a syringe needle (0.33 mm inner diameter), the tangled coils formed an elastically conductive three-dimensional (3-D) network to modulate cardiac function. We found that cardiomyocytes (CMs) grew along the spring coils' track with elongated morphologies and formed highly oriented sarcomeres. The bio-spring enhanced the CMs' maturation in synchronous contraction accompanied with high expressions of cardiac-specific proteins in α-actinin and connexin 43 (cx43). After the elastic, conductive bio-springs were injected into the myocardial infarction (MI) area, the left ventricular fractional shortening was improved about 12.6% and the infarct size was decreased by about 34%. Interestingly, the spring can be utilized as a sensor to measure the CMs' contractile force, which was 1.57 х 10-3 0.26 х 10-3 mN (~ 4.1х106 cells). Accordingly, this study highlights an injectable bio-spring to form a tangled conductive 3-D network in vivo for MI repair.