Injectable, stretchable, and conductance-stable fiber for myocardial infarction repair

Injecting electroactive biomaterials into infarcted myocardium to restore blocked electrical signal pathways is an effective way for repairing myocardial infarction. However, re-establishing stable and anisotropic conductive pathways during the constant contraction and relaxation of the heart remains a challenge. Herein, inspired by the myocardial fibers with striated surfaces, a super-elastic and conductance-stable polyurethane fiber with buckled polypyrrole coating (PU150 %@PPy) was designed. The bionic composite fiber exhibited excellent stretchability (>450 %), electrical stability under large strains (Delta R/R-0 of only 0.04 at 100 % strain), and long-term durability (>1000000 cycles), enabling stable transmission of electrical signals in a beating heart. Specifically, the composite fibers could be injected into the infarct area in minimally invasive manner and aligned with the myocardial fibers to provide anisotropic conductive pathways. After injecting the PU@PPy fibers into the infarcted heart, the cardiac function was improved (33.19 % increase in fractional shortening and 38.80 % increase in ejection fraction) and the myocardial remodeling was decreased (40.30 % reduction in infarct size and 95.12 % increase in myocardial wall thickness) by re-establishing the electrical communication of the electrically separated cardiomyocytes in the infarct area as well as by providing mechanical support. The injectable, stretchable, and conductance-stable fiber offers a promising strategy for reconstructing infarcted myocardium.