Self-Growing Conductive Hydrogels Establish Volumetric Biointerfaces for Cardiac Conduction Restoration

Restoring three-dimensional electrical conduction in infarcted myocardium remains a critical challenge, as conventional conductive hydrogel patches largely remain surface-confined and prevent electrical coupling of residual cardiomyocytes within fibrotic scars. Here, we present a self-growing conductive volumetric interface (SCOVE) that transforms surface-confined biointerfaces into tissue-integrated, three-dimensional conductive networks. SCOVE is delivered as an injectable hydrogel precursor containing the tissue-permeable conductive monomer 3,4-ethylenedioxythiophene-acetic acid sodium salt (ETE), which rapidly infiltrates infarcted myocardium and undergoes endogenous glucose-triggered oxidative polymerization to self-grow a conductive polyETE network in situ. The resulting hydrogel gels within 1 min, reaches cardiac-mimetic conductivity (∼1 S m^{- 1}) within 45 min, and preserves native myocardial mechanics without inducing tissue stiffening. In a rat myocardial infarction model, SCOVE penetrates the infarct, reduces scar resistivity by 2.54-fold compared with conventional 2D conductive patches, restores electrical coupling among residual cardiomyocytes, enhances Cx43 expression, and accelerates impulse propagation. By replacing static, surface-confined conductive patches with self-growing volumetric biointerfaces, this work establishes a generalizable strategy for reconstructing tissue electrophysiology and advancing bioelectronic therapies for myocardial infarction and other electrically dysfunctional tissues.