Strain-Driven Topological Reorganization in Soft Fibrin Nanofibrous Networks Enabling Tissue-Like Alignment

Programming long-range anisotropy within soft, cell-laden natural nanofibrous matrices remains a central challenge in soft matter and tissue engineering, as most alignment strategies rely on external templates or non-physiological fields. Here, we demonstrate a gelation-coupled strain-induced alignment strategy that generates stable anisotropy in fibrin matrices by applying uniaxial deformation during a transient fibrillogenesis window. In partially crosslinked fibrin, stretching induces rapid fibril reorientation and pore elongation along the principal strain direction, with alignment saturation observed near 1.6× elongation under the present gelation and loading conditions. Structural and rheological analyses suggest that this post-unloading alignment arises from balanced fibril mobility and network connectivity during gelation, while a simplified pore-straightening model helps explain the observed strain-saturation behavior. This strain-guided response is further extended to uniaxial and multilayer tissue-scale constructs by tuning scaffold geometry and boundary-defined deformation. Aligned matrices improve cardiomyocyte structural organization, anisotropic contraction, electrical responsiveness, and calcium-handling kinetics, with further functional enhancement achieved by integrating a deformable piezoelectric scaffold. These results establish a simple and biologically compatible strategy for generating directionally functional fibrin-based tissues through gelation-stage mechanical reorganization.