Design of a Fibrin Microthread-Based Composite Layer for Use in a Cardiac Patch.

The ability to modulate the mechanical properties, and cell alignment within a cardiac patch without hindering cell functionality may have significant impact on developing therapies for treating myocardial infarctions. We developed fibrin-based composite layers comprising aligned microthreads distributed uniformly throughout a hydrogel. Increasing the microthread volume fraction (∼5%, 11% and 22%) significantly increased the moduli of the scaffolds (20.6 ± 8.1, 46.4 ± 23.0, and 97.5 ± 49.3 kPa, respectively), < 0.05. Analyses of cell-mediated contractile strains and frequencies showed no significant differences among composite layers and fibrin hydrogel controls, suggesting that microthread-based composite layers exhibit similar active functional properties. Cell orientation in composite layers suggests an increase in nuclear alignment within 100 μm of fibrin microthreads and suggests that microthreads influence the alignment in adjacent areas. In this study, we developed composite layers with tunable, mechanical patch properties that improve cell alignment and support cell functionality.