Electrohydrodynamic 3D printing of layer-specifically oriented, multiscale conductive scaffolds for cardiac tissue engineering.

Mimicking the hierarchical microarchitecture of native myocardium in vitro plays an important role in cardiac tissue engineering. Here we present a novel strategy to produce multiscale conductive scaffolds with layer-specific fiber orientations for cardiac regeneration by combining solution-based and melt-based electrohydrodynamic (EHD) printing techniques. Polycaprolactone (PCL) microfibers were printed by melt-based EHD printing and the fiber orientation was flexibly controlled in a layer-by-layer manner according to user-specific design. The as-printed microfibrous scaffolds can provide the seeded cells necessary contact cues to guide layer-specific cellular alignments. Sub-microscale conductive fibers were simultaneously incorporated inside the well-organized PCL scaffolds by solution-based EHD printing, which significantly improved the conductivity as well as the cellular adhesion and proliferation capacity. The multiscale conductive scaffolds can further direct the multiple-layer alignments of primary cardiomyocytes and facilitate cardiomyocyte-specific gene expressions, which exhibited enhanced synchronous beating behavior compared with pure microfibrous scaffolds. It is envisioned that the proposed hybrid EHD printing technique might provide a promising strategy to fabricate multifunctional micro/nanofibrous scaffolds with biomimetic architectures, electrical conductivity and even biosensing properties for the regeneration of electroactive tissues.