Reduced graphene oxide functionalized nanofibrous silk fibroin matrices for engineering excitable tissues

Tissue engineering has provided an alternative strategy for the regeneration of functional tissues for drug screening and disease intervention. The central challenge in the development of mature and functional excitable tissues is to design and construct advanced conductive biomaterials that can guide cells to form electrically interconnected networks. The objective of this study was to develop reduced graphene oxide modified silk nanofibrous biomaterials with controllable surface deposition on the nanoscale. A vacuum filtration system was applied to attain reduced graphene oxide nanolayer deposition. The results demonstrate that with this method, a uniform and compact reduced graphene oxide nanolayer was formed, and the conductivity and nanofibrous morphology of the materials was well controlled. The composite nanofibrous scaffolds were applied for the engineering of cardiac tissues and demonstrated a great ability to promote tissue formation and functions, including the expression of cardiac-specific proteins, the formation of sarcomeric structures and gap junctions, and tissue contraction. External electrical stimulation further enhanced the maturation level of cardiac tissues cultured on these conductive scaffolds. All these results demonstrated the great potential of reduced graphene oxide functionalized silk biomaterials fabricated using our method for recapitulating electrical microenvironments for the regeneration of functional excitable tissues. The key in engineering functional excitable tissues is to develop advanced conductive biomaterials that could guide cells to form electrically interconnected networks. This study aims to develop reduced graphene oxide functionalized silk nanofibrous biomaterials with controllable surface deposition. The composites exhibit uniform nanolayer of reduced graphene oxide, and well controlled conductivity and nanofibrous morphology. The scaffolds promote formation and functionalities of engineered cardiac tissues, and electrical stimulation further enhances these promotion effects. This research provides guidance for using reduced graphene oxide to fabricate conductive nanofibrous biomaterials for the regeneration of functional excitable tissues. A biocompatible scaffold that helps cardiac cells grow into actively beating tissue has been developed by researchers centered in Xi’an, China. Feng Xu and Xiaohui Zhang from Bioinspired Engineering and Biomechanics Center (BEBC) at Xi’an Jiaotong University and colleagues deposited reduced graphene oxide, a chemically stabilized form of the single-atom thin carbon film, onto naturally stretchy silk nanofibers. After culturing cardiac muscle cells onto the hybrid scaffold, the team showed that the conductive graphene oxide coating helped the new tissue form electrically active, interconnected networks along the silk threads. This engineering strategy produced cardiac tissue healthy enough to beat spontaneously. Significant improvements in tissue beating rates and intensities were obtained when electric fields were applied during the initial cell culture. Electrical stimulation also enhanced expression of cardiac-specific proteins, and helped muscle-like tissue achieve maturity faster.