PVDF-Modified Graphene Nanosheets as a Piezoelectric\nand Electroconductive Bilayer Platform for Cardiac Cell Stimulation

The\nconductive microenvironment and pulsatile electromechanical\ncues in the native myocardium tissue regulate biological responses;\nhence, advanced nanomaterials must be developed to construct cardiac\ntissue-like constructs. In this work, we present a stretchable, electroconductive,\nand piezoelectric biphasic layered structure based on bilayer graphene\nnanolayers (BGF) modified polyvinylidene fluoride (PVDF) nanofibers\nto provide suitable electrophysiological microenvironments for the\nmodulation of H9c2 embryonic rat cardiomyoblasts toward cardiomyocyte-like\nphenotypes. High-quality BGFs were synthesized by chemical vapor deposition,\nand PVDF nanofibrous webs were prepared by electrospinning. We demonstrate\nthat the bilayer graphene nanosheets not only enhance the conductivity\nand piezoelectricity properties of PVDF nanofibers but also promote\ncardiomyocyte-like phenotypes by providing nanotopography cues. The\nBGF/PVDF biphasic layered structure (170 ± 15 μm thickness)\nprovides an electrical conductivity of 2.82 μS/cm and a piezoelectric\nvoltage of 0.47 mV/N, making it a suitable platform for cardiac cell\nstimulation under pulsatile electrical stimulation. Immunofluorescence\nstaining analysis determines that the mechanism of graphene influence\nis associated with enhanced structural organization and expression\nof sarcomeric α-actinin (the cardiac-specific marker for H9c2\ncells). Our results indicate that the synergistic effect of electroconductive\n(graphene) and piezoelectric (PVDF) nanomaterials provides a promising\nstrategy for developing functional cardiac-like tissue substitutes,\nwhich can be used as an efficient tool for in vitro cardiac models\nfor drug testing and screening.