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

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