Polypyrrole-coated poly(L-lactic acid-co-epsilon-caprolactone)/silk fibroin nanofibrous membranes promoting neural cell proliferation and differentiation with electrical stimulation

Polypyrrole (Ppy), as a conductive polymer, is commonly used for nerve tissue engineering because of its good conductivity and non-cytotoxicity. To avoid the inconvenience of Ppy processing, it was coated on electrospun poly(L-lactic acid-co-epsilon-caprolactone)/silk fibroin (PLCL/SF) nanofibers via the in situ oxidative polymerization of pyrrole monomers in this study. Ppy-coated PLCL/SF membranes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric (TG) analysis. The results confirmed the disposition of Ppy on the PLCL/SF nanofibers, and the nanofibers kept their nanofibrous morphology and thermal stability, in comparison to the untreated ones. The conductivities and water contact angles were evaluated as well, and indicated that the conductivity and hydrophilicity of Ppy-coated nanofibers were increased. Furthermore, this study showed that electrical stimulation (ES) promoted PC12 cell differentiation and axonal extension on Ppy-coated nanofibers. The MTT assay suggested that both Ppy and ES could promote Schwann cell (SC) proliferation. Immunofluorescence staining and real time-qPCR (RT-qPCR) testing demonstrated that ES could induce PC12 cell differentiation even without nerve growth factor (NGF) treatment, and moreover, Ppy coating increased the inducing effects on PC12 cell differentiation. The overall results indicated the promising potential of Ppy-coated PLCL/SF nanofibrous membranes for peripheral nerve repair and regeneration.