Co-axial electrospinning of PLLA shell, collagen core nanofibers for skin tissue engineering

The main functions of wound dressing biomaterials are to promote a moist environment in the wound while protecting the area from mechanical injury and microbial contamination. Furthermore, the scaffold used for skin tissue engineering must mimic epidermal and dermal layers as well as support the growth of keratinocytes and fibroblasts. In this study, PLLA (shell) and EGF-encapsulated collagen (core) nanofibers were produced by coaxial electrospinning at 25 kV potential, 12 cm collector distance, and 0.125 mL/h flow rate of PLLA (15%) and collagen (4%). The bilayer structure was produced by gelling GeIMA in between two nanofiber membranes to imitate the epidermal and dermal layers of skin. Cytocompatibility properties of nanofiber membrane and bilayer structure were characterized by mono- and coculture of keratinocytes (HaCaT) and fibroblasts (3T3), respectively. TEM revealed that the PLLA shell and collagen core thicknesses were about 60 and 115 nm, respectively. Oxygen and water vapor could pass through the GeIMA- integrated bilayer nanofiber membranes. The presence of EGF in nanofibers could increase cell proliferation. Fluorescence and SEM imaging showed that HaCaT and 3T3 could cover the membrane after 14 days of monoculture. Cocultures showed a reduction in the proliferation of cells in the first week and a recovery during the second and third weeks. In a mechanical bioreactor, cocultured bilayer membranes formed interlocked polygonal keratinocyte cells. These results showed that the bilayer nanofiber membrane and GeIMA combination provided cell compatibility. Furthermore, the use of a mechanical reactor was found to be effective in the formation of a functional keratinocyte layer by stimulating cells.