Dual delivery of growth factors with coacervate-coated poly(lactic-co-glycolic acid) nanofiber improves neovascularization in a mouse skin flap model.

Random skin flaps are commonly used in plastic and reconstructive surgery for patients suffering from severe or large scale wounds or in facial reconstruction. However, skin flaps are sometimes susceptible to partial or complete necrosis at the distal parts of the flaps due to insufficient blood perfusion in the defected area. In order to improve neovascularization in skin flaps, we developed an exogenous growth factor (GF) delivery platform comprised of coacervate-coated poly(lactic-co-glycolic acid) (PLGA) nanofibers. We used a coacervate that is a self-assembled complex of poly(ethylene argininyl aspartate diglyceride) (PEAD) polycation, heparin, and cargo GFs (i.e., vascular endothelial growth factor (VEGF) and/or transforming growth factor beta 3 (TGF-β3)). The coacervate was coated onto a nanofibrous PLGA membrane for co-administration of dual GFs. In vitro proliferation of human dermal fibroblasts and endothelial tube formation using human umbilical vein endothelial cells indicated an enhanced bioactivity of released GFs when both VEGF and TGF-β3 were incorporated into coacervate-coated PLGA nanofibers (Coa-Dual NFs). Moreover, an in vivo study using a mouse skin flap model demonstrated that implantation of Coa-Dual NF reduced necrosis and enhanced blood perfusion in skin flap areas after 10 days, as compared to any single GF-loaded coacervate/PLGA fiber (Coa-Single NF) along with direct administration of the other GF onto the defect site. Moreover, Coa-Dual NFs exhibited a well-composed skin appendage and a significantly higher number of blood vessels. Based upon these results, we conclude that Coa-Dual NFs may stimulate cellular activity by enhancing the bioactivity of the released GF, leading to a synergetic effect of dual GFs for reducing necrosis in the random skin flaps. Therefore, Coa-Dual NFs could be a valuable drug delivery platform for a variety of potential clinical applications for skin tissue regeneration applications.