Coaxial electrospun nanofibers for treatment of diabetic ulcers with binary release of multiple growth factors

Abstract

Two different growth factors were physically and chemically loaded into a single nanofibrous matrix to increase wound healing efficacy and to obtain bi-phasic release profiles of the loaded growth factors. Amine-functionalized block copolymers composed of PCL and PEG were synthesized and subsequently co-electrospun with a bFGF solution to prepare coaxial nanofibrous meshes. The nanofibrous meshes were chemically modified with an EGF by conjugating surface-exposed amine groups of nanofibers to carboxylate groups of EGF. The characterization of a core-encapsulated bFGF and a surface-immobilized EGF by X-ray photoelectron spectroscopy revealed distinctive peaks of nitrogen atoms, which confirm the presence of a surface-immobilized EGF on the nanofiber. The release profiles of the bFGF and the EGF clearly demonstrated binary release profiles of each protein: the bFGF showed a high initial burst in 24 h, whereas the EGF showed no negligible release in 7 days. Human primary keratinocyte and fibroblast cells cultivated on the nanofibrous meshes showed the highest cellular proliferation on mesh composed of the bFGF and the EGF. In an animal study, the wound closure rates of diabetic ulcers were significantly increased in 7 days when bFGF/EGF nanofibrous meshes were administered to dorsal wound sites. The expression levels of keratinocyte-specific markers were examined by RT-PCR, and keratin 14, 5, 1 have higher expression levels than the control groups. This outcome strongly suggests that bi-phasic release of bFGF and EGF greatly supported tissue recovery with the similar phenotypes as the original keratinized tissues. A histological examination of the recovered tissue also confirms that bFGF/EGF nanofibrous meshes increase the accumulation of both collagen and a cemented matrix of keratin. Thus, the nanofibrous matrix is a promising wound dressing material that can increase wound healing rates while reducing scar formation.