Topical administration of growth factors has been suggested as a promising strategy for promoting the healing process and skin regeneration in wound management. However, several restrictions hinder their successful clinical use; specifically, limited percutaneous absorption causes inconsistent efficacy, and various growth factors with specific functionalities are required at different stages of healing. To overcome these shortcomings, previously we have constructed highly skin-permeable analogues of epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), and platelet-derived growth factor-A (PDGF-A) (LMWP-EGF, LMWP-IGF-I and LMWP-PDGF-A) by genetically conjugating the low-molecular-weight protamine (LMWP) to their N-terminus. In the present study, we determined the optimal concentration ratio of these growth factors by investigating In Vitro cell proliferation and the scratch wound repairing assay. After confirming synergetic effects of growth factors in combinations, we developed a topical delivery system consisting of a nanoemulsion (NE)-dispersed polyvinylpyrrolidone hydrogel loaded with all three growth factors. In Vitro permeability studies were also performed to assess whether the LMWP-conjugated growth factors in the formulation enhanced their skin permeation compared to native growth factors. Combinations of native or LMWP-fused growth factors significantly promoted fibroblast proliferation and scratch wound recovery, and the synergy of LMWP-EGF, LMWP-IGF-I and LMWP-PDGF-A was optimal at a ratio of 100:100:10 by concentration. The growth factor combination-loaded NE appeared to be spherical under cryo-transmission electron microscopy and the average droplet diameter was 127±4.30 nm. The LMWP-conjugated growth factors allowed significantly higher skin permeation than native growth factors from the NE-dispersed hydrogel. Thus, the LMWP-conjugated growth factor combination-loaded NE-dispersed hydrogel is expected to induce more rapid and prolonged wound healing.
Keywords: Growth Factor Combination; Topical Delivery; Nanoemulsion; Wound Healing; Skin Permeation.