The Development of Composite Fibers as Multifunctional Wound Dressings for the Treatment of Diabetic Ulcer

In Taiwan, the amount of medical resources required for the diabetes treatment steadily increases over recent years. Diabetic ulcer is a major complication of diabetes which leads chronic wound formation. The prolonged inflammatory phase may result in not only an immature granulation tissue but also a reduction of wound tensile strength, which always eventually cause amputations. Because diabetic wounds are deeper, more exudative, and more necrotic than the normal wounds, it is essential to develop a multifunctional wound dressing to promote tissue regeneration. Our previous project (MOST 103-2221-E-008 -118 -) demonstrated that a dual jet system can coelectrospin nanofibers in arbitrary ratios. Therefore, we will apply this method to fabricate a versatile composite nanofibrous matrix. Calcium alginate and poly(lactide-co-glycolide)(PLGA) will be coelectrospun as composite nanofibers. Calcium alginate fibers can be used as highly absorbent dressings to provide a moist environment in wound sites. On the other hand, PLGA will be applied to increase mechanical strength and protein adsorption. In addition, silver nanoparticles will be embedded in PLGA fibers for long-term release to inhibit the growth of microorganism. Plasmid DNA encoding platelet-derived growth factor (PDGF) will be delivered from composite fibers because this growth factor is a chemoattractant for neutrophils and can induce the proliferation and differentiation of fibroblasts. Furthermore, collagen deposition and angiogenesis can also be promoted. These PDGF plasmids will be complexed with polyethylenimine (PEI) to form cationic nanoparticles which will be adsorbed onto anionic alginate fibers through electrostatic interaction. As wound cells adhered to composite fibers, they can be in situ tranfected to continuously express PDGF. Moreover, calcium ions in alginate fibers can be released to wound sites through ion exchange to accelerate hemostasis. These calcium-insufficient alginate fibers should gradually degrade with time to allow cell infiltration, enhance cell adhesion onto PLGA fibers, and eventually improve tissue regeneration. A co-culture system will be applied to investigate the effect of transfection on cell proliferation and activation. Because complicated pathology of chronic wounds is difficult to simulate through in vitro experiments, the healing effects of these composite nanofibrous dressings will be evaluated using diabetic mouse models. Streptozocin (STZ) will be injected to C57/BL6 mice to damage insulin-producing beta cells, and the treated mice will become type I diabetic. On the other hand, mice with strain of diabetes spontaneous mutation (Leprdb) manifest morbid obesity and eventually become type II diabetic. Full-thickness skin wounds will be created in dorsal area of these diabetic mice by biopsy punches with diameters of 8 mm, which will be covered by the composite fibers. The wound tissues will be harvested and sectioned for histology analysis. Through hematoxylin/eosin (H/E) and immunohistochemical (IHC) staining, tissue regeneration in wound sites will be evaluated. In addition, Western blot and real-time polymerase chain reaction (RT-PCR) analysis will be performed to investigate the activity of re-epithelialization, remodeling, and angiogenesis in different stages. We expect this comprehensive study provides an ideal solution to facilitate diabetic-induced chronic wounds.