Processing and Characterization of Antibacterial Hydrogel Sheet Dressings Composed of Poly(vinyl alcohol) and Silk Fibroin for Wound Healing Application

Abstract

Hydrogels are soft materials that contain high water content within their 3-dimensional structure. Such extremely hydrated environment allows hydrogels to recapitulate the structure of many native tissues inside the body. In biomedical application, hydrogels have been extensively used as biocompatible materials, drug delivery systems, and tissue-engineered scaffolds that can be designed to possess either permanent or slow-degradation properties. In this research, we applied gamma irradiation to develop transparent and conformal hydrogel sheets with sufficient mechanical strength from poly(vinyl alcohol) (PVA) and further modified the based PVA matrix with naturally-derived silk fibroin (SF) protein and silver nitrate (AgNO3) for wound healing purpose. The physical and mechanical properties of based PVA hydrogels formed at varied irradiation doses from 10 - 80 kGy were first characterized. The dose of 60 kGy was found to be optimal to process flexible and elastic PVA sheets with equilibrium degree of swelling of 1000 %, gel fraction of 90 %, and tensile strength of 19 kPa. To further enhance water absorption capacity, 10 - 40 % (w/w) silk fibroin was added to the based PVA matrix. Based on water absorption and gel fraction data, hydrogel sheets with 8PVA:2SF formulation was selected for antibacterial test. Disc diffusion assay showed that the incorporation of 0.4 mM AgNO3 in 8PVA:2SF hydrogel sheets could inhibit the growth of Staphyllococcus aureus and Pseudomonas aeruginosa. These results demonstrated that a prototypic, antibacterial hydrogel sheet dressing composed of both synthetic and natural polymers could be developed within a single-step by gamma irradiation technique.

Cytotoxicity Evaluation of Hydrogel Sheet Dressings Fabricated by Gamma Irradiation: Extract and Semi-Direct Contact Tests

“…To this end, crosslinking by the use of high energy radiation such as gamma or electron beam provides an alternative platform to fabricate hydrogels at relatively mild conditions without the use of harmful chemical reagents [1][2][3]. Previous studies also showed that gamma irradiation could be used to effectively process cytocompatible PVAbased hydrogels containing silk fibroin [4] or silk sericin [23]. Therefore, these cytocompatibility results of bare hydrogel sheets approve both the materials and processing method, providing an important 1 st step to warrant a further biological evaluation in an animal model such as wound healing efficacy, or skin irritation patch test in a clinical trial.…”

“…The soft consistency of hydrogels enables them to mimic the structure of natural tissue and make them an attractive candidate for a wide range of biomedical applications including contact lenses, wound dressings, drug delivery systems and hygiene products [2,3]. In terms of wound dressings, hydrogels in the form of flat sheets or filler strands can be used as a protective barrier over skin lesions to absorb wound exudate and provide the appropriate moist environment that promotes natural wound healing [4][5][6][7][8].…”

Antibacterial Hydrogel Sheet Dressings Composed of Poly(vinyl alcohol) and Silver Nanoparticles by Electron Beam Irradiation

“…We then tested if such repeated irradiation would affect the swelling and mechanical properties of the hydrogels. Previously, we demonstrated that both the gel strength and tensile strength of the hydrogel sheets increased with the irradiation doses used to crosslink the hydrogels having the similar 10% (w/v) PVA system and gamma doses ranging from 25 to 80 kGy [26]. Therefore, based on our current data on swelling, hydrogel sheets that formed at 25 and 40 kGy were selected for the repeated irradiation experiments, as the swelling became saturated at higher doses.…”

“…Round hydrogel sheets from the 5.5 cm dishes were first rinsed with DI water to remove unreacted PVA. The samples were then fully immersed for 24 h in an aqueous solution containing 142 mmol NaCl and 2.5 mM CaCl 2 , which simulated the discharge at the wound site [26], before being dried at 60 • C to a constant weight. The equilibrium degree of the swelling was calculated as follows:…”