A Novel Wound Dressing Based on Ag/Graphene Polymer Hydrogel: Effectively Kill Bacteria and Accelerate Wound Healing

High-strength bioactive glass-ceramic A-W was soaked in various acellular aqueous solutions different in ion concentrations and pH. After soaking for 7 and 30 days, surface structural changes of the glass-ceramic were investigated by means of Fourier transform infrared reflection spectroscopy, thin-film x-ray diffraction, and scanning electronmicroscopic observations, in comparison with in vivo surface structural changes. So-called Tris buffer solution, pure water buffered with trishydroxymethyl-aminomethane, which had been used by various workers as a "simulated body fluid," did not reproduce the in vivo surface structural changes, i.e., apatite formation on the surface. A solution, ion concentrations and pH of which are almost equal to those of the human blood plasma--i.e., Na+ 142.0, K+ 5.0, Mg2+ 1.5, Ca2+ 2.5, Cl- 148.8, HCO3- 4.2 and PO4(2-) 1.0 mM and buffered at pH 7.25 with the trishydroxymethyl-aminomethane--most precisely reproduced in vivo surface structure change. This shows that careful selection of simulated body fluid is required for in vitro experiments. The results also support the concept that the apatite phase on the surface of glass-ceramic A-W is formed by a chemical reaction of the glass-ceramic with the Ca2+, HPO4(2-), and OH- ions in the body fluid.

Wound dressings that can be formed in situ offer several advantages over the use of preformed dressings such as conformability without wrinkling or fluting in the wound bed, ease of application and improved patient compliance and comfort. Here we describe such an in situ forming hydrogel wound dressing from gelatin, oxidized alginate and borax. Periodate oxidized alginate rapidly cross-links proteins such as gelatin in the presence of borax to give in situ forming hydrogels that are both non-toxic and biodegradable. The composite matrix has the haemostatic effect of gelatin, the wound healing-promoting feature of alginate and the antiseptic property of borax to make it a potential wound dressing material. The hydrogel was found to have a fluid uptake of 90% of its weight which would prevent the wound bed from accumulation of exudates. The water vapour transmission rate (WVTR) of the hydrogel was found to be 2686+/-124 g/m2/day indicating that the hydrogel can maintain a moist environment over wound bed in moderate to heavily exuding wound which would enhance epithelial cell migration during the healing process. The wound healing efficacy of hydrogel was evaluated in experimental full thickness wounds using a rat model which demonstrated that within 2 weeks, the wound covered with gel was completely filled with new epithelium without any significant adverse reactions. These in situ forming hydrogels fulfil many critical elements desirable in a wound dressing material.