Development of a silk protein based wound dressing and its effect on wound healing in rats

Abstract

Silk has been used in textile production for centuries and in medicine, as sutures for decades. Sericin and fibroin are the two primary silk proteins. Silk has been shown to improve wound healing. Copper ions have also been documented to have healing properties. The novel silk protein based wound dressing donated by Southern Formulations (Pty) Ltd. for evaluation contains sericin, fibroin and copper ions. The aim of this study was to investigate the effect of silk proteins and copper ions combined in the form of a novel silk protein based wound dressing on burn wound healing. In the current thesis the effect of this novel silk protein based wound dressing on wound healing was investigated first by evaluating whether the dressing was cytotoxic. After determining its cytotoxicity a Wistar rat burn wound was established and utilized to investigate the effect of the novel silk protein based wound dressing on wound healing. Its effect was evaluated at the site of the wound as well as on a systemic level. The novel silk protein based wound dressing’s cytotoxic effect was evaluated on a human fibroblast primary cell culture by exposing the cells to serial dilutions of an extract prepared from the dressing. The results indicated that the novel silk protein based wound dressing is not cytotoxic up to a concentration of 25 mg/μl. No IC50 value could be found. The Wistar rat burn wound model was established with Butorphanol as part of the analgesic regimen. Histological investigation, by means of H&E and Masson’s Trichrome staining, showed that the novel silk protein based wound dressing improves epithelialization and neovascularization. On a systemic level the novel silk protein based wound dressing decreased the inflammatory process significantly. This was determined by white blood cell counts of blood smears prepared from the blood samples taken from the treatment group. The white blood cell count of the treatment group was compared with that of the control group. The white blood cell counts also showed that the dressing did not initiate an allergic response. It was also determined whether the novel silk protein based wound dressing has an impact on fibrin network architecture in circulating plasma, and whether a local burn injury treated with the novel wound dressing will change clot ultrastructure. This was evaluated by scanning electron microscopy of fibrin networks created from the rat platelet rich plasma prepared from the treatment group and compared with that of the control group. The results indicated that the novel silk protein based wound dressing did not affect clot ultrastructure. It is therefore concluded that the novel silk protein based wound dressing, containing copper ions and silk proteins sericin and fibroin, improves the formation of granulation tissue by improving epithelialization and neovascularization. It is also concluded that inflammation is statistically significantly decreased in the group of rats treated with the novel silk protein based wound dressing. Additionally, the novel silk protein based dressing does not cause an allergic reaction after primary exposure and does not change fibrin network formation or clot ultrastructure.