Design And Development Of Newly Foam Dressing Using In Negative Pressure Wound Therapy With Instillation And Evaluation Of Its Treating Effects On Infected Wounds

BackgroundNegative pressure wound therapy (NPWT) is an effective method to manage complicated wound. Granulation tissue into the foam and difficulties in cleaning exudation through the foam leads to common complications including pain, bleeding, infection. In order to reduce the complications, negative pressure wound therapy with instillation (NPWTi), which combines the benefits of wound cleaning effects of solutions with the advantages of NPWT, was applied. Reports have shown that, to some extents, NPWTi can remove bacteria and exudation in wound bed and foam. However, since the traditional foam dressing was still used when NPWTi was applied. The disadvantage of traditional foam dressing, such as the heterogeneous distribution of flushing pipe (which contributes to short-circuit of solutions) may hamper the treating effects of NPWTi In order to deal with this problem, we design a new foam dressing for NPWTi and using a Staphylococcus aureus infected animal model to measure the effects of newly designed foam dressing on Staphylococcus aureus, innate immunity and wound healing in this study.Objective:1. To analyze the problems of the sponges in NPWTi and develop a new sponge which could realize the uniform distribution of tubes in foam and clean wound comprehensively and reduced the pore size of foam to avoid penetration of tissues.2. Infected soft-tissue wound was built and influence mechanisms of negative pressure wound therapy with instillation on this infection model regarding the Staphylococcus aureus proliferation, gene expression of virulence factors, innate immunity and wound healing were studied.Methods1. Polyvinyl alcohol and polyurethane wound sponges were analysed. A new layered and various pore sized sponge with the hydrophobic polyurethane was developed. Tubes were inserted in sponges, which could help deliver irrigating solution to the edge of the sponges.2. Staphylococcus aureus infected soft-tissue wounds were made on the back of the pigs. Animals were grouped by different treatments including gauze, NPWT and NPWTi (new foam dressing). Analysing the effects regarding the Staphylococcus aureus proliferation, gene expression of virulence factors, innate immunity and wound healing.Results1.The change of pore size in polyurethane wound sponge was less than that in polyvinyl alcohol wound sponge.2. Comparing with gauze and NPWT, NPWTi could significantly reduce bacteria bioburden and depth of invasion. Eap, spa, hla and agrA expression and related proteins were less in NPWTi group comparing with gauze group and NPWT group. NPWTi could regulate accumulation of polymorphonuclear and IL-1β, IL-8, IL-10, TNFα, VEGF and bFGF expression comparing with gauze group and NPWT group.ConclusionNewly designed foam dressing can effectively reduce Staphylococcus aureus bioberden and inhibit virulence regulated gene expression when applied in NPWTi approach. Excessive inflammatory reaction can be inhibited and innate immunity can be active through regulating inflammation relative gene expression. Moreover, this new foam dressing can promote new blood vessel and granulation tissue.