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Chronic wounds contain elevated levels of proteases, proinflammatory cytokines, and free radicals. The presence of bacteria further exaggerates the tissue-damaging processes. For successful treatment, the wound dressing needs to manage wound exudates, create a moist environment, inhibit infection, bind pathophysiological factors that are detrimental to wound healing, and provide thermal isolation. Furthermore, it has to relieve pain, be easy to use, show no allergic potency, and not release toxic residues. The present study suggests a comprehensive in vitro approach to enable the assessment of wound dressings to support optimal conditions for wound healing. Three alginate-based wound dressings: alginate alone, alginate containing ionic silver, and alginate with nanocrystalline silver, were tested for biocompatibility, antimicrobial activity, and influence on chronic wound parameters such as elastase, matrix metalloproteases-2, tumor necrosis factor-alpha, interleukin-8, and free radical formation. Alginate was found to bind considerable amounts of elastase, reduce the concentration of proinflammatory cytokines and inhibit the formation of free radicals. Furthermore, alginate showed antibacterial activity and high biocompatibility. Incorporation of silver into alginate fibers increased antimicrobial activity and improved the binding affinity for elastase, matrix metalloproteases-2, and the proinflammatory cytokines tested. Addition of silver also enhanced the antioxidant capacity. However, a distinct negative effect of silver-containing alginates on human HaCaT keratinocytes was noted in vitro.

Wound healing is compromised by critical colonization and infection with bacteria. Hence, antimicrobial agents are used clinically to decrease the bacterial load and promote wound healing. Polihexanide (PHMB) has been found to be effective against a broad spectrum of micro-organisms and is increasingly utilized in rinsing solutions or in combination with wound dressings because of its good biocompatibility. In the present study, a co-culture of human keratinocytes and Staphylococcus aureus was established to serve as an in vitro model for infected wounds. Incubation of keratinocytes with increasing concentrations of S. aureus led to a dose-dependent decline of cell viability and proliferation. Lactate dehydrogenase release and interleukin-8 liberation were found to be elevated under these conditions. Polihexanide dose-dependently was able to protect keratinocytes from bacterial damage and re-establish normal human cell proliferation in vitro. Furthermore, a dressing consisting of biocellulose derived from Acetobacter xylinum with the addition of polihexanide was adept to safeguard keratinocytes against S. aureus. In conclusion, the co-culture system presented embodies a valuable tool as a model system for infected cells in a non-healing wound. Furthermore, the results obtained support the favorable function of polihexanide in the treatment of infected chronic wounds.

Infection may lead to the formation of a chronic wound or is a common complication during their treatment. Rather than relying on just debriding and cleansing the wound, additional therapeutic strategies are commonly applied in an attempt to prevent infection. Therefore, wound dressings combined with antimicrobial agents such as silver, povidine iodine, or polihexanide are increasingly utilized in the treatment of critical colonized or infected chronic wounds. Polihexanide is regarded first choice as therapy option because of its good skin tolerance beside its antimicrobial effects. Furthermore, a positive influence of polihexanide on wound closure was observed in a study with aseptic wounds in piglets. Moreover, polihexanide is able to induce cell proliferation in vitro. In vitro test systems provide valuable tools in the study of substance or material effects on cells. They use highly defined culture conditions and avoid the complex mechanisms which occur in vivo and thus allow the direct measurement of the influence on cell viability and proliferation. For instance, the anti-oxidative effect can be determined and the antimicrobial activity measured in vitro. Furthermore, a co-culture system of HaCaT keratinocytes and Staphylococcus aureus was used to test the capacity of polihexanide to protect the cells from the bacterial damage. Although antiseptics have a lower potency to induce bacterial resistance than antibiotics, concerns have been expressed regarding the overuse of antiseptics and the possible emergence of bacterial adaptation. Hence, an experimental system using microplatelaser-nephelometry was employed to test the adaptation capacity of Staphylococcus aureus during repeated treatment with polihexanide.

Wound care provides many challenges but none moreso than the management of high levels of exudate. The challenge is not only to be cost-effective and prevent maceration, but to improve the quality of life for the patient. Chronic wound fluid can be damaging to the wound healing process giving an added problem. This article examines the properties of Flivasorb® (Activa Healthcare), a wound dressing containing super absorbent polymer particles which not only absorbs high levels of exudate, but can retain the damaging particles in exudate, locking them inside the dressing.

Exudate can be an excellent indicator of what is happening within a wound and, therefore, provides valuable information during patient assessment. The volume, consistency, and particularly odour and colour, of any exudate will inform the practitioner about bacterial contamination, infection and stage of healing (Hampton and Collins, 2003). However, in the chronic wound, exudate must be effectively managed if the optimal moist environment necessary for wound healing is to be created, the negative effects of chronic exudate on fibroblasts are to be avoided (Phillips et al, 1998), and the surrounding skin protected from the risks of maceration (White, 2006). It is, therefore, important to understand chronic exudate and its effects so that appropriate treatment for the wound and peri-wound area is provided. Flivasorb® (Activa Healthcare) dressings, which include superabsorber particles, can absorb the exudate and retain it firmly within the dressing, ensuring that the potentially damaging chronic wound exudate does not reflect back onto the wound, causing maceration. This article will describe the role of exudates in wound healing, the problems associated with chronic wound exudates and how Flivasorb dressings with superabsorbent particles can provide an optimum healing environment in highly exuding wounds.