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.

OBJECTIVE

To compare the effect on the microcirculation in venous leg ulcers (VLUs) of two treatment regimens that promote a moist wound environment versus paraffin gauze. The hypothesis is that moist wound dressings are more likely to stimulate the microcirculation and therefore angiogenesis.

METHOD

Patients with non-healing VLUs were randomised to receive either a foam dressing (Suprasorb P), a collagen dressing (Suprasorb C) plus the foam dressing, or paraffin gauze (control). All patients wore short-stretch high compression bandages. Parameters used to measure the effects of the treatments on the microcirculation were: TcPO2 measurements, video laser Doppler measurements and the number of capillaries in the wound bed. The progression towards healing was measured by the reduction in ulcer area and formation of granulation tissue. The treatment period was four weeks.

RESULTS

Significant increases in TcPO2 values were reported between baseline and week 4 for patients receiving the foam dressing only or the collagen plus foam dressing combination (p<0.008 versus p<0.003 respectively). There was also a significant increase in the number of capillaries for the collagen plus foam treatment only (p<0.002).

CONCLUSION

This pilot study suggests that a moist wound environment stimulates perfusion of blood and oxygen to the wound tissue, thereby promoting angiogenesis. The collagen and foam dressing combination demonstrated superior results to the control and the foam dressing only. Monitoring the microcirculation may help to assess the effect of dressings on VLU healing, although more research is needed.

DECLARATION OF INTEREST

This pilot study was supported by a limited grant from Lohmann & Rauscher GmbH, Germany.