Current Trends in Advanced Alginate-Based Wound Dressings for Chronic Wounds

Chronic wounds represent a major public health issue, with an extremely high cost worldwide. In healthy individuals, the wound healing process takes place in different stages: inflammation, cell proliferation (fibroblasts and keratinocytes of the dermis), and finally remodeling of the extracellular matrix (equilibrium between metalloproteinases and their inhibitors). In chronic wounds, the chronic inflammation favors exudate persistence and bacterial film has a special importance in the dynamics of chronic inflammation in wounds that do not heal. Recent advances in biopolymer-based materials for wound healing highlight the performance of specific alginate forms. An ideal wound dressing should be adherent to the wound surface and not to the wound bed, it should also be non-antigenic, biocompatible, semi-permeable, biodegradable, elastic but resistant, and cost-effective. It has to give protection against bacterial, infectious, mechanical, and thermal agents, to modulate the level of wound moisture, and to entrap and deliver drugs or other molecules This paper explores the roles of alginates in advanced wound-dressing forms with a particular emphasis on hydrogels, nanofibers networks, 3D-scaffolds or sponges entrapping fibroblasts, keratinocytes, or drugs to be released on the wound-bed. The latest research reports are presented and supported with in vitro and in vivo studies from the current literature.

In vitro measurements of burn dressing adherence and the effect of interventions on reducing adherence

PURPOSE

There is a paucity of research on reducing dressing adherence. This is partly due to lack of an in vitro model, recreating the clinical variability of wounds. Previously we described an in vitro gelatin model to evaluate adherence in a standardized manner. We present evaluation of strategies to reduce adherence in six dressings.

PROCEDURES

Dressing materials used were: PET (Control), fine mesh gauze coated in bismuth and petroleum jelly (BIS), nanocrystalline silver (NS), wide mesh polyester coated in polysporin ointment (WM), fine mesh cellulose acetate coated in polysporin ointment (FM), and soft silicone mesh (SIL). The dressing material was applied to gelatin and incubated for 24h. Adherence was tested using an Instron 5965 force-measurement device. Testing was repeated with various adherence reducing agents: water, surfactant, and mineral oil.

RESULTS

Adherence from least to greatest was: SIL, NS, BIS, WM, FM, PET. Water reduced adherence in all dressings; the effect increasing with exposure time. Surfactant reduced adherence of NS. Mineral oil effectively decreased adherence of BIS, and WM.

CONCLUSION

This model allows for reproducible measurement of dressing adherence. Different interventions affect various dressings. No single intervention optimally decreases adherence for all dressings.

Topical antimicrobials for burn wound infections

Throughout most of history, serious burns occupying a large percentage of body surface area were an almost certain death sentence because of subsequent infection. A number of factors such as disruption of the skin barrier, ready availability of bacterial nutrients in the burn milieu, destruction of the vascular supply to the burned skin, and systemic disturbances lead to immunosuppression combined together to make burns particularly susceptible to infection. In the 20th century the introduction of antibiotic and antifungal drugs, the use of topical antimicrobials that could be applied to burns, and widespread adoption of early excision and grafting all helped to dramatically increase survival. However the relentless increase in microbial resistance to antibiotics and other antimicrobials has led to a renewed search for alternative approaches to prevent and combat burn infections. This review will cover patented strategies that have been issued or filed with regard to new topical agents, preparations, and methods of combating burn infections. Animal models that are used in preclinical studies are discussed. Various silver preparations (nanocrystalline and slow release) are the mainstay of many approaches but antimicrobial peptides, topical photodynamic therapy, chitosan preparations, new iodine delivery formulations, phage therapy and natural products such as honey and essential oils have all been tested. This active area of research will continue to provide new topical antimicrobials for burns that will battle against growing multidrug resistance.