Application of weft-knitted spacer fabrics as absorbent dressings for exuding wounds

Abstract

Exuding period is a crucial but hard to manage period of a deep injured wound or burn. An ideal dressing for exuding wound requires quick and large absorbency, good thermal property, moisture management, air permeability and mechanical property. Fast wicking property and high absorbency help dressing to absorb all exudate immediately and avoid maceration of surrounding skin. This reduces the change frequency of wound dressing and the possibility to disturb the wound. The moisture should be managed in a certain range to keep wound physiologically moist, neither dry nor covered in fluid. In addition, dressing should be oxygen permeable to accelerate wound healing by promoting fibroblast proliferation and collagen synthesis. High heat keeping rate is required for maintaining the wound in a normal body temperature, which allows optimal cellular function. Furthermore, when applying on a wound, dressing should adapt to the body shape of the wound site. Currently commercial dressings for heavily exuding wounds still have some drawbacks, such as poor integrity, slow wicking property, poor air permeability, a need of secondary dressing and very high price. Spacer fabrics can well overcome these drawbacks and maximize their performance as dressing material. In this study, spacer-fabric-based dressing was firstly designed according to the requirements of exuding wound care. Three layers were included in the designed dressing. The wound contact layer should be a hydrophobic with quick moisture transmission rate, and the outer layer should be waterproof to protect the wound. Therefore, its two surfaces were produced with elastic synthetic yarns, and the spacer layer were knitted with absorbent yarns. Twelve different spacer fabrics were produced and their properties were assessed. Considering their good air permeability and appropriate absorbency and WVTR, spacer fabric knitted with cotton spacer yarn and with 4 needle connecting distance was selected as the basic material of the designed dressing. Then, the selected spacer fabric was processed with antibacterial treatment. A silver-containing spacer fabric was manufactured and analyzed. The silver distributions were compared between the spacer fabric and 4-layered cotton fabric. The results show that spacer fabric could keep the silver ions in the middle layer, the bacteria would be killed in the middle layer of dressing. The way to absorb wound exudates and kill bacteria within the dressings reduces silver concentration on the wound bed, and therefore this could be an efficient way to lower the potential of silver entering human body, and prevent the silver toxicity and wound-healing delay. As wound dressing should keep contaminated fluid and harmful substance away from the wound, water resistant treatments were carried out on spacer fabric surface. The aims of these methods were not only to make the spacer fabric water resistant but also to keep the good air permeability of spacer fabric. In this regard, three kinds of air permeable water resistant treatments were applied including treatment with electrospun nanofibrous polyurethane or polystyrene membrane, treatment with fluorocarbons agent NUVA N2114 and treatment with TiO2 nanosol. The treated spacer fabrics were evaluated by the water contact angle test and air permeability test. The spacer-fabric-based dressings were compared with three types of commercial dressings to evaluate their performance while using as absorbent dressings for exuding wounds. Different performance indicators including the wettability, absorbency, moisture transmission, air permeability, extensibility and water contact angle tests were tested. As a result, the spacer-fabric-based dressings could absorb large amount of fluid in a short period, and they were permeable for air and moist vapor while they were tended to keep a moist environment with low evaporation after absorbing. The biocompatibility and wound healing property of spacer-fabric-based wound dressing were evaluated by in vitro cytotoxicity study, animal intracutaneous reactivity study and in vivo wound healing study. The spacer-fabric-based dressing was considered no cytotoxicity potential on L929 mouse fibroblast cells. Also, the animals did not show any grade of erythema or edema after intradermal injection of the dressing extracts. In addition, the in vivo wound healing test showed that spacer-fabric-based dressing accelerated full thickness wound healing when comparing with cotton gauze. Spacer-fabric-based dressing can be a promising wound care product to facilitate wound healing.