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Non-adhering dressings are commonly used during granulation, tissue formation, and re-epithelialization. Elucidating cytotoxic effects and influence on proliferation/migration capacity of cells like fibroblasts is of interest. Dressings' effects were investigated by comprehensive in vitro approach: (1) MTT assay measuring cell viability after direct contact, (2) ATP assay determining effects on cell proliferation, and (3) scratch wound assay featuring an in vitro wound healing model. One cotton-based dressing with vaseline (vas) was included in the study and four polyester dressings containing vas and technology-lipido-colloid matrix (TLC), carboxymethylcellulose (CMC), hydrocolloid (HC), or glycerin (gly) as additives. A polyamide dressing with vas + CMC and three silicone-based dressings (AT, CC, M) were tested. Polyester + vas + CMC did not negatively affect cell viability or proliferation but it was found that fibroblast layers appeared more irregular with decreased F-actin network structure and tubulin density possibly leading to hampered scratch closure. Silicone AT, polyester + gly and polyamide + vas + CMC caused distinct cell damage. The latter two further reduced cell viability, proliferation and scratch healing. From the overall results, it can be concluded that cotton + vas, polyester + TLC, polyester + vas + HC and the silicone dressings CC and M have the potential to prevent damage of newly formed tissue during dressing changes and positively influence wound healing.

Superabsorbent polymer (SAP)-containing wound dressings present a valuable and unique category of wound management products. An in vitro approach was used to assess the effects of a new SAP dressing in treatment of non-healing wounds. It was shown that the SAP dressing possesses a significant binding capacity for MMP-2 and MMP-9 in vitro (P\0.001). The inclusion of the bound proteases was so strong that no MMP-2 and only marginal amounts of MMP-9 were released from the dressing samples in a subsequent elution step. In addition, the SAP dressing was able to take up collagenase and reduce its activity in vitro. However, collagenase was not completely inactivated upon binding and enzyme-mediated substrate turnover could be observed at the dressings. In conclusion, in vitro data confirm the positive effect of the SAP wound dressing observed in vivo. The findings suggest that it should be specifically useful for highly exuding wounds with an elevated proteolytic activity that needs to be reduced to support healing.

In the treatment of chronic wounds, it is necessary to establish a physiological wound milieu to improve healing. Application of collagen as wound dressing has been described as beneficial as it possesses the ability to reduce elevated levels of proteases, cytokines, and free radicals. Consequently, a wide range of wound dressings based on collagen have been developed. Native collagen is susceptible to alterations because of influences during the production process; to minimize effects on the molecule itself collagen wound dressings are usually aseptically produced. Common sterilization methods (autoclaving, irradiation, and ethylene oxide (EtO) treatment) can induce changes in the protein chemistry and physical properties, potentially affecting the absorption rate, mechanical strength, or performance. In this study, we have evaluated the influence of gamma- and beta-irradiation as well as EtO sterilization on the binding capacity of collagen type I for selected proteases and cytokines associated with nonhealing wounds. Although a pronounced effect on the physical properties of the collagen was found, there was no significant loss in the binding affinity for polymorphonuclear elastase, matrix metalloproteinase-2, and interleukin-1beta, or in the antioxidant capacity.

Background: Wound infection plays an important role in compromised wound healing. A high bioburden impairs healing and leads to formation of a chronic wound. Distinctly higher pH values were observed in chronic wounds compared to acute wounds. However, there is only limited knowledge of pH dependency on the antibacterial efficacy of common antimicrobial substances. Methods: This study investigated the pH influence on the antimicrobial efficacy of povidone (PVP)-iodine, silver nitrate, chlorhexidine, octenidine and polihexanide against Staphylococcus aureus and Pseudomonas aeruginosa using the agar diffusion test and microplate laser nephelometry. Results: The bactericidal activity of chlorhexidine and octenidine was mainly pH-independent in a pH range of 5.0-9.0. In contrast, polihexanide showed a significant efficacy increase at a higher pH. It was also found that the influence of the pH on antiseptics differs among species of bacteria. For instance, S. aureus exhibited an increasing sensitivity against silver nitrate with rising pH whereas the effect on P. aeruginosa was found to be distinctly decreased. The antimicrobial effect of PVP-iodine was strongly diminished with rising pH. Conclusions: The shift towards higher pH values in chronic wounds compared to acute wounds makes it imperative to know whether the antimicrobial efficacy of applied antimicrobial substances is altered by different pH levels. The results suggest that application of polihexanide might be advantageous for the management of wound infections, as both S. aureus and P. aeruginosa exhibited an increased susceptibility with rising pH. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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-α, 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. [ABSTRACT FROM AUTHOR]

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It is a general goal to improve wound healing, especially of chronic wounds. As light therapy has gained increasing attention, the positive influence on healing progression of water-filtered infrared A (wIRA), a special form of thermal radiation, has been investigated and compared to the detrimental effects of UV-B irradiation on wound closure in vitro. Models of keratinocyte and fibroblast scratches help to elucidate effects on epithelial and dermal healing. This study further used the simulation of non-optimal settings such as S. aureus infection, chronic inflammation, and anti-inflammatory conditions to determine how these affect scratch wound progression and whether wIRA treatment can improve healing. Gene expression analysis for cytokines (IL1A, IL6, CXCL8), growth (TGFB1, PDGFC) and transcription factors (NFKB1, TP53), heat shock proteins (HSP90AA1, HSPA1A, HSPD1), keratinocyte desmogleins (DSG1, DSG3), and fibroblast collagen (COL1A1, COL3A1) was performed. Keratinocyte and fibroblast wound healing under non-optimal conditions was found to be distinctly reduced in vitro. wIRA treatment could counteract the inflammatory response in infected keratinocytes as well as under chronic inflammatory conditions by decreasing pro-inflammatory cytokine gene expression and improve wound healing. In contrast, in the anti-inflammatory setting, wIRA radiation could re-initiate the acute inflammatory response necessary after injury to stimulate the regenerative processes and advance scratch closure. [ABSTRACT FROM AUTHOR]

Abstract: Exudates from non-healing wounds contain elevated levels of proteolytic enzymes, like elastase from polymorphonuclear granulocytes (PMN elastase), reactive oxygen species (ROS) and reactive nitrogen species (RNS). The overproduction of proteolytic enzymes leads to reduced concentrations of growth factors and proteinase inhibitors, resulting in an imbalance between degradation and remodelling processes. Thus, the reduction of protein-degrading enzymes and scavenging of ROS and RNS seem to be suitable ways to support the healing process of chronic stagnating wounds. The aim of this study was to test selected wound dressings from different biomaterials (collagen, oxidized regenerated cellulose (ORC) and ORC/collagen mixture), regarding their antioxidative potential in vitro and their influence on the concentration and activity of PMN elastase in chronic wound fluid. Antioxidant capacity of the investigated wound dressing was determined by a pholasin-based chemiluminescent assay. PMN elastase concentration was determined by means of ELISA. Enzyme activities could be measured by a fluorescence assay. As the presented data demonstrates, all tested materials showed antioxidant capacity. In addition, the investigated materials were able to reduce the concentration and activity of PMN elastase. Beside other aspects, such as biocompatibility, biodegradability, fluid absorption and clinical effects (e.g. angiogenesis and microcirculation), the understanding of these properties may help to support the further refinement of wound dressings for improved wound healing. [Copyright &y& Elsevier]