Autocatalytically hydroxyl-producing composite wound dressing for bacteria-infected wound healing.

The creation of wound dressings with low drug resistance and broad-spectrum antibacterial capability is a key topic of scientific interest. To achieve this, a bactericidal wound dressing with the capacity to autocatalytically produce hydroxyl radicals (OH) was developed. The wound dressing was an electrospun PCL/gelatin/glucose composite fiber mesh (PGD) with functional iron-containing metal-organic framework (Fe-MOF) nanozymes. These functional nanozymes (G@Fe) were formed by coupling glucose oxidase (GOx) and Fe-MOF through amide bonds. These nanozymes enabled the conversion of glucose released from the PGD composite mesh into hydroxyl radicals via an autocatalytic cascade reaction to destroy bacteria. The antibacterial efficiency of wound dressings and their stimulation of tissue regeneration were assessed using a MRSA-infected skin wound infection model on the back of SD mice. The G@Fe/PGD wound dressing exhibited improved wound healing capacity and had comparable biosafety to commercial silver-containing dressings, suggesting a potential replacement in the future.

In vivo observations of biofilm adhering to a dialkylcarbamoyl chloride-coated mesh dressing when applied to diabetes-related foot ulcers: A proof of concept study.

In this proof-of-concept study of twenty participants, we sought to determine if a DACC (Dialkylcarbamoyl chloride)-coated mesh dressing demonstrates an ability to adhere biofilm when placed on Diabetes Related Foot Ulcers (DRFUs) with chronic infection. The study also sought to determine if removal of the DACC-coated mesh dressings contributes to reducing the total number of bacteria in DRFUs, by exploring the total microbial loads, microbial community composition, and diversity. Standard of care was provided in addition to the application of DACC or DACC hydrogel every three days for a total of two weeks. Wound swabs, tissue curettage, and soiled dressings were collected pre and post-treatment. Tissue specimens obtained pre-treatment were analysed with scanning electron microscopy (SEM) and peptide nucleic acid fluorescent in situ hybridisation (PNA-FISH) with confocal laser scanning microscopy and confirmed the presence of biofilm in all DRFUs. SEM confirmed the presence of biofilms readily adhered to soiled DACC-coated mesh dressings pre- and post-treatment in all participants. Real-time quantitative polymerase chain reaction (qPCR) demonstrated the mean total microbial load of DRFUs in 20 participants did not change after two weeks of therapy (pre-treatment = 4.31 Log10 16 S copies (±0.8) versus end of treatment = 4.32 Log10 16 S copies (±0.9), P = .96, 95% CI -0.56 to 0.5). 16 S sequencing has shown the microbial composition of DACC dressings and wound swabs pre- and post-treatment remained similar (DACC; R = -.047, P = .98, Swab; R = -.04, P = .86), indicating the microbial communities originate from the ulcer. Biofilms adhere to DACC-coated mesh dressings; however, this may not reduce the total microbial load present within DRFU tissue. Wound dressings for use in hard-to-heal wounds should be used as an adjunct to a good standard of care which includes debridement and wound bed preparation.

Significant and rapid reduction of free endotoxin using a dialkylcarbamoyl chloride-coated wound dressing.

OBJECTIVE: Endotoxin causes inflammation and can impair wound healing. Conventional methods that reduce bioburden in wounds by killing microorganisms using antibiotics, topical antimicrobials or antimicrobial dressings may induce endotoxin release from Gram-negative bacteria. Another approach is to reduce bioburden by adsorbing microorganisms, without killing them, using dialkylcarbamoyl chloride (DACC)-coated wound dressings. This study evaluated the endotoxin-binding ability of a DACC-coated wound dressing (Sorbact Compress, Abigo Medical AB, Sweden) in vitro, including its effect on the level of natural endotoxin released from Gram-negative bacteria. METHOD: Different concentrations of purified Pseudomonas aeruginosa endotoxin and a DACC-coated dressing were incubated at 37°C for various durations. After incubation, the dressing was removed and endotoxin concentration in the solution was quantified using a Limulus amebocyte lysate (LAL) assay. The DACC-coated dressing was also incubated with Pseudomonas aeruginosa cells for one hour at 37°C. After incubation, the dressing and bacterial cells were removed and shed endotoxin remaining in the solution was quantified. RESULTS: Overnight incubation of the DACC-coated wound dressing with various concentrations of purified Pseudomonas aeruginosa endotoxin (96-11000 EU/ml) consistently and significantly reduced levels of free endotoxin by 93-99% (p<0.0001). A significant endotoxin reduction of 39% (p<0.001) was observed after five minutes. The DACC-coated dressing incubated with clinically relevant Pseudomonas aeruginosa cells also reduced shed endotoxin by >99.95% (p<0.0001). CONCLUSION: In this study, we showed that a DACC-coated wound dressing efficiently and rapidly binds both purified and shed endotoxin from Pseudomonas aeruginosa in vitro. This ability to remove both endotoxin and bacterial cells could promote the wound healing process.

Antimicrobial effects of bacterial binding to a dialkylcarbamoyl chloride-coated wound dressing: an in vitro study.

OBJECTIVE: Wound dressings that inactivate or sequestrate microorganisms, such as those with a hydrophobic, bacteria-binding dialkylcarbamoyl chloride (DACC) surface, can reduce the risk of clinical infections. This 'passive' bioburden control, avoiding bacterial cell wall disruption with associated release of bacterial endotoxins aggravating inflammation, is advantageous in hard-to-heal wounds. Hence, the full scope of DACC dressings, including the potential impact of higher inoculum densities, increased protein load and different pH on antibacterial activity, needs to be evaluated. METHOD: The Japanese Industrial Standard (JIS) L 1902 challenge test was used to evaluate the antimicrobial activity of the DACC-coated dressing against several World Health Organization (WHO)-prioritised wound pathogens (e.g., meticillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, microorganisms with extended-spectrum beta-lactamases and Acinetobacter baumannii), the effect of repeated bacterial challenge in an adverse wound environment, and antimicrobial performance at wound-related pH. RESULTS: High antibacterial activity of the DACC-coated dressing against the WHO-prioritised bacteria strains by its irreversible binding and inhibition of growth of bound bacteria was confirmed using JIS L 1902. At increased inoculation densities, compared to standard conditions, the DACC-coated dressing still achieved strong-to-significant antibacterial effects. Augmenting the media protein content also affected antibacterial performance; a 0.5-1 log reduction in antibacterial activity was observed upon addition of 10% fetal calf serum. The pH did not influence antibacterial performance. The DACC-coated dressing also sustained antibacterial activity over subsequent reinfection steps. CONCLUSION: It can be assumed that the DACC-coated dressing exerts beneficial effects in controlling the wound bioburden, reducing the overall demand placed on antibiotics, without using antimicrobial substances.

Bud-Poplar-Extract-Embedded Chitosan Films as Multifunctional Wound Healing Dressing.

Wounds represent a major global health challenge. Acute and chronic wounds are sensitive to bacterial infection. The wound environment facilitates the development of microbial biofilms, delays healing, and promotes chronic inflammation processes. The aim of the present work is the development of chitosan films embedded with bud poplar extract (BPE) to be used as wound dressing for avoiding biofilm formation and healing delay. Chitosan is a polymer with antimicrobial and hydrating properties used in wound dressing, while BPE has antibacterial, antioxidative, and anti-inflammatory properties. Chitosan-BPE films showed good antimicrobial and antibiofilm properties against Gram-positive bacteria and the yeast Candida albicans. BPE extract induced an immunomodulatory effect on human macrophages, increasing CD36 expression and TGFß production during M1/M2 polarization, as observed by means of cytofluorimetric analysis and ELISA assay. Significant antioxidant activity was revealed in a cell-free test and in a human neutrophil assay. Moreover, the chitosan-BPE films induced a good regenerative effect in human fibroblasts by in vitro cell migration assay. Our results suggest that chitosan-BPE films could be considered a valid plant-based antimicrobial material for advanced dressings focused on the acceleration of wound repair.

Amplicon-based skin microbiome profiles collected by tape stripping with different adhesive film dressings: a comparative study.

BACKGROUND: Medical film dressings have been used to obtain skin microbiota for skin microbiome studies, although their adhesive force may be so strong that the skin could be injured when applied to those who have fragile skin, such as older people. Several products with less adhesive force are available, although their applicability for skin microbiome studies remains unknown. This study aimed to test whether the dressings with less adhesive force could be used for amplicon-based skin microbiome studies. A set of three different film dressings, with acrylic, urethane, or silicone adhesive, was applied to the back skin of nine healthy young participants. The copy number of the 16S ribosomal RNA (rRNA) gene, microbial compositions, and alpha and beta diversity indices were analyzed by amplicon analysis of the 16S rRNA gene using next-generation sequencing and were compared among the three film dressings. RESULTS: The dressing with acrylic adhesive yielded the highest copy number of 16S rRNA genes, followed by that with urethane adhesive. The silicone-adhesive dressing yielded a significantly lower copy number of the 16S rRNA gene. The microbial composition of skin microbiota was similar among the three film dressings, although significant differences in the relative abundance of Pseudomonas species and alpha diversity indices were found in the silicone-adhesive dressing. The Bray-Curtis dissimilarity was significantly higher between the acrylic- and silicone-adhesive dressings than between the acrylic- and urethane-adhesive dressings. No adverse effects related to tape stripping were observed for any of the film dressings. CONCLUSION: We recommend dressings with acrylic or urethane adhesive for amplicon-based skin microbiome studies. An acrylic adhesive has an advantage in the yield of skin microbiota, and a urethane adhesive should be chosen when applied to fragile skin. The adhesive force of the dressing with silicone adhesive was too weak to be used for collecting skin microbiota.

In Vitro Efficacy of Bacterial Cellulose Dressings Chemisorbed with Antiseptics against Biofilm Formed by Pathogens Isolated from Chronic Wounds.

Local administration of antiseptics is required to prevent and fight against biofilm-based infections of chronic wounds. One of the methods used for delivering antiseptics to infected wounds is the application of dressings chemisorbed with antimicrobials. Dressings made of bacterial cellulose (BC) display several features, making them suitable for such a purpose. This work aimed to compare the activity of commonly used antiseptic molecules: octenidine, polyhexanide, povidone-iodine, chlorhexidine, ethacridine lactate, and hypochlorous solutions and to evaluate their usefulness as active substances of BC dressings against 48 bacterial strains (8 species) and 6 yeast strains (1 species). A silver dressing was applied as a control material of proven antimicrobial activity. The methodology applied included the assessment of minimal inhibitory concentrations (MIC) and minimal biofilm eradication concentration (MBEC), the modified disc-diffusion method, and the modified antibiofilm dressing activity measurement (A.D.A.M.) method. While in 96-well plate-based methods (MIC and MBEC assessment), the highest antimicrobial activity was recorded for chlorhexidine, in the modified disc-diffusion method and in the modified A.D.A.M test, povidone-iodine performed the best. In an in vitro setting simulating chronic wound conditions, BC dressings chemisorbed with polyhexanide, octenidine, or povidone-iodine displayed a similar or even higher antibiofilm activity than the control dressing containing silver molecules. If translated into clinical conditions, the obtained results suggest high applicability of BC dressings chemisorbed with antiseptics to eradicate biofilm from chronic wounds.

Polymeric Microfiltration Membranes Modification by Supercritical Solvent Impregnation-Potential Application in Open Surgical Wound Ventilation.

This study investigated supercritical solvent impregnation of polyamide microfiltration membranes with carvacrol and the potential application of the modified membranes in ventilation of open surgical wounds. The impregnation process was conducted in batch mode at a temperature of 40 °C under pressures of 10, 15, and 20 MPa for contact times from 1 to 6 h. FTIR was applied to confirm the presence of carvacrol on the membrane surface. In the next step, the impact of the modification on the membrane structure was studied using scanning electron and ion beam microscopy and cross-filtration tests. Further, the release of carvacrol in carbon dioxide was determined, and finally, an open thoracic cavity model was applied to evaluate the efficiency of carvacrol-loaded membranes in contamination prevention. Carvacrol loadings of up to 43 wt.% were obtained under the selected operating conditions. The swelling effect was detectable. However, its impact on membrane functionality was minor. An average of 18.3 µg of carvacrol was released from membranes per liter of carbon dioxide for the flow of interest. Membranes with 30-34 wt.% carvacrol were efficient in the open thoracic cavity model applied, reducing the contamination levels by 27% compared to insufflation with standard membranes.

Long-Term Antibacterial Film Nanocomposite Incorporated with Patchouli Essential Oil Prepared by Supercritical CO2 Cyclic Impregnation for Wound Dressing.

Biocompatible skin wound dressing materials with long-term therapeutic windows and anti-infection properties have attracted great attention all over the world. The cooperation between essential oil and non-toxic or bio-based polymers was a promising strategy. However, the inherent volatility and chemical instability of most ingredients in essential oils make the sustained pharmacological activity of essential oil-based biomaterials a challenge. In this study, a kind of film nanocomposite loaded with patchouli essential oil (PEO-FNC) was fabricated. PEO-loaded mesoporous silica nanoparticles (PEO-MSNs) with drug load higher than 40 wt% were firstly prepared using supercritical CO2 cyclic impregnation (SCCI), and then combined with the film matrix consisting of polyvinyl alcohol and chitosan. The morphology of PEO-MSNs and PEO-FNC was observed by transmission and scanning electron microscope. The mechanical properties, including hygroscopicity, tensile strength and elongation at break (%), were tested. The release behavior of PEO from the film nanocomposite showed that PEO could keep releasing for more than five days. PEO-FNC exhibited good long-term (>48 h) antibacterial effect on Staphylococcus aureus and non-toxicity on mouse fibroblast (L929 cells), making it a promising wound dressing material.

Biodegradable collagen from Scomberomorus lineolatus skin for wound healing dressings and its application on antibiofilm properties.

The major resolution of the study was to develop a dynamic form of natural biopolymer material to improve the wound healing by inhibition of biofilm formation on the surface. The extraction of collagen was effectively prepared from Scomberomorus lineolatus fish skin. Lyophilized collagen sheet was liquefied in 0.5M acetic acid to form acidic solubilized collagen (ASC) for further analysis. Physicochemical characterization of ASC was performed by various techniques using a standard protocol. The yield of ASC form S.lineolatus is higher (21.5%) than the previous reported studies. The effect of collagen solubility is gradually decreases with increasing concentration of NaCl and collagen is mostly soluble in acidic pH conditions. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of ASC contains α chain composition of α1 and α2 subunits and was characterized as type I collagen. Ultraviolet absorption was regulated as the appropriate wavelength to optimize the collagen. Fourier-transform infrared spectroscopy and X-ray diffraction confirmed that the isolated collagen is a triple-helical structure. The biofilm formation of Pseudomonas aeruginosa was significantly reduced by collagen incorporated with isolated 3,5,7-trihydroxyflavone (collagen-TF) sheet up to 70%. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay executed on fibroblast cell lines (L929) shows that the collagen-TF sheet was 100% compatible to enrich the cell adhesion and proliferation. The current study was the first report to extract, purify, and characterize ASC from S. lineolatus fish skin and characterize as type I collagen. Based on the result, we design the natural biodegradable collagen loaded with TF compound (collagen-TF) for antibiofilm properties. Compared with different sources of polymer, fish skin collagen is more effective and can be used as a biopolymer sheet for wound healing, food, drug delivery, tissue engineering, and pharmaceutical application.

Estimating Bacterial Concentrations in Fibrous Substrates Through a Combination of Scanning Electron Microscopy and ImageJ.

Conventional signal-based microanalytical techniques for estimating bacterial concentrations are often susceptible to false signals. A visual quantification, therefore, may compliment such techniques by providing additional information and support better management decisions in the event of outbreaks. Herein, we explore a method that combines electron microscopy (EM) and image-analysis techniques and allows both visualization and quantification of pathogenic bacteria adherent even to complex nonuniform substrates. Both the estimation and imaging parameters were optimized to reduce the estimation error ( E, %) to close to ±5%. The method was validated against conventional microbiological techniques such as the use of optical density, flow cytometry, and quantitative real-time PCR (qPCR). It could easily be tailored to estimate different species of pathogens, such as Escherichia coli O157, Listeria innocua, Staphylococcus aureus, Enterococcus faecalis, and Bacillus anthracis, on samples similar to those in real-time contamination scenarios. The present method is sensitive enough to detect ∼100 bacterial CFU/mL but has the potential to estimate even lower concentrations with increased imaging and computation times. Overall, this imaging-based method may greatly complement any signal-based pathogen-detection technique, especially in negating false signals, and therefore may significantly contribute to the field of analytical microbiology and biochemistry.

Chlorhexidine-impregnated dressing for the prophylaxis of central venous catheter-related complications: a systematic review and meta-analysis.

BACKGROUND: Several randomized controlled trials (RCTs) evaluated the role of Chlorhexidine-impregnated dressing for prophylaxis of central venous catheter (CVC) related complications, but the results remained inconsistent, updated meta-analyses on this issue are warranted. METHODS: A meta-analysis on the RCTs comparing Chlorhexidine-impregnated dressing versus other dressing or no dressing for prophylaxis of central venous catheter-related complications was performed. A comprehensive search of major databases was undertaken up to 30 Dec 2018 to identify related studies. Pooled odd ratio (OR) and mean differences (MDs) with 95% confidence intervals (CI) were calculated using either a fixed-effects or random-effects model. Subgroup analysis was performed to identify the source of heterogeneity, and funnel plot and Egger test was used to identify the publication bias. RESULTS: A total of 12 RCTs with 6028 patients were included. The Chlorhexidine-impregnated dressings provided significant benefits in reducing the risk of catheter colonization (OR = 0.46, 95% CI: 0.36 to 0.58), decreasing the incidence of catheter-related bloodstream infection (CRBSI) (OR = 0.60, 95% CI: 0.42 to 0.85). Subgroup analysis indicated that the Chlorhexidine-impregnated dressings were conducive to reduce the risk of catheter colonization and CRBSI within the included RCTs with sample size more than 200, but the differences weren't observed for those with sample less than 200. No publication bias was observed in the Egger test for the risk of CRBSI. CONCLUSIONS: Chlorhexidine-impregnated dressing is beneficial to prevent CVC-related complications. Future studies are warranted to assess the role and cost-effectiveness of Chlorhexidine-impregnated dressings.

Stenotrophomonas maltophilia-A Case Series of a Rare Keratitis Affecting Patients With Bandage Contact Lens.

OBJECTIVES: Stenotrophomonas maltophilia is an opportunistic pathogen known to form biofilms on contact lens and case surfaces that may result in permanent visual loss in cases of microbial keratitis. Because of its multiple drug resistance and extremely low incidence, there is little consensus on treatment. We investigated the predisposing factors, management, and visual outcomes in a small case series of patients to better inform the management of this rarely reported keratitis. METHODS: Retrospective analysis of medical records was performed at a single tertiary referral center between 2011 and 2017. The case notes of each microbiology confirmed S. maltophilia keratitis were examined. RESULTS: Six cases were identified (four men) with a median age of 62 years (range 1 month-90 years) and pre-existing ocular surface disease in all cases. At presentation, four patients were using bandage contact lenses and three were on topical antibiotic and steroid medications. Initial antibiotic treatment was intensive topical 0.3% ofloxacin and 5% cefuroxime, which was modified based on corneal scrape culture and sensitivity and clinical findings. One patient chose not to complete the treatment course. The 5 remaining patients had complete resolution of ulceration over a mean of 2.9 months (SD 0.8 months). CONCLUSIONS: Contact lens in the context of ocular surface problems, prolonged topical antibiotic and steroid treatments may predispose to S. maltophilia, a rare cause of keratitis. We report successful treatment with case-specific combinations of topical antibiotics such as fluoroquinolone, cotrimoxazole, and/or cephalosporin agents, although visual outcomes remain poor due to corneal scar.

Mild Synthesis of Copper Nanoparticles with Enhanced Oxidative Stability and Their Application in Antibacterial Films.

Copper nanoparticles possess unique physical and chemical properties; however, their application is often restricted, owing to their tendency to oxidize. In this work, we prepared copper nanoparticles with enhanced oxidative stability via a simple and low-cost method, where a modified starch was used as an environmentally friendly reducing agent and biocompatible polyethylenimine was used as a stabilizer. The prepared copper nanoparticles could be stored in air for at least 6 months without any oxidation in a dried state. Interestingly, our synthesis could even be performed at room temperature with a longer reaction time. We used various characterization methods to study the reaction mechanism. The prepared copper nanoparticles were further uniformly doped into an agar film, and this composite showed excellent bacterial killing efficiency, owing to the antibacterial properties of the copper nanoparticles. Our composite film shows potential for various clinical applications, such as wound dressing materials.

Efficacy of a Surfactant-Based Wound Dressing in the Prevention of Biofilms.

OBJECTIVE: To assess the biofilm prevention action of two wound dressings, a concentrated surfactant gel preserved with antimicrobials and a concentrated surfactant gel with 1% silver sulfadiazine. METHODS: The microorganisms Staphylococcus aureus, methicillin-resistant S aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Enterococcus faecalis were used. Several biofilm models were used whereby the surfaces of each model were coated with either the concentrated surfactant gel preserved with antimicrobials or the concentrated surfactant gel with SSD before biofilm growth. MAIN RESULTS: Results showed the concentrated surfactant gel with SSD prevented biofilm growth in the modified minimum biofilm eradication concentration and Centers for Disease Control and Prevention biofilm models. The concentrated surfactant gel preserved with antimicrobials prevented microbial penetration for up to 48 hours, whereas the concentrated surfactant with SSD prevented microbial penetration for at least 72 hours. Using confocal laser scanning microscopy, researchers showed that a surface coated with the concentrated surfactant gel preserved with antimicrobials enhanced microbial sequestration of planktonic microorganisms. CONCLUSIONS: These results demonstrated that a concentrated surfactant gel preserved with antimicrobials can sequester and cause the immobilization of planktonic bacteria. Further, the concentrated surfactant gel with SSD can effectively kill planktonic and sessile microorganisms.

Microbial contamination of open-but-unused portions of wound dressings stored in home settings.

The purpose of this study was to investigate incidence rates and levels of microbial contamination in open-but-unused portions of wound dressings stored in home settings. Portions of wound dressings were collected at up to four home visits for 104 clients undertaking wound management within their home. A control sample and stored sample was collected on each home visit and sent for pathology testing to identify levels of microbial contamination. The stored open-but-unused wound dressings were managed according to a written protocol. Of the tested samples (n = 776), 6% of control samples and 7% of test samples had microbial contamination. From regression analysis, the stored samples were more likely to have microbial contamination than control samples, but results were not statistically significant. In comparing occasions of storage and handling across four home visits, after adjusting for sample group and dressing type, none of the home visit occasion regressions were statistically significant. In conclusion, storage of open-but-unused portions of wound dressings kept in home settings does not appear to increase the rate of microbial contamination compared to newly opened wound dressings.

Immobilization of bacteriophage in wound-dressing nanostructure.

Opportunistic bacteria that cause life-threatening infections are still a central problem associated with a healthcare setting. Bacteriophage capsid immobilization on nanostructured polymers maximizes its tail exposure and looks promising in applications toward skin-infections as alternative to antibiotics standardly used. The main goal of this work was to investigate the covalent immobilization of vB_Pae_Kakheti25 bacteriophage capsid on polycaprolactone (PCL) nanofibers (non-woven textile), as a potential effective antimicrobial, laundry resistant and non-toxic dressing for biomedical use. Surface analyses showed that the immobilization of vB_Pae_Kakheti25 bacteriophage capsid on PCL nanofibres oriented bacteriophage tails to interact with bacteria. Furthermore, antimicrobial assays showed a very effective 6 log bacterial reduction, which was equivalent to 99.9999%, after immediate and 2 hours of contact, even following 25 washing cycles (due to covalent bond). The activity of PCL-vB_Pae_Kakheti25 against P. aeruginosa was immediate and its reduction was complete.

N-Halamine Biocidal Materials with Superior Antimicrobial Efficacies for Wound Dressings.

This work demonstrated the successful application of N-halamine technology for wound dressings rendered antimicrobial by facile and inexpensive processes. Four N-halamine compounds, which possess different functional groups and chemistry, were synthesized. The N-halamine compounds, which contained oxidative chlorine, the source of antimicrobial activity, were impregnated into or coated onto standard non-antimicrobial wound dressings. N-halamine-employed wound dressings inactivated about 6 to 7 logs of Staphylococcus aureus and Pseudomonas aeruginosa bacteria in brief periods of contact time. Moreover, the N-halamine-modified wound dressings showed superior antimicrobial efficacies when compared to commercially available silver wound dressings. Zone of inhibition tests revealed that there was no significant leaching of the oxidative chlorine from the materials, and inactivation of bacteria occurred by direct contact. Shelf life stability tests showed that the dressings were stable to loss of oxidative chlorine when they were stored for 6 months in dark environmental conditions. They also remained stable under florescent lighting for up to 2 months of storage. They could be stored in opaque packaging to improve their shelf life stabilities. In vitro skin irritation testing was performed using a three-dimensional human reconstructed tissue model (EpiDerm™). No potential skin irritation was observed. In vitro cytocompatibility was also evaluated. These results indicate that N-halamine wound dressings potentially can be employed to prevent infections, while at the same time improving the healing process by eliminating undesired bacterial growth.

Germicide wound pad with active, in situ, electrolytically produced hypochlorous acid.

We describe a new wound dressing technology that can actively generate an inorganic germicide agent, in situ, within the wound pad. The technology provides real time control over the quantitative, spatial and temporal delivery of the germicide. The identity of the germicide is hypochlorous acid (HClO). The HClO is produced in a flexible wound pad, made of a composite of thin (micrometer scale) layers of various materials, with different electrochemical properties that enhance HClO production. Active control over the production of HClO is achieved by control of the pH and of the electric potential across the layers. The effectiveness of the Active HClO Pad (AHClOP) concept is demonstrated in a study on sterilization of E. coli in a deep wound contamination simulating gel. The performance of the AHClOP is compared with that of four commercial wound dressings. Results show that the AHClOP can sterilize throughout the gel, while the commercial dressings cannot.

Binding of two bacterial biofilms to dialkyl carbamoyl chloride (DACC)-coated dressings in vitro.

OBJECTIVE: To date only planktonic bacteria have been shown to bind irreversibly to dialkyl carbamoyl chloride (DACC)-coated Cutimed Sorbact dressings. Therefore, this study was designed to determine whether bacterial biofilm bound to the DACC-coated dressing in vitro. METHOD: Samples of DACC-coated dressings and uncoated control dressings (supplied by BSN medical Ltd, Hull) were placed in contact with plastic coverslips on which biofilms of either Pseudomonas aeruginosa or methicillin-resistant Staphylococcus aureus (MRSA) had been cultivated for 24 hours. Dressing samples were examined by scanning electron microscopy to detect the presence of biofilm. RESULTS: Pseudomonas aeruginosa biofilm bound avidly to both DACC-coated and uncoated dressing samples. MRSA bound more extensively to DACC-coated dressings than to uncoated samples. CONCLUSION: Biofilms of two different test bacteria bound to dressings in vitro with the DACC-coating on the dressings enhancing the binding of MRSA biofilm. DECLARATION OF INTEREST: This study was supported by BSN medical Ltd (Hull). The company had no influence on the experimental design or the interpretation of the results.