In vitro cytotoxity of silver: implication for clinical wound care

Biofilms and delayed healing - an in vitro evaluation of silver- and iodine-containing dressings and their effect on bacterial and human cells

This study investigated whether there are differences in the ability of wound dressings to modulate certain factors known to affect wound healing. A selection of antimicrobial dressings (AQUACEL® Ag Extra™ , AQUACEL® Ag+ Extra™ , IODOFLEX™ , ACTICOAT™ 7 and PROMOGRAN PRISMA™ matrix) were tested for their effect on both bacterial bioburden and human dermal fibroblasts. Some dressings underwent further evaluation for activity against Pseudomonas aeruginosa biofilms using a colony-drip flow reactor model. The ability of in vitro biofilms to produce proteases, and the effect of PROMOGRAN PRISMA matrix on such proteases, was also investigated. All antimicrobial dressings tested reduced vegetative bacterial load; however, only PROMOGRAN PRISMA matrix was able to significantly reduce biofilm populations (P = 0·01). Additionally, PROMOGRAN PRISMA matrix was the only dressing that did not inhibit dermal fibroblast growth. All other dressings were detrimental to cell viability. In vitro biofilms of Pseudomonas aeruginosa were demonstrated as being capable of releasing bacterial proteases into their surroundings, and incubation with PROMOGRAN PRISMA matrix led to a 77% reduction in activity of such proteases (P = 0·002). The unique ability of PROMOGRAN PRISMA matrix to reduce in vitro vegetative bacteria, biofilm bacteria and bacterial proteases while still allowing dermal fibroblast proliferation may help rebalance the wound environment and reduce the occurrence of infection.

Sub-cytotoxic concentrations of ionic silver promote the proliferation of human keratinocytes by inducing the production of reactive oxygen species

Silver-containing preparations are widely used in the management of skin wounds, but the effects of silver ions on skin wound healing remain poorly understood. This study investigated the effects of silver ions (Ag⁺) on the proliferation of human skin keratinocytes (HaCaT) and the production of intracellular reactive oxygen species (ROS). After treating HaCaT cells with Ag⁺ and/or the active oxygen scavenger N-acetyl cysteine (NAC), cell proliferation and intracellular ROS generation were assessed using CCK-8 reagent and DCFH-DA fluorescent probe, respectively. In addition, 5-bromo-2-deoxyUridine (BrdU) incorporation assays, cell cycle flow cytometry, and proliferating cell nuclear antigen (PCNA) immunocytochemistry were conducted to further evaluate the effects of sub-cytotoxic Ag⁺ concentrations on HaCaT cells. The proliferation of HaCaT cells was promoted in the presence of 10^-6 and 10^-5 mol/L Ag⁺ at 24, 48, and 72 h. Intracellular ROS generation also significantly increased for 5-60 min after exposure to Ag⁺. The number of BrdU-positive cells and the presence of PCNA in HaCaT cells increased 48 h after the addition of 10^-6 and 10^-5 mol/L Ag⁺, with 10^-5 mol/L Ag⁺ markedly increasing the cell proliferation index. These effects of sub-cytotoxic Ag⁺ concentrations were repressed by 5 mmol/L NAC. Our results suggest that sub-cytotoxic Ag⁺ concentrations promote the proliferation of human keratinocytes and might be associated with a moderate increase in intracellular ROS levels. This study provides important experimental evidence for developing novel silver-based wound agents or dressings with few or no cytotoxicity.

Lateral flow test for visual detection of silver (I) based on cytosine-Ag(I)-cytosine interaction in C-rich oligonucleotides

The authors describe an oligonucleotide-based lateral flow test for visual detection of Ag(I). The assay is based on cytosine-Ag(I)-cytosine [C-Ag(I)-C] coordination chemistry to capture gold nanoparticle (AuNP) tags in the test zone. A thiolated C-rich oligonucleotide probe was immobilized on the AuNPs via gold-thiol chemistry, and a biotinylated C-rich oligonucleotide probe was immobilized on the test zone. The AuNPs labelled with C-rich oligonucleotides are captured by Ag(I) ions in the test zone through the C-Ag(I)-C coordination. The resulting accumulation of AuNPs produces a readily visible red band in the test zone. Under optimized conditions, the test is capable of visually detecting 1.0 ppb of Ag(I) which is 50 times lower than the maximum allowable concentration as defined by the US Environmental Protection Agency for drinking water. Hence, the test is inexpensive and highly sensitive. It was applied to the detection of Ag(I) in spiked samples of tap water and river water. In our perception, the test is a particularly valuable tool in limited resource settings.

Topical antimicrobial agents for pediatric burns

While topical antimicrobial agents are indicated for most if not all burn wounds, the choice of a topical agent must consider many factors such as the wound depth, anticipated time to healing, need for surgical intervention, and the known cytotoxicity of the agent. Especially relevant to the pediatric burn patient are the antimicrobial agent’s properties related to causing pain or irritation and the required frequency of application and dressings. This article will discuss the general principles surrounding the use of topical antimicrobials on burn wounds and will review the most common agents currently in use.

Application of Hyperosmotic Nanoemulsions in Wound Healing: Partial Thickness Injury Model in Swine

Objective: In this work, we introduce a novel hyperosmotic nanoemulsion (HNE) topical agent for use in wound healing. These topical emulsion complexes combine a lipophilic thymol nanoemulsion with a hyperosmotic saccharide matrix. This combination has been previously shown to possess synergistic antimicrobial activity against a host of common and drug-resistant pathogens in vitro. Approach: In this study, we present additional data to assess the safety and efficacy of these emulsions in a partial thickness injury model in swine. Ten wounds sized 2 × 3.5 cm were created in 18 pigs using an electrodermatome set at a depth of 0.76 mm. The wounds were subsequently contaminated with a cocktail of Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, and Candida albicans at 5 × 10⁷ total colony forming unit per wound. Treatments were subdivided in the control group and emulsion concentrations at 0.0%, 0.01%, 0.03%, and 0.063% thymol content. Longitudinal metrics for wound healing included rate of reepithelialization, wound bed color measurements, amount of wound exudate, wound swab culture data, and histological examination at 4, 7, and 14 days. The cosmetics of the healed wound were obtained at day 14 with three-dimensional photogrammetry. Results: Experimental results showed that HNE reduced the wound level bacteria count by ∼0.5-1 log versus controls after 24 h. The amount of pathogen reduction was weakly correlated to the concentration of the emulsion. In addition, all HNE groups maintained a moist wound environment and showed increased fibrin formation and improved hemostatic response. Innovation: No significant difference in the rate of reepithelialization or wound closure was found between treatment concentrations and control groups. HNE treatment did not demonstrate any adverse host tissue response. Conclusion: These results suggest HNE may be a candidate for reducing wound bacterial counts without compromising reepithelialization.

Silk Fibroin Biomaterial Shows Safe and Effective Wound Healing in Animal Models and a Randomized Controlled Clinical Trial

Due to its excellent biological and mechanical properties, silk fibroin has been intensively explored for tissue engineering and regenerative medicine applications. However, lack of translational evidence has hampered its clinical application for tissue repair. Here a silk fibroin film is developed and its translational potential is investigated for skin repair by performing comprehensive preclinical and clinical studies to fully evaluate its safety and effectiveness. The silk fibroin film fabricated using all green chemistry approaches demonstrates remarkable characteristics, including transmittance, fluid handling capacity, moisture vapor permeability, waterproofness, bacterial barrier properties, and biocompatibility. In vivo rabbit full-thickness skin defect study shows that the silk fibroin film effectively reduces the average wound healing time with better skin regeneration compared with the commercial wound dressings. Subsequent assessment in porcine model confirms its long-term safety and effectiveness for full-thickness skin defects. Finally, a randomized single-blind parallel controlled clinical trial with 71 patients shows that the silk fibroin film significantly reduces the time to wound healing and incidence of adverse events compared to commercial dressing. Therefore, the study provides systematic preclinical and clinical evidence that the silk fibroin film promotes wound healing thereby establishing a foundation towards its application for skin repair and regeneration in the clinic.

Cytotoxicity testing of burn wound dressings: first results

Topical antimicrobial therapy represents an essential part of burn wound care. In order to prevent and treat burn wound infection dressings with antimicrobial properties are applied directly on the wound surface. Not only the infection control but also promotion of healing is very important in burn wound management. It is well known, that a dressing in bactericidal concentration might also delay wound healing. This study was aimed to evaluate the potential toxic effect of topical antimicrobial agents on murine and human dermal cells. For toxicity testing the method by Vittekova et al. was used to evaluate potential toxic effects of 16 agents and 6 control samples on two in vitro cultured cell systems [3T3 cells and dermal fibroblasts] during the first 24 h. Following the 24 h cell culture with the tested agents the live cell counts were evaluated. According to results obtained on both cell systems, the tested samples were divided into three groups-nontoxic, semi-toxic and toxic. Nontoxic samples included Acetic acid 1%, Acticoat^®, Dermacyn^®, Framykoin^®, Silverlon^®, gauze, acellular human allodermis and acellular porcine xenodermis. Semi-toxic group included Algivon^®Plus, Aquacel^®Ag, Betadine^®, Nitrofurazone, Octenisept^®, Suprasorb^® A and a porcine dermal scaffold Xeno-Impl. Finally, the toxic group included Algivon^®, Dermazin^®, Ialugen^®Plus, Prontoderm^®, Suprasorb^® A Ag and 20% SDS. As the preliminary results of this study have shown, our findings may serve as a potential guide to selection of the most appropriate topical antimicrobial dressings for treatmet of burns. However before they can be translated into clinical practice recommendations, more research on antimicrobial dressings cytotoxicity testing will be necessary.

Collagen tethering of synthetic human antimicrobial peptides cathelicidin LL37 and its effects on antimicrobial activity and cytotoxicity

Wound infections, particularly of chronic wounds, pose a substantial challenge for designing antimicrobial dressings that are both effective against pathogens, and do not interfere with wound healing. Due to their broad-spectrum antimicrobial and immunomodulatory activities, naturally-occurring antimicrobial peptides (AMPs) are promising alternative treatments. However, their cytotoxicity at high concentrations and poor stability hinders their clinical use. To mitigate these undesirable properties, we investigated the effects of tethering human AMP cathelicidin LL37 to collagen, one of the main extracellular matrix proteins in wound sites, secreted by fibroblasts, and in commercially-available wound dressings. The active domain of human AMP cathelicidin, LL37, and two chimeric peptides containing LL37 fused to collagen binding domains (derived from collagenase - cCBD-LL37 or fibronectin - fCBD-LL37) were synthesized and adsorbed to PURACOL® type I collagen scaffolds. After 14days, 73%, 81% and 99% of LL37, cCBD-LL37 and fCBD-LL37, respectively, was retained on the scaffolds and demonstrated undiminished antimicrobial activity when challenged with both Gram-positive and Gram-negative bacterial strains. Loaded scaffolds were not cytotoxic to fibroblasts despite retaining peptides at concentrations 24 times higher than the reported cytotoxic concentrations in solution. These findings indicate that biopolymer-tethered AMPs may represent a viable alternative for preventing and treating wound infection while also supporting tissue repair.

STATEMENT OF SIGNIFICANCE

Over 6.5million people annually in the United States suffer chronic wounds; many will become infected with antibiotic-resistant bacteria. Treatments used to prevent and fight infection are toxic and may hinder wound healing. AMPs are broad-spectrum antimicrobials that also promote healing; however, their instability and toxicity are major challenges. To overcome treatment gaps, we functionalized collagen scaffolds with chimeric antimicrobial peptides (AMPs) with collagen binding domains to create antimicrobial and non-cytotoxic scaffolds that may promote healing. This is the first report of CBD-mediated delivery of AMPs onto collagen scaffolds that demonstrates no cytotoxicity toward fibroblasts. This study also suggests that retention of antimicrobial activity is CBD-dependent, which provides foundations for fundamental studies of CBD-AMP mechanisms and clinical explorations.

Beyond conventional antibiotics - New directions for combination products to combat biofilm

Medical device related infections are a significant and growing source of morbidity and mortality. Biofilm formation is a common feature of medical device infections that is not effectively prevented or treated by systemic antibiotics. Antimicrobial medical device combination products provide a pathway for local delivery of antimicrobial therapeutics with the ability to achieve high local concentrations while minimizing systemic side effects. In this review, we present considerations for the design of local antimicrobial delivery systems, which can be facilitated by modeling local pharmacokinetics in the context of the target device application. In addition to the need for local delivery, a critical barrier to progress in the field is the need to incorporate agents effective against biofilm. This article aims to review key properties of antimicrobial peptides that make them well suited to meet the demands of the next generation of antimicrobial medical devices, including broad spectrum activity, rapid and biocidal mechanisms of action, and efficacy against biofilm.

In Vitro Parallel Evaluation of Antibacterial Activity and Cytotoxicity of Commercially Available Silver-Containing Wound Dressings

PURPOSE

This study evaluated the in vitro antibacterial activity and cytotoxicity of various commercially available silver-containing dressings (Ag dressing).

METHODS

Biohesive Ag (hydrocolloid, silver sulfadiazine), Aquacel® Ag (nonwoven fabric, ionic silver [Ag]), Algisite™ Ag (nonwoven fabric, Ag), Mepilex® Ag (foam, silver sulfate), and PolyMem® Ag (foam, nanocrystalline silver) were tested for characteristics of Ag release, antibacterial activity, and cytotoxicity. The release of Ag was investigated in cell culture medium at immersion periods of 6, 24, and 48 hours. The antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa were accessed by a disc diffusion test. The cytotoxicity was evaluated using V79 cells, by an extraction method.

RESULTS

The cytotoxicity was not a monotonic function of the antibacterial activity among the Ag dressings and could not be simply explained by Ag-release properties. Biohesive Ag was regarded as a slow-release Ag dressing, showing the lowest cytotoxicity, while the antibacterial activity was classified as "strong" or "significant" against the two species of bacteria. Aquacel Ag and Algisite Ag showed higher antibacterial activity and cytotoxic effects, which were supported by the higher Ag release. Mepilex Ag showed the highest release of Ag, and the cytotoxicity was the highest among the Ag dressings. However, the antibacterial activity was classified as "significant" or "no activity" for P. aeruginosa and S. aureus, respectively. PolyMem Ag showed the lowest Ag release, and the antibacterial activity classified as "significant" or "no activity" for S. aureus and P. aeruginosa, respectively, whereas the cytotoxicity was similar to those of Aquacel Ag and Algisite Ag.

CONCLUSION

The efficacy and adverse effects of the Ag dressings revealed differences that should be considered by clinicians during wound management.

Fabrication and characterization of electrospun poly(e-caprolactone) fibrous membrane with antibacterial functionality

This research study is mainly targeted on fabrication and characterization of antibacterial poly(e-caprolactone) (PCL) based fibrous membrane containing silver chloride particles. Micro/nano fibres were produced by electrospinning and characterized with TGA, DSC, SEM and mechanical analysis. It was found that addition of silver particles slightly reduced onset of thermal degradation and increased crystallization temperature of neat PCL. Silver-loaded samples exhibited higher tensile stress and lower strain revealing that the particles behaved as reinforcing agent. Moreover, addition of silver chloride resulted in beaded surface texture and formation of finer fibres as opposed to the neat. Antibacterial properties were tested against Gram-negative and Gram-positive bacteria and remarkable biocidal functionalities were obtained with about six logs reduction of Staphylococcus aureus and Escherichia coli O157:H7.

Anti-inflammatory and burn injury wound healing properties of the shell of Haliotis diversicolor

Background

The shell of Haliotis diversicolor, or shijueming (SJM), is a type of traditional Chinese medicine. The SJM has appeared in historical records as early as the third and fourth centuries. Historical records have revealed that SJM had mainly been used to treat eye diseases. After the Qing Dynasty (1757), records had emerged, detailing the use of SJM for treating skin injuries, particularly for treating poorly managed ulcers or traumatic wounds. Furthermore, in our anti-inflammation-screening system, SJM significantly inhibited the expression of pro-inflammatory proteins. Previous studies have yet to adopt an animal model to verify the phenomenon and described in the historical records regarding the efficacy of SJM in promoting wound healing. Besides, the mechanism of wound healing effect of SJM is also not clear.

Methods

This study applied in vitro and in vivo models, tissue section analysis, and western blotting to evaluate the effect of SJM on wound healing. The RAW 264.7 cells were used in anti-inflammatory activity assay and phagocytic assay. Male Wistar rats were used to evaluate the effect of SJM on burn injury healing. A copper block (2 × 2 cm, 150 g) preheated to 165 °C in a dry bath was used to contact the skin area for 10 s, thus creating a full-thickness burn injury. The results were analyzed by hematoxylin and eosin staining, picrosirius red staining and Western blotting.

Results

The results revealed that in the in vitro model, the presence of SJM decreased the inducible nitric oxide synthase (iNOS) expression and enhanced the functions of macrophages. The results of the rat burn injury model revealed that SJM decreased neutrophil infiltration, promoted wound healing, thus increasing the collagen I content and promoting the expression of transforming growth factor-beta 1 (TGF-β1) protein. We speculate that the effect and mechanism of SJM on promoting wound healing is related to macrophage activation. In the inflammation phase, SJM alleviates inflammation by inhibiting iNOS expression and removing neutrophils through phagocytosis. Furthermore, SJM induces the secretion of TGF-β1, converting collagen during the tissue remodeling phase.

Conclusions

According to our review of relevant literature, this is the first study that applied an evidence-based method to verify that SJM alleviates inflammation, enhances phagocytosis, and triggers wound healing after burn injury. The study findings reveal that SJM provides a promising therapeutic option for treating burn injury.

Fabrication of transparent quaternized PVA/silver nanocomposite hydrogel and its evaluation as an antimicrobial patch for wound care systems

Grafting of quaternary nitrogen atoms into the backbone of polymer is an efficient way of developing new generation antimicrobial polymeric wound dressing. In this study, an elastic, non-adhesive and antimicrobial transparent hydrogel based dressing has been designed, which might be helpful for routine observation of wound area without removing the dressing material along with maintaining a sterile environment for a longer period of time. Green synthesized silver nanoparticles have been loaded into the quaternized PVA hydrogel matrix to improve its antimicrobial property. Silver nanoparticles loaded quaternized PVA hydrogel showed enhanced mechanical and swelling properties compared to native quaternized PVA hydrogel. Release kinetics evaluated by atomic absorption spectroscopy revealed that the release mechanism of silver nanoparticles from the hydrogel follows Fickian diffusion. Antimicrobial efficacy of the hydrogels was evaluated by disk diffusion test on Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli. After 96 h of release in phosphate buffer, the growth inhibition zone created by silver nanoparticless loaded quaternized PVA hydrogel is comparable to that created by ampicillin. These observations assert that the silver nanoparticles loaded quaternized PVA hydrogel acts as a reservoir of silver nanoparticles, which helps in maintaining a sterile environment for longer time duration by releasing Ag nanocrystallite in sustained manner.

Plasma-modified nitric oxide-releasing polymer films exhibit time-delayed 8-log reduction in growth of bacteria

Tygon(®) and other poly(vinyl chloride)-derived polymers are frequently used for tubing in blood transfusions, hemodialysis, and other extracorporeal circuit applications. These materials, however, tend to promote bacterial proliferation which contributes to the high risk of infection associated with device use. Antibacterial agents, such as nitric oxide donors, can be incorporated into these materials to eliminate bacteria before they can proliferate. The release of the antimicrobial agent from the device, however, is challenging to control and sustain on timescales relevant to blood transport procedures. Surface modification techniques can be employed to address challenges with controlled drug release. Here, surface modification using H2O (v) plasma is explored as a potential method to improve the biocompatibility of biomedical polymers, namely, to tune the nitric oxide-releasing capabilities from Tygon films. Film properties are evaluated pre- and post-treatment by contact angle goniometry, x-ray photoelectron spectroscopy, and optical profilometry. H2O (v) plasma treatment significantly enhances the wettability of the nitric-oxide releasing films, doubles film oxygen content, and maintains surface roughness. Using the kill rate method, the authors determine both treated and untreated films cause an 8 log reduction in the population of both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Notably, however, H2O (v) plasma treatment delays the kill rate of treated films by 24 h, yet antibacterial efficacy is not diminished. Results of nitric oxide release, measured via chemiluminescent detection, are also reported and correlated to the observed kill rate behavior. Overall, the observed delay in biocidal agent release caused by our treatment indicates that plasma surface modification is an important route toward achieving controlled drug release from polymeric biomedical devices.

Multi-biofunction of antimicrobial peptide-immobilized silk fibroin nanofiber membrane: Implications for wound healing

An antimicrobial peptide motif (Cys-KR12) originating from human cathelicidin peptide (LL37) was immobilized onto electrospun SF nanofiber membranes using EDC/NHS and thiol-maleimide click chemistry to confer the various bioactivities of LL37 onto the membrane for wound care purposes. Surface characterizations revealed that the immobilization density of Cys-KR12 on SF nanofibers could be precisely controlled with a high reaction yield. The Cys-KR12-immobilized SF nanofiber membrane exhibited antimicrobial activity against four pathogenic bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa) without biofilm formation on the membrane surface. It also facilitated the proliferation of keratinocytes and fibroblasts and promoted the differentiation of keratinocytes with enhanced cell-cell attachment. In addition, immobilized Cys-KR12 significantly suppressed the LPS-induced TNF-α expression of monocytes (Raw264.7) cultured on the membrane. These results suggest that a Cys-KR12-immobilized SF nanofiber membrane, which has multiple biological activities, would be a promising candidate as a wound dressing material.

STATEMENT OF SIGNIFICANCE

This research article reports various bioactivities of an antimicrobial peptide on electrospun silk fibroin nanofiber membrane. Recently, human cathelicidin peptide LL37 has been extensively explored as an alternative antibiotic material. It has not only a great antimicrobial activity but also a wide variety of bioactivities which can facilitate wound healing process. Especially, many studies on immobilization of LL37 or its analogues have shown the immobilization technique could improve performance of wound dressing materials or tissue culture matrices. Nevertheless, so far studies have only focused on the bactericidal effect of immobilized peptide on material surface. On the other hand, we tried to evaluate multi-biofunction of immobilized antimicrobial peptide Cys-KR12, which is the shortest peptide motif as an analogue of LL37. We fabricated silk fibroin nanofiber membrane as a model wound dressing by electrospinning and immobilized the antimicrobial peptide. As a result, we confirmed that the immobilized peptide can play multi-role in wound healing process, such as antimicrobial activity, facilitation of cell proliferation and keratinocyte differentiation, and inhibition of inflammatory cytokine expression. These findings have not been reported and can give an inspiration in wound-care application.

Traditional Therapies for Skin Wound Healing

Significance: The regeneration of healthy and functional skin remains a huge challenge due to its multilayer structure and the presence of different cell types within the extracellular matrix in an organized way. Despite recent advances in wound care products, traditional therapies based on natural origin compounds, such as plant extracts, honey, and larvae, are interesting alternatives. These therapies offer new possibilities for the treatment of skin diseases, enhancing the access to the healthcare, and allowing overcoming some limitations associated to the modern products and therapies, such as the high costs, the long manufacturing times, and the increase in the bacterial resistance. This article gives a general overview about the recent advances in traditional therapies for skin wound healing, focusing on the therapeutic activity, action mechanisms, and clinical trials of the most commonly used natural compounds. New insights in the combination of traditional products with modern treatments and future challenges in the field are also highlighted. Recent Advances: Natural compounds have been used in skin wound care for many years due to their therapeutic activities, including anti-inflammatory, antimicrobial, and cell-stimulating properties. The clinical efficacy of these compounds has been investigated through in vitro and in vivo trials using both animal models and humans. Besides the important progress regarding the development of novel extraction methods, purification procedures, quality control assessment, and treatment protocols, the exact mechanisms of action, side effects, and safety of these compounds need further research. Critical Issues: The repair of skin lesions is one of the most complex biological processes in humans, occurring throughout an orchestrated cascade of overlapping biochemical and cellular events. To stimulate the regeneration process and prevent the wound to fail the healing, traditional therapies and natural products have been used with promising results. Although these products are in general less expensive than the modern treatments, they can be sensitive to the geographic location and season, and exhibit batch-to-batch variation, which can lead to unexpected allergic reactions, side effects, and contradictory clinical results. Future Directions: The scientific evidence for the use of traditional therapies in wound healing indicates beneficial effects in the treatment of different lesions. However, specific challenges remain unsolved. To extend the efficacy and the usage of natural substances in wound care, multidisciplinary efforts are necessary to prove the safety of these products, investigate their side effects, and develop standard controlled trials. The development of good manufacturing practices and regulatory legislation also assume a pivotal role in order to improve the use of traditional therapies by the clinicians and to promote their integration into the national health system. Current trends move to the development of innovative wound care treatments, combining the use of traditional healing agents and modern products/practices, such as nanofibers containing silver nanoparticles, Aloe vera loaded into alginate hydrogels, propolis into dressing films, and hydrogel sheets containing honey.

Antimicrobial Wound Dressing Containing Silver Sulfadiazine With High Biocompatibility: In Vitro Study

Many patients all over the world suffer from acute wounds caused by traumas or burns. In most crucial cases, skin regeneration cannot be promoted spontaneously, and skin grafts are applied as the main treatment. However, this therapy has some drawbacks which motivate researchers to develop wound dressings. In this study, electrospun mats consisting of polycaprolactone (PCL) and polyvinyl alcohol (PVA) incorporated with silver sulfadiazine (SSD) are proposed to be used as antimicrobial wound dressings with the capability of cell seeding. Various amounts of SSD were loaded into PVA nanofibers, and the effects of SSD particles on the morphological characteristics of nanofibers, mechanical behaviors, and physical properties of the mats were studied for the first time. The cellular viability, antimicrobial properties of the scaffolds, and release behavior of silver were also examined. Finally, the best concentration of SSD was determined based on the quality of nanofibers, antibacterial features, and the ability of cellular attachment and proliferation. Fibronectin was also coated to enhance the biocompatibility of the selective scaffold. It was shown that the mats have appropriate mechanical properties with good handling ability in wet environment and also have a hydrophilic surface to adhere to the wound bed. Results indicate that SSD particles increase the fiber diameter and hydrophilic properties, while they weaken the mechanical characteristics of the mats. Furthermore, 5 wt% SSD/PVA was determined as the best concentration of SSD as it results in a desirable fiber quality for the mats with enough antimicrobial properties and acceptable cell proliferation on the surface. Coating fibronectin was also introduced as an effective method to increase the biocompatibility of the scaffolds incorporated with SSD particles.

Drug loaded composite oxidized pectin and gelatin networks for accelerated wound healing

Biocomposite interactive wound dressings have been designed and fabricated using oxidized pectin (OP), gelatin and nonwoven cotton fabric. Due to their inherent virtues of antimicrobial activity and cytocompatibility, these composite structures are capable of redirecting the healing cascade and influencing cell attachment and proliferation. A novel in situ reduction process has been followed to synthesize oxidized pectin-gelatin-nanosilver (OP-Gel-NS) flower like nanohydrocolloids. This encapsulation technology controls the diffusion and permeation of nanosilver into the surrounding biological tissues. Ciprofloxacin hydrochloride has also been incorporated into the OP-Gel matrix to produce OP-Gel-Cipro dressings. While OP-Gel-NS dressings exhibited 100% antimicrobial activity at extremely low loadings of 3.75μg/cm(2), OP-Gel-Cipro dressings were highly antimicrobial at 1% drug loading. While NIH3T3 mouse fibroblasts proliferated remarkably well when cultured with OP-Gel and OP-Gel-Cipro dressings, OP-Gel-NS hindered cell growth and Bactigras(®) induced complete lysis. Full thickness excisional wounds were created on C57BL/6J mice and the wound healing potential of the OP-Gel-NS dressings led to accelerated healing within 12days, while OP-Gel-Cipro dressings healed wounds at a rate similar to that of Bactigras(®). Histological examination revealed that OP-Gel-NS and OP-Gel-Cipro treatment led to organized collagen deposition, neovascularization and nuclei migration, unlike Bactigras(®). Therefore, the OP-Gel-NS and OP-Gel-Cipro biocomposite dressings exhibiting good hydrophilicity, sustained antimicrobial nature, promote cell growth and proliferation, and lead to rapid healing, can be considered viable candidates for effective management.

Clinical effectiveness, quality of life and cost-effectiveness of Flaminal® versus Flamazine® in the treatment of partial thickness burns: study protocol for a randomized controlled trial

Background

Partial thickness burns are painful, difficult to manage and can have a negative effect on quality of life through scarring, permanent disfigurement and loss of function. The aim of burn treatment in partial thickness burns is to save lives, stimulate wound healing by creating an optimumly moist wound environment, to have debriding and analgesic effects, protect the wound from infection and be convenient for the patient and caregivers. However, there is no consensus on the optimal treatment of partial thickness wounds. Flaminal® and Flamazine® are two standard treatment options that provide the above mentioned properties in burn treatment. Nevertheless, no randomized controlled study has yet compared these two common treatment modalities in partial thickness burns. Thus, the aim of this study is to evaluate the clinical effectiveness, quality of life and cost-effectiveness of Flaminal® versus Flamazine® in the treatment of partial thickness burns.

Methods/Design

In this two-arm open multi-center randomized controlled trial, 90 patients will be randomized between Flaminal® and Flamazine® and followed for 12 months. The study population will consist of competent or temporarily non-competent (because of sedation and/or intubation) patients, 18 years of age or older, with acute partial thickness burns and a total body surface area (TBSA) of less than 30 %. The main study outcome is time to complete re-epithelialization (greater than 95 %). Secondary outcome measures include need for grafting, wound colonization/infection, number of dressing changes, pain and anxiety, scar formation, health-related quality of life (HRQoL), and costs.

Discussion

This study will contribute to the optimal treatment of patients with partial thickness burn wounds and will provide evidence on the (cost-)effectiveness and quality of life of Flaminal® versus Flamazine® in the treatment of partial thickness burns.

Trial registration

Netherlands Trial Register NTR4486, registered on 2 April 2014.

Review of recent research on biomedical applications of electrospun polymer nanofibers for improved wound healing

Wound dressings play an important role in a patient's recovery from health problems, as unattended wounds could lead to serious complications such as infections or, ultimately, even death. Therefore, wound dressings since ancient times have been continuously developed, starting from simple dressings from natural materials for covering wounds to modern dressings with functionalized materials to aid in the wound healing process and enhance tissue repair. However, understanding the nature of a wound and the subsequent healing process is vital information upon which dressings can be tailored to ensure a patient's recovery. To date, much progress has been made through the use of nanomedicine in wound healing due to the ability of such materials to mimic the natural dimensions of tissue. This review provides an overview of recent studies on the physiology of wound healing and various wound dressing materials made of nanofibers fabricated using the electrospinning technique.

Antimicrobial Cellobiose Dehydrogenase-Chitosan Particles

Increasing prevalence of chronic wounds and microbial infection constitute a severe health challenge. The situation is further complicated by emerging multidrug resistance making the treatment of infections increasingly difficult. Here, a novel antimicrobial system based on in situ release of hydrogen peroxide (H2O2) by cellobiose dehydrogenase (CDH) immobilized on chitosan (CTS) particles is described. Covalent immobilization using carbodiimide coupling lead to a higher amount of protein immobilized on CTS (104 μg CDH/mg CTS) when compared to noncovalent immobilization, which, however, showed highest recovery of CDH activity (0.01 U/mg CTS). The CDH-CTS in situ generated H2O2 completely inhibited growth of Escherichia coli and Staphylococcus aureus over a period of 24 h. This resilient antimicrobial system represents a novel strategy for preventing infection with potential application in counteracting microbial colonization of chronic wounds.

Determination of Ag+ ions by a graphene oxide based dual-output nanosensor with high selectivity

A new highly selective chemosensor for Ag⁺ ions was designed and synthesized by covalently introducing well-known fluorophore 1,8-diaminonaphthalene (DAN) onto graphene oxide (GO) sheets.

Intracellular accumulation and dissolution of silver nanoparticles in L-929 fibroblast cells using live cell time-lapse microscopy

Cytotoxicity assessments of nanomaterials, such as silver nanoparticles, are challenging due to interferences with test reagents and indicators as well uncertainties in dosing as a result of the complex nature of nanoparticle intracellular accumulation. Furthermore, current theories suggest that silver nanoparticle cytotoxicity is a result of silver nanoparticle dissolution and subsequent ion release. This study introduces a novel technique, nanoparticle associated cytotoxicity microscopy analysis (NACMA), which combines fluorescence microscopy detection using ethidium homodimer-1, a cell permeability marker that binds to DNA after a cell membrane is compromised (a classical dead-cell indicator dye), with live cell time-lapse microscopy and image analysis to simultaneously investigate silver nanoparticle accumulation and cytotoxicity in L-929 fibroblast cells. Results of this method are consistent with traditional methods of assessing cytotoxicity and nanoparticle accumulation. Studies conducted on 10, 50, 100 and 200 nm silver nanoparticles reveal size dependent cytotoxicity with particularly high cytotoxicity from 10 nm particles. In addition, NACMA results, when combined with transmission electron microscopy imaging, reveal direct evidence of intracellular silver ion dissolution and possible nanoparticle reformation within cells for all silver nanoparticle sizes.

Acticoat™ stimulates inflammation, but does not delay healing, in acute full-thickness excisional wounds

Acticoat™ has antimicrobial and anti-inflammatory effects which aid wound healing. However, in vitro studies indicate that Acticoat™ is cytotoxic and clinical and in vivo studies suggest that it may delay healing in acute wounds. Therefore, this study investigated the effects of Acticoat™ on healing in acute full-thickness excisional wounds. Using a porcine model, healing was assessed on days 3, 6, 9 and 15 post-wounding. Five wounds dressed with Acticoat™ and five wounds dressed with polyurethane film (control) were assessed per day (n = 40 wounds). The rate of healing, inflammatory response, restoration of the epithelium and blood vessel and collagen formation were evaluated. No difference was found in the rate of healing between wounds treated with Acticoat™ and the control wounds. Inflammation was increased in Acticoat™-treated wounds on day 3 post-wounding compared to the control wounds. However, by day 15 post-wounding, the epithelium of the Acticoat™-treated wounds closely resembled normal epithelium. Acticoat™-treated wounds also contained a higher proportion of mature blood vessels, and differences in collagen deposition were apparent. Despite inducing an inflammatory response, Acticoat™ did not delay healing in acute wounds. Conversely, the improved quality of the epithelium and blood vessels within Acticoat™-treated wounds indicates that Acticoat™ has a beneficial effect on healing.

Boron and Poloxamer (F68 and F127) Containing Hydrogel Formulation for Burn Wound Healing

Burn injuries, the most common and destructive forms of wounds, are generally accompanied with life-threatening infections, inflammation, reduced angiogenesis, inadequate extracellular matrix production, and lack of growth factor stimulation. In the current study, a new antimicrobial carbopol-based hydrogel formulated with boron and pluronic block copolymers was evaluated for its healing activity using in vitro cell culture techniques and an experimental burn model. Cell viability, gene expression, and wound healing assays showed that gel formulation increased wound healing potential. In vitro tube-like structure formation and histopathological examinations revealed that gel not only increased wound closure by fibroblastic cell activity, but also induced vascularization process. Moreover, gel formulation exerted remarkable antimicrobial effects against bacteria, yeast, and fungi. Migration, angiogenesis, and contraction-related protein expressions including collagen, α-smooth muscle actin, transforming growth factor-β1, vimentin, and vascular endothelial growth factor were considerably enhanced in gel-treated groups. Macrophage-specific antigen showed an oscillating expression at the burn wounds, indicating the role of initial macrophage migration to the wound site and reduced inflammation phase. This is the first study indicating that boron containing hydrogel is able to heal burn wounds effectively. The formulation promoted burn wound healing via complex mechanisms including stimulation of cell migration, growth factor expression, inflammatory response, and vascularization.

Effect of Olea ointment and Acetate Mafenide on burn wounds - A randomized clinical trial

Background:

The main goals in treating burns are to accelerate tissue renovation and prevent infection. Topical antibiotics are used in the treatment of burns, but they can cause side effects. Recently, a traditional ointment (Olea) has been used in Iran in the treatment of burns. This study examines the effect of topical honey ointment in healing of burn patients.

Materials and Methods:

In this randomized controlled trial (RCT), 30 hospitalized patients selected by conventional sampling (10 in Olea group and 20 in Acetate Mafenide ointment group) were evaluated. Inclusion criteria were: having second-degree burns and body surface area equal to or < 40%. One group was treated using topical Olea ointment and the other with Acetate Mafenide ointment (8.5%). Chi-square, Fisher exact test, and Kaplan–Meier were used. Significance level was considered as P < 0.05.

Results:

None of the patients in the Olea group needed surgery for debridement, while in the second group, 13 patients (65%) needed debridement (P = 0.001). In the Olea group, 1 patient (10%) and in the second group, 19 patients (95%) had positive cultures after 7 days (P < 0.001). The mean time of granulation tissue formation in the Olea group was 12 days (10.3–13.6) and in the other group, it was 17 days (13.3–20.6) (P < 0.001).

Conclusions:

Olea ointment is a useful treatment for burns, and it can prevent infections, accelerate tissue repair, and facilitate debridement. Therefore, using this ointment is recommended for the treatment of burns.

Bacterial inhibition potential of 3D rapid-prototyped magnesium-based porous composite scaffolds--an in vitro efficacy study

Bone infections are common in trauma-induced open fractures with bone defects. Therefore, developing anti-infection scaffolds for repairing bone defects is desirable. This study develoepd novel Mg-based porous composite scaffolds with a basal matrix composed of poly(lactic-co-glycolicacid) (PLGA) and tricalcium phosphate (TCP). A unique low-temperature rapid prototyping technology was used to fabricate the scaffolds, including PLGA/TCP (PT), PLGA/TCP/5%Mg (PT5M), PLGA/TCP/10%Mg (PT10M), and PLGA/TCP/15%Mg (PT15M). The bacterial adhesion and biofilm formation of Staphylococcus aureus were evaluated. The results indicated that the Mg-based scaffolds significantly inhibited bacterial adhesion and biofilm formation compared to PT, and the PT10M and PT15M exhibited significantly stronger anti-biofilm ability than PT5M. In vitro degratation tests revealed that the degradation of the Mg-based scaffolds caused an increase of pH, Mg(2+) concentration and osmolality, and the increased pH may be one of the major contributing factors to the antibacterial function of the Mg-based scaffolds. Additionally, the PT15M exhibited an inhibitory effect on cell adhesion and proliferation of MC3T3-E1 cells. In conclusion, the PLGA/TCP/Mg scaffolds could inhibit bacterial adhesion and biofilm formation, and the PT10M scaffold was considered to be an effective composition with considerable antibacterial ability and good cytocompatibility.

Evidence-Based Approach to Advanced Wound Care Products

There is increasing pressure from industry to use advanced wound care products and technologies. Many are very expensive but promise to reduce overall costs associated with wound care. Compelling anecdotal evidence is provided that inevitably shows wounds that failed all other treatments but responded positively to the subject product. Evidence-based medicine is the standard by which physician-scientists must make their clinical care decisions. In an attempt to provide policy makers with the most current evidence on advanced wound care products, the Department of Veteran Affairs conducted an Evidence-based Synthesis Program review of advanced wound care products. This paper suggests how to take this information and apply it to policy to drive evidence-based care to improve outcomes and fiduciary responsibility.

Emerging Trends in Abdominal Wall Reinforcement: Bringing Bio-Functionality to Meshes

Abdominal wall hernia is a recurrent issue world-wide and requires the implantation of over 1 million meshes per year. Because permanent meshes such as polypropylene and polyester are not free of complications after implantation, many mesh modifications and new functionalities have been investigated over the last decade. Indeed, mesh optimization is the focus of intense development and the biomaterials utilized are now envisioned as being bioactive substrates that trigger various physiological processes in order to prevent complications and to promote tissue integration. In this context, it is of paramount interest to review the most relevant bio-functionalities being brought to new meshes and to open new avenues for the innovative development of the next generation of meshes with enhanced properties for functional abdominal wall hernia repair.

Topical antibiotic ointment versus silver-containing foam dressing for second-degree burns in swine

OBJECTIVES

Second-degree burns are very common but their management is controversial. These burns may be treated with either topical antimicrobial agents or advanced occlusive dressings; however, there is no established treatment comparator for preclinical studies. This study was designed to determine which of two commonly used comparator therapies (a silver-containing advanced dressing or a topical antibiotic ointment) resulted in faster reepithelialization and less scarring. The hypothesis was that second-degree burns treated with a topical antimicrobial ointment would heal faster and with less scarring than those treated with a silver-containing occlusive foam dressing in a porcine model.

METHODS

Deep partial-thickness burns were created on the flanks of three anesthetized female domestic pigs (20 to 25 kg) using a 150-g aluminum bar preheated in 80°C water bath and applied to the skin for 20 seconds using a force of 2 kg. The burn eschars were excised 48 hours later with an electric dermatome set at a depth of 0.75 mm. The wound beds were treated with a thin layer of triple-antibiotic petrolatum-based ointment (changed three times weekly) or a silver-containing foam dressing (changed once weekly). Full-thickness punch biopsies were obtained at 9, 11, 14, 16, 18, and 21 days for determination of percentage complete wound reepithelialization and at 28 days for measurement of scar depth.

RESULTS

At all dressing changes the wounds treated with the topical antibiotic appeared moist, while those treated with the silver-based dressings appeared dry. At day 21 all wounds treated with the ointment were completely reepithelialized, while only 55% of those treated with the silver dressing were reepithelialized (p < 0.001). Scar depth at day 28 was also significantly less in wounds treated with the topical antibiotic ointment (4.3 mm vs. 5.1 mm, difference = 0.7 mm; 95% confidence interval [CI] = 0.1 to 1.4 mm). There was less scar contraction in wounds treated with the topical antibiotic compared with the silver-based dressing (mean ± SD = 25.0% ± 14.6% vs. 38.9% ± 16.9%, difference = 13.9%; 95% CI = 5.7% to 22.0%).

CONCLUSIONS

In this model of excised deep partial-thickness burns, a triple-antibiotic ointment enhanced reepithelialization and reduced scar depth and contraction compared with a silver-based foam dressing. This triple-antibiotic ointment should be considered as a control for studies evaluating novel topical burn therapies.

Hybrid wound dressings with controlled release of antibiotics: Structure-release profile effects and in vivo study in a guinea pig burn model

Over the last decades, wound dressings have evolved from a crude traditional gauze dressing to tissue-engineered scaffolds. Many types of wound dressing formats are commercially available or have been investigated. We developed and studied hybrid bilayer wound dressings which combine a drug-loaded porous poly(dl-lactic-co-glycolic acid) top layer with a spongy collagen sublayer. Such a structure is very promising because it combines the advantageous properties of both layers. The antibiotic drug gentamicin was incorporated into the top layer for preventing and/or defeating infections. In this study, we examined the effect of the top layer's structure on the gentamicin release profile and on the resulting in vivo wound healing. The latter was tested on a guinea pig burn model, compared to the neutral non-adherent dressing material Melolin® (Smith & Nephew) and Aquacel® Ag (ConvaTec). The release kinetics of gentamicin from the various studied formulations exhibited burst release values between 8% and 38%, followed by a drug elution rate that decreased with time and lasted for at least 7 weeks. The hybrid dressing, with relatively slow gentamicin release, enabled the highest degree of wound healing (28%), which is at least double that obtained by the other dressing formats (8-12%). It resulted in the lowest degree of wound contraction and a relatively low amount of inflammatory cells compared to the controls. This dressing was found to be superior to hybrid wound dressings with fast gentamicin release and to the neat hybrid dressing without drug release. Since this dressing exhibited promising results and does not require frequent bandage changes, it offers a potentially valuable concept for treating large infected burns.

The Anti-Inflammatory and Antibacterial Action of Nanocrystalline Silver and Manuka Honey on the Molecular Alternation of Diabetic Foot Ulcer: A Comprehensive Literature Review

Honey and silver have been used since ancient times for treating wounds. Their widespread clinical application has attracted attention in light of the increasing prevalence of antibiotic-resistant bacteria. While there have been a number of studies exploring the anti-inflammatory and antibacterial effects of manuka honey and nanocrystalline silver, their advantages and limitations with regard to the treatment of chronic wounds remain a subject of debate. The aim of this paper is to examine the evidence on the use of nanocrystalline silver and manuka honey for treating diabetic foot ulcers through a critical and comprehensive review of in vitro studies, animal studies, and in vivo studies. The findings from the in vitro and animal studies suggest that both agents have effective antibacterial actions. Their anti-inflammatory action and related impact on wound healing are unclear. Besides, there is no evidence to suggest that any topical agent is more effective for use in treating diabetic foot ulcer. Overall, high-quality, clinical human studies supported by findings from the molecular science on the use of manuka honey or nanocrystalline silver are lacking. There is a need for rigorously designed human clinical studies on the subject to fill this knowledge gap and guide clinical practice.

Effect of piracetam and nimodipine on full-thickness skin burns in rabbits

The potential of several drugs for full-thickness skin burns has been investigated, but the treatment of such burns remains a challenge in plastic surgery. The present study was designed to determine the effect of systemic and topical administration of piracetam and nimodipine on full-thickness skin burn wound healing. A total of 36 New Zealand male rabbits were divided into six groups. Full-thickness skin burns were produced in all the groups, except the control group. Piracetam was administered systemically (piracetam-IV) and topically (piracetam-C) for 14 days, and nimodipine was administered systemically (nimodipine-IV) and topically (nimodipine-C) over the burn wounds for 14 days. The sham group underwent burn injury but was not administered any drug. After 21 days, gross examination and histopathological analysis were performed and the results were compared statistically. Nimodipine-C and nimodipine-IV had no effect on burn wound healing. However, both piracetam-IV and piracetam-C significantly enhanced the healing of the full-thickness skin burn wounds, although the latter was more effective, useful and practical in burn wound healing. The histopathological features of the wounds in the piracetam-C group were closer to those of the control group than those of the other groups. Piracetam-C rather than piracetam-IV may promote full-thickness burn wound healing in rabbits.

Advances in skin regeneration: application of electrospun scaffolds

The paucity of cellular and molecular signals essential for normal wound healing makes severe dermatological ulcers stubborn to heal. The novel strategies of skin regenerative treatments are focused on the development of biologically responsive scaffolds accompanied by cells and multiple biomolecules resembling structural and biochemical cues of the natural extracellular matrix (ECM). Electrospun nanofibrous scaffolds provide similar architecture to the ECM leading to enhancement of cell adhesion, proliferation, migration and neo tissue formation. This Review surveys the application of biocompatible natural, synthetic and composite polymers to fabricate electrospun scaffolds as skin substitutes and wound dressings. Furthermore, the application of biomolecules and therapeutic agents in the nanofibrous scaffolds viz growth factors, genes, antibiotics, silver nanoparticles, and natural medicines with the aim of ameliorating cellular behavior, wound healing, and skin regeneration are discussed.