A literature review of the military uses of silver-nylon dressings with emphasis on wartime operations

Evaluation of Topical Off-the-Shelf Therapies to Reduce the Need to Evacuate Battlefield-Injured Warfighters

INTRODUCTION

Immediate evacuation of burn casualties can be challenging in austere environments, and it is predicted to be even more difficult in future multi-domain battlespaces against near-peer foes. Therefore, a need exists to treat burn wounds at the point of injury to protect the exposed injury for an extended period. In this study, we compare two commercially available FDA-approved therapies to the current gold standard of care (GSOC), excisional debridement followed by the application of split-thickness skin graft, and the standard for prolonged field care, silver sulfadiazine (SSD) cream. The shelf-stable therapies evaluated were irradiated human skin (IHS) allograft and polylactic acid (PLA). Our objective was to study whether they have the potential capability to reduce the need for evacuation to a burn center for surgical intervention so that the combat power can be preserved in the field.

MATERIALS AND METHODS

Sixteen burns (50 cm2) were created on the dorsum of four anesthetized swine. All materials were sterile, but a sterile field was not utilized in order to simulate the prolonged field care setting. The wounds were then treated with PLA, IHS, and SSD cream, and the remaining wounds (designated GSOC) were also treated with SSD cream. On post-operative day (POD) 3, sterile surgical debridement and skin grafting (1:4) were performed on the GSOC wounds. Burn healing was followed for either PODs 10, 14, 21, or 28, wherein one animal was humanely euthanized at each time point; each represented a time point of the healing process. A full-thickness excisional biopsy was taken from each wound immediately after euthanasia to give a cross-section view of the wound edge to edge. Wound healing was determined by the histological analysis of wound re-epithelialization, epidermal thickness, rete ridges, and scar elevation index and macroscopically using noninvasive imaging systems.

RESULTS

The PLA and IHS treatments did not need to be reapplied to the wounds during the course of the experiment, unlike SSD, which was reapplied at each assessment time point. In terms of re-epithelialization, on POD 10, IHS and SSD were similar to the GSOC; on POD 14, all treatments were similar; on POD 21, PLA and IHS were similar to SSD; finally, on POD 28, re-epithelialization was similar in all groups. On POD 28, scar elevation index and rete ridges/mm were similar to all groups, and epidermal and dermal thickness for PLA and IHS were similar to GSOC.

CONCLUSIONS

This preclinical study demonstrated that the use of the PLA and the IHS dressings resulted in similar outcomes to the GSOC-treated burns in several key metrics of wound healing. These therapies represent a potentially useful tool in current and future battlespaces, where surgical intervention is not possible. The products are lightweight and, more importantly, stable at room temperature for their entire shelf lives. This would allow for easy storage and transport by medical practitioners in the field.

Skin Models Used to Define Mechanisms of Action of Sulfur Mustard

Sulfur mustard (SM) is a threat to both civilian and military populations. Human skin is highly sensitive to SM, causing delayed erythema, edema, and inflammatory cell infiltration, followed by the appearance of large fluid-filled blisters. Skin wound repair is prolonged following blistering, which can result in impaired barrier function. Key to understanding the action of SM in the skin is the development of animal models that have a pathophysiology comparable to humans such that quantitative assessments of therapeutic drugs efficacy can be assessed. Two animal models, hairless guinea pigs and swine, are preferred to evaluate dermal products because their skin is morphologically similar to human skin. In these animal models, SM induces degradation of epidermal and dermal tissues but does not induce overt blistering, only microblistering. Mechanisms of wound healing are distinct in these animal models. Whereas a guinea pig heals by contraction, swine skin, like humans, heals by re-epithelialization. Mice, rats, and rabbits are also used for SM mechanistic studies. However, healing is also mediated by contraction; moreover, only microblistering is observed. Improvements in animal models are essential for the development of therapeutics to mitigate toxicity resulting from dermal exposure to SM.

Evaluation of Topical Off-The-Shelf Therapies to Improve Prolonged Field Care of Burn-Injured Service Members

INTRODUCTION

Burns are common injuries on the battlefield. Given austere environments, surgical debridement of injured service members is often not feasible in these settings. Delays in surgical debridement create a risk of infection and deranged healing for burn patients. As such, this study attempts to identify the best commercially available off-the-shelf (OTS) therapies with field-deployable potential to improve prolonged field care (PFC) of burn-injured soldiers.

METHODS

Deep partial-thickness (DPT) burns (25 cm2) were created on the dorsum of 5 anesthetized pigs utilizing a thermocouple burn device at 100°C for 15 seconds. Nonsurgical debridement was done 1-hour after burn creation using sterile saline water and gauze to remove excess eschar tissue. Animals were then randomized into 5 experimental groups, and OTS therapies were applied to 6 of the 12 created DPT burns. The remaining 6 burns were treated with 1% silver sulfadiazine cream (Ascend Laboratories, LLC, Parsippany, NJ) as the PFC standard of care (SOC) controls. The 5 randomized OTS therapies were: irradiated sterile human skin allograft (IHS), biodegradable temporizing matrix (BTM), polylactic acid skin substitute, hyaluronic acid ester matrix (HAM), and decellularized fish skin graft (FSG). Wounds were serially assessed on post-burn days 3, 7, 14, 21, and 28. Assessments were conducted using a combination of photographs, histology, and quantitative bacteriology. Endpoints included burn wound progression, re-epithelialization, wound contraction, scar elevation index, and colony-forming units (CFU).

RESULTS

The analysis demonstrated that by day 3, the FSG prevented burn wound progression the most efficiently. In terms of wound healing, the results showed re-epithelialization percentages close to 100% by day 28 for all treatment groups. No statically significant differences were observed. Quality of healing analyses demonstrated that the BTM-treated wounds had contracted less and the difference to the IHS-treated wounds was statistically significant (P < .05). As regards to antimicrobial properties, the CFU results showed no statistically significant differences between the OTS therapies and the SOC on days 3, 7, and 14.

CONCLUSIONS

The impact of Food and Drug Administration-approved OTS therapies was compared to the current PFC SOC for the treatment of DPT burns in a porcine model. Several topical options exist for the management of burns prior to definitive treatment in the operating room and warrant further evaluation. These therapies are actively used on civilian burn counterparts and have far-forward, field-deployable potential for use at the point of injury so that injured service members may not need evacuation to higher roles of care and combat power may be preserved. Our results demonstrated that all the studied OTS therapies performed well when compared to the SOC in terms of burn wound progression, wound healing, quality of healing, and quantitative bacteriology.

Nanocomposite Hydrogel Films Based on Sequential Interpenetrating Polymeric Networks as Drug Delivery Platforms

In this study, novel materials have been obtained via a dual covalent and ionic crosslinking strategies, leading to the formation of a fully interpenetrated polymeric network with remarkable mechanical performances as drug delivery platforms for dermal patches. The polymeric network was obtained by the free-radical photopolymerization of N-vinylpyrrolidone using tri(ethylene glycol) divinyl ether as crosslinker in the presence of sodium alginate (1%, weight%). The ionic crosslinking was achieved by the addition of Zn2+, ions which were coordinated by the alginate chains. Bentonite nanoclay was incorporated in hydrogel formulations to capitalize on its mechanical reinforcement and adsorptive capacity. TiO2 and ZnO nanoparticles were also included in two of the samples to evaluate their influence on the morphology, mechanical properties and/or the antimicrobial activity of the hydrogels. The double-crosslinked nanocomposite hydrogels presented a good tensile resistance (1.5 MPa at 70% strain) and compression resistance (12.5 MPa at a strain of 70%). Nafcillin was loaded into nanocomposite hydrogel films with a loading efficiency of up to 30%. The drug release characteristics were evaluated, and the profile was fitted by mathematical models that describe the physical processes taking place during the drug transfer from the polymer to a PBS (phosphate-buffered saline) solution. Depending on the design of the polymeric network and the nanofillers included, it was demonstrated that the nafcillin loaded into the nanocomposite hydrogel films ensured a high to moderate activity against S. aureus and S. pyogenes and no activity against E. coli. Furthermore, it was demonstrated that the presence of zinc ions in these polymeric matrices can be correlated with the inactivation of E. coli.

Beyond nylon 6: polyamides via ring opening polymerization of designer lactam monomers for biomedical applications

Ring opening polymerization (ROP) of lactams is a highly efficient and versatile method to synthesize polyamides. Within the last ten years, significant advances in polymerization methodology and monomer diversity are ushering in a new era of polyamide chemistry. We begin with a discussion of polymerization techniques including the most widely used anionic ring opening polymerization (AROP), and less prevalent cationic ROP and enzyme-catalyzed ROP. Next, we describe new monomers being explored for ROP with increased functionality and stereochemistry. We emphasize the relationships between composition, structure, and properties, and how chemists can control composition and structure to dictate a desired property or performance. Finally, we discuss biomedical applications of the synthesized polyamides, specifically as biomaterials and pharmaceuticals, with examples to include as antimicrobial agents, cell adhesion substrates, and drug delivery scaffolds.

Cerium Nitrate Treatment in the Management of Burns

Significance: The standard of care for deep burn wounds is eschar excision and autologous skin grafting within the first postburn days. However, when this is not practical due to medical reasons, unavailable surgical facilities, or lack of donor sites or other coverage, surgeons have used topical cerium nitrate (CN) in a cream with silver sulfadiazine (SSD) for over four decades to convert the eschar into a pliable and protective crust that facilitates the postponement or staging of eschar excision and grafting. CN+SSD treatment is reported to reduce dressing changes, improve patient comfort, and reduce bacterial burden, with unaffected epithelialization and few complications. Recent Advances: CN aqueous solutions applied topically alone or together with solid silver dressings in animal models have mitigated wound injury progression, wound microbial burden, and systemic immune dysfunction. Critical Issues: CN+SSD cream is not approved by U.S. Food and Drug Administration (FDA) and its efficacy in clinical trials has been challenging to demonstrate. One reason is that CN changes the eschar visibly, introducing unavoidable bias. Also, the market and patient population is small and burn wound presentation is highly variable. Future Directions: For use in settings wherein the once- or twice-daily CN+SSD cream dressing changes are least feasible (low-income, military, and mass casualty settings), it may be possible to develop a solid dressing containing cerium and silver that requires infrequent dressing changes. For future clinical studies, the trial design most suited to comparing silver-containing dressings with and without cerium may be paired difference of matched intrapatient wounds.

Preclinical Study of a Multi-Layered Antimicrobial Patch Based on Thin Nanocomposite Amorphous Diamond Like Carbon Films with Embedded Silver Nanoparticles

A growing number of severe infections are related to antibiotic-resistant bacteria, therefore, in recent years, alternative antimicrobial materials based on silver nanoparticles (NPs) attracted a lot of attention. In the current research, we present a medical patch prototype containing diamond-like carbon nanocomposite thin films doped with silver nanoparticles (DLC:Ag), as a source of silver ions, and an aqueous mass of the gelatin/agar mixture as a silver ion accumulation layer. The DLC:Ag thin films with 3.4 at.% of silver were deposited on synthetic silk employing reactive unbalanced DC magnetron sputtering of the silver target with argon ions performed in the acetylene gas atmosphere. The average size of the silver nanoparticles as defined by scanning electron microscope was 24 nm. After the film deposition, the samples were etched with RF oxygen plasma, aiming at efficient silver ion release in aqueous media from the nanocomposite film. In the patch prototype, a mixture of agar and gelatin was applied in silicone carrier with cavities, acting as a silver ion accumulation layer that further enhanced the antimicrobial efficiency. It was found that the DLC:Ag thin film on the silk after soaking in water for 24 h was able to release up to 4 ppm of Ag. The microbiological experiments using S. aureus bacteria were performed with the patch prototype and the silver ion saturated water, demonstrated the inactivation of 99% and 79% of bacteria, respectively. Scanning electron microscopy analysis showed that silver NPs destroyed the bacteria cell and the bacteria affected by Ag ions had spots and perforated cell wall areas with cytoplasm leakage out was obtained. A preliminary preclinical study using the laboratory animals demonstrated that using the patch prototype, the methicillin-resistant S. aureus (MRSA)-infected wound on skin surface healed faster compared with control and was able to kill all MRSA bacteria strains in the wound's bed after 72 h of treatment.

Advances in treatment of acute sulfur mustard poisoning - a critical review

Sulfur mustard (SM) is a blistering chemical warfare agent that was used during the World War I and in the Iraq-Iran conflict. The aim of this paper is to discuss and critically review the published results of experiments on the treatment of SM poisoning based on our clinical and research experience. The victims must remove from the contaminated zone immediately. The best solution for decontamination is large amounts of water, using neutral soap and 0.5% sodium hypochlorite. Severely intoxicated patients should be treated according to advanced life support protocols and intensive care therapy for respiratory disorders and the chemical burn. Sodium thiosulfate infusion (100-500 mg/kg/min) should be started up to 60 min after SM exposure. However, N-acetyle cysteine (NAC) is recommended, none of them acts as specific or effective antidote. The important protective and conservative treatment of SM-induced pulmonary injuries include humidified oxygen, bronchodilators, NAC as muculytic, rehydration, mechanical ventilation, appropriate antibiotics and respiratory physiotherapy as clinically indicated. Treatment of acute SM ocular lesions start with topical antibiotics; preferably sulfacetamide eye drop, continue with lubricants, and artificial tears. Treatment for cutaneous injuries include: moist dressing; preferably with silver sulfadiazine cream, analgesic, anti-pruritic, physically debridement, debridase, Laser debridement, followed by skin autologous split-thickness therapy as clinically indicated. The new suggested medications and therapeutic approaches include: anti-inflammatory agents, Niacinamide, Silibinin, Calmodulin antagonists, Clobetasol, full-thickness skin grafting for skin injuries; Doxycycline; Bevacizumab, and Colchicine for ocular injuries. Recommended compounds based on animal studies include Niacinamide, Aprotinin, des-aspartate-angiotensin-I, Gamma-glutamyltransferase, vitamin E, and vitamin D. In vitro studies revealed that Dimethylthiourea, L-nitroarginine, Methyl-ester, Sodium pyruvate, Butylated hydroxyanisole, ethacrynic acid, and macrolide antibiotics are effective. However, none of them, except macrolide antibiotics have been proved clinically. Avoidance of inappropriate polypharmacy is advisable.

Safety evaluation of silver-ion dressings in a porcine model of deep dermal wounds: A GLP study

INTRODUCTION

Silver ion has strong antimicrobial properties and is used in a number of wound dressings. In burn models, silver-nylon dressings produce elevated silver levels in the wound along with minimal systemic effect. We evaluated systemic toxicity in a non-burn wound model to see if a similar pattern of silver ion distribution would occur.

METHODS

Eight deep partial-thickness wounds each were created on the dorsum of 40 Gottingen minipigs using a Er-YAG Laser. Half were treated with a 21-day course of silver-nylon dressings (Silverlon®) and half were treated with moist gauze dressings. Wound, blood, liver and kidney silver levels, along with blood chemistry and hematology data were obtained at appropriate intervals.

RESULTS

All wounds healed well with healing enhanced by silver-nylon dressings. Silver ion was demonstrable in all wounds treated with silver-nylon at day 21 and after 14 days of no further treatment. Silver ion was not detected in blood, liver or kidney of any animal treated with silver-nylon or control dressings. Liver and kidney function remained normal in all animals.

CONCLUSION

A 21-day application of silver-nylon dressings to a non-burn dermal wound produces no systemic or local toxicity in Gottingen minipigs.

Silver, biofilms and wounds: resistance revisited

Silver is added to an array of commercially available healthcare products including wound dressings. However, overuse of silver is being raised as a potential health concern due to the possible selection of tolerant or resistant bacteria and as a factor that may induce cross resistance to antibiotics. To date, there are only a limited number of studies that have documented evidence of silver resistance in bacteria isolated from medical situations. These studies have indicated low levels of silver resistance in bacteria. However, in comparison to antibiotics, only a small number of studies have been undertaken to investigate silver resistance. It is clear that more studies are required to confirm the most effective therapeutic levels of silver that are needed to kill microbes. In addition, it is probable that sub-therapeutic levels of silver may potentially select for enhanced microbial tolerance. Nevertheless, to date, there still remains very little evidence that silver resistance is a growing health concern in wound care; more studies are clearly needed to substantiate this concern, which has not been observed clinically to any major degree. The issue of biofilm tolerance to silver is more complicated and data on the effect of silver on biofilms is sparse at present.

Resistant Gram-Negative Bacteria and Diagnostic Point-of-Care Options for the Field Setting during Military Operations

The spread of multidrug-resistant bacteria in resource-poor settings affects the military medical service in case of deployments of soldiers to war and crisis zones. Patients with war injuries are prone to colonization or infection with multidrug-resistant bacteria. Resistant Gram-negative bacteria play a dominant role in military wound infections. Problematic hygiene conditions on deployment facilitate exposition of soldiers with subsequent colonization. Although colonizing strains are frequently cleared from their hosts after returning from deployment, transmission to close contacts of the soldiers in the home country cannot be excluded and therapeutic options are reduced if colonization progresses to invasive infection. Since sophisticated culture-based diagnostic approaches are typically not available in the field setting on deployment, molecular rapid diagnostic test systems are an option for transmission control if the locally prevalent molecular resistance mechanisms are known. Efforts for global resistance surveillance can contribute to better understanding of resistance distribution and spread at deployment sites. This review summarizes experience of the military medical services with multidrug resistance on deployment and with the influx of resistant strains to the home country and discusses potential use of available molecular rapid test systems as an option for the field setting.

Blood and Tissue Silver Levels Following Application of Silver-Based Dressings to Sulfur Mustard Chemical Burns

Silver-based dressings are commonly used in burn care. Silver sulfadiazine use is associated with elevated blood, urine, and tissue levels of silver ion. We examined wound and tissue levels of silver ion in a two-species model of sulfur mustard chemical burn injury treated with two different silver-based dressings. Superficial dermal and moderate thickness dermal chemical burns were induced in 16 hairless guinea pigs and in 16 Gottingen minipigs by exposure to sulfur mustard vapor. After debridement, silver-nylon burn dressings or silver-calcium alginate dressings were applied and changed every 7 days until wound healing or a maximum of 60 days post exposure. At autopsy, liver, spleen, and wound samples were harvested. Silver ion was measured using inductively coupled plasma-mass spectrography with a lower level of detection of 0.02 parts per billion. Negligible silver ion levels were found in the liver (mean < 0.003 μg/g of tissue) and spleen (mean < 0.05 μg/g) of all 32 animals. Wound biopsies showed silver ion levels ranging from 0.07 to 19.5 μg/g of tissue. Wound levels were higher in minipigs than in hairless guinea pigs and were higher in animals treated with silver-nylon burn wound dressings than with silver-calcium alginate dressings. Silver ion could be detected in some wounds 40 days after dressings were removed. In a chemical burn model, application of silver-nylon or silver-calcium alginate dressings is associated with elevated wound levels but negligible tissue levels of silver ion.

Burn Wound Healing and Tissue Engineering

In 2016 the American Burn Association held a State of the Science conference to help identify burn research priorities for the next decade. The current paper summarizes the work of the sub-committee on Burn Wound Healing and Tissue Engineering. We first present the priorities in wound healing research over the next 10 years. We then summarize the current state of the science related to burn wound healing and tissue engineering including determination of burn depth, limiting burn injury progression, eschar removal, management of microbial contamination and wound infection, measuring wound closure, accelerating wound healing and durable wound closure, and skin substitutes and tissue engineering. Finally, a summary of the round table discussion is presented.

Lessons Learned from Burn Disasters in the Post-9/11 Era

Although every disaster scenario is unique, certain themes have emerged repeatedly during management of burn disasters. These lessons learned are useful when planning an individual burn unit's role in future disaster response.

Silver in medicine: the basic science

Silver compounds are increasingly used in medical applications and consumer products. Confusion exists over the benefits and hazards associated with silver compounds. In this article, the biochemistry and physiology of silver are reviewed with emphasis on the use of silver for wound care.