Effects of Silver Nanoparticles on Burn Wound Healing in a Mouse Model.

Healing of injuries caused by exposure to heat has been discussed in many studies, although a few drugs have been shown to produce satisfactory results. In this study, 100 healthy mice randomly allocated into four categories (each = 25 mice) were analyzed. A deep second-degree burn on the back of each mouse was created. The burns were dressed daily with either AgNPs or silver sulfadiazine over 28 days of treatment. Safety evaluation of the AgNP treatment was performed by measuring the deposition rate of silver in the liver, brain, and kidney of treated mice. In the murine burn model, the speed of wound healing and the antibacterial effect of AgNPs were better than those in the silver sulfadiazine group. Burn wounds treated with SSD appeared to display a greater degree of inflammation as notable by the three clinical signs of the inflammatory process such as redness and swelling which appeared to be less after wounds treated with AgNPs. Also, AgNP treatment modified leukocytic infiltration and reduced collagen degeneration in treated mice and enhanced healing processes that were confirmed by morphological and histological investigations. Beside the potential significant effects of AgNPs on reduction of some microorganism counts that routinely isolated from burn wounds included aerobic organisms as Staphylococcus aureus and Escherichia coli when compared to both SSD and control groups. The deposition kinetics of AgNPs revealed lower distribution in the liver, brain, and kidney than that in silver sulfadiazine-treated mice with respect to both SSD and control groups.

Development and evaluation of silver sulfadiazine loaded microsponge based gel for partial thickness (second degree) burn wounds.

Silver sulfadiazine has been frequently used as an antibacterial agent for topical treatment of partial thickness burn wounds. In this study, we present the preparation of silver sulfadiazine microsponges by w/o/w emulsion solvent evaporation method. Formulation variables were optimized by using 32 factorial design. The optimized microsponges were characterized by FTIR, DSC, PXRD, particle size analysis, SEM analysis and mercury intrusion porosimetry studies. Viscosity, texture analysis and ex vivo drug deposition study of optimized microsponge loaded gel were also evaluated. The safety of the optimized gel was assessed by MTT assay using epidermal keratinocyte (HaCaT) and mouse embryonic fibroblast (NIH-3T3) cell lines. In vitro antibacterial studies were carried out to compare the antibacterial inhibitory efficiency of the optimized gel against the commercial product. The efficacy of the optimized gel was evaluated by the partial thickness (second degree) burn wound model in mice. Optimized microsponge loaded gel enhanced the drug retaining capacity in the skin layers, by 3 fold higher to that of a commercial product. The antibacterial inhibitory efficiency of optimized gel was similar to the commercial product against the Staphylococcus aureus and Pseudomonas aeruginosa. Optimized gel showed reduced frequency of application, no skin irritation, low cytotoxicity on dermal cell lines and enhanced wound contraction.

Falsely raised whole blood chloride caused by systemic absorption of cerium nitrate cream for burns.

Whole blood, serum or plasma chloride is almost exclusively measured by potentiometry with an ion-selective chloride electrode which utilizes membrane selectivity to chloride ions. Other anions such as bromide, iodide and thiosulphate can interfere but usually are not present in high enough concentration to cause significant cross reactivity. A patient from our burns unit had serial chloride measurements on a Radiometer ABL800 blood gas analyser. The results were higher in contrast to plasma measurements on the Abbott Architect Ci8200, which were within reference intervals and in line with the patient's pathophysiological status. This indicated a likely interference with the blood gas analyser chloride estimation. The chloride results on the ABL800 for 3rd, 4th and 5th day after the burn accident were 170, 137 and 119 mmol/L. Corresponding plasma chloride results on the Ci8200 were all around 105 mmol/L. Nitrate was found to be markedly elevated in these samples, and the results were 6.7, 4.9 and 1.1 mmol/L, respectively (reference limit < 0.08 mmol/L). To further demonstrate nitrate was the causative agent, pooled plasma spiked with 7 mmol/L of sodium nitrate caused a rise in the ABL800 chloride from 105 to 202 mmol/L. Later we confirmed that the patient was topically medicated with cerium nitrate cream (Flammacerium®, Sinclair IS Pharma, UK) for his burns. In summary, the results clearly indicated nitrate was the interferent with the ABL800 chloride estimation and the source was the topical burns cerium nitrate cream.

Nanoscalic silver possesses broad-spectrum antimicrobial activities and exhibits fewer toxicological side effects than silver sulfadiazine.

Silver has been used successfully for decades as an antibacterial agent and has become a standard treatment for burns and bacterial skin infections. Silver-containing creams, particularly silver sulfadiazine (SSD), possess effective activities against bacteria and fungi. However, there is serious concern that silver ions applied to denuded skin might be absorbed in significant amounts, thus introducing the risk of silver deposition, potentially leading to internal organ injury. In view of these facts we compared the percutaneous absorption and the antimicrobial potency of SSD with a new composition, nanoscalic silver (NSAg). In a murine model topical application of NSAg resulted in significantly lower percutaneous absorption and internal organ deposition compared to SSD. Strikingly, antimicrobial activity of NSAg used as a 0.1% formulation was comparable not only with 0.1% SSD against different bacterial strains including methicillin-resistant Staphylococcus aureus, but also against different yeast and dermatophyte species. FROM THE CLINICAL EDITOR: Nanoscale silver (NSAg) was demonstrated to have significantly lower percutaneous absorption and less accumulation in multiple organs when applied to denuded skin. Its antimicrobial activity against MRSA was not only comparable to silver sulfadiazine, but the formulation was also effective against different yeast and dermatophyte species.

Conservative management of exomphalos major with silver dressings: are they safe?

Historically, some dressings used in exomphalos major were associated with toxicity. These have been abandoned in favor of safer dressings. Silver toxicity has not been described following the use of silver dressings in infants. We, however, found disconcerting serum silver levels in 2 consecutive patients during treatment with silver salt containing dressings.

Drug release kinetics and transport mechanisms from semi-interpenetrating networks of gelatin and poly(ethylene glycol) diacrylate.

PURPOSE: To elucidate the key parameters affecting solute transport from semi-interpenetrating networks (sIPNs) comprised of poly(ethylene glycol) diacrylate (PEGdA) and gelatin that are partially crosslinked, water-swellable and biodegradable. Effects of material compositions, solute size, solubility, and loading density have been investigated. MATERIALS AND METHODS: sIPNs of following gelatin/PEGdA weight-to-weight ratios were prepared: 10:15, 10:20, 10:30, 15:15, 20:15. Five model solutes of different physicochemical properties were selected, i.e. silver sulfadiazine (AgSD), bupivacaine hydrochloride (Bup), sulfadiazine sodium (NaSD), keratinocyte growth factor (KGF), and bovine serum albumin conjugated with fluorescein isothiocyanate (BSA-FITC). Release studies were performed and the results were analyzed using three hydrogel based common theories (free volume, hydrodynamic and obstruction). RESULTS: The release kinetics of model solutes was influenced by each factor under investigation. Specifically, the initial release rates and intra-gel diffusivity decreased with increasing PEGdA content or increasing solute molecular weight. However, the initial release rate and intra-gel diffusivity increased with increasing gelatin content or increasing solute water solubility, which contradicted with the classical hydrogel based solute transport theories, i.e. increasing polymer volume leads to decreased solute diffusivity within the gel. CONCLUSION: This analysis provides structure-functional information of the sIPN as a potential therapeutic delivery matrix.

Enhancement effect of terpenes on silver sulphadiazine permeation through third-degree burn eschar.

Antimicrobial therapy remains one of the most important methods of wound management. Systemically administered antimicrobials may not achieve therapeutic levels in wound and most agents cannot penetrate burn eschar well enough when applied topically. Therefore, we tested the notion to increase permeability of eschar toward topical agents using terpenes, a well-known class of skin permeation enhancers. Four terpenes, limonene (hydrocarbon), eucalyptol (ether), alpha-pinene oxide (epoxide) and geraniol (alcohol) were chosen and their effects on permeation of silver sulphadiazine (SSD), a widely used topical antimicrobial agent, through human third-degree burn eschar was evaluated using static diffusion cells. Results showed that terpenes increased permeation flux of SSD through eschar significantly (P<0.0001). Limonene provided the highest flux enhancement ratio (9.0 times), followed by geraniol, eucalyptol and alpha-pinene oxide with enhancement ratios of 5.5, 4.7 and 4.3 respectively. The effects of terpenes on permeation lag-time, was less than 20%. Data analysis revealed that terpenes increase permeation of SSD mainly by increasing its partitioning into the eschar. The present results show that permeation of drugs through burn eschar can be increased considerably by terpenes and that burn wound antimicrobial therapy may be improved by terpenes and possibly other penetration enhancers.

The side effects of silver sulfadiazine.

Silver sulfadiazine cream has an enviable safety record in burn treatment. However, it side effects, exemplified by allergic reactions to its sulfadiazine moiety, silver staining of the treated burn wound, hyperosmolality, methemoglobinemia, and hemolysis due to a congential lack of glucose-6-phospate dehydrogenase, may be missed or misinterpreted. Early post burn leukopenia, once thought to be a side effect of the use of silver sulfadiazine in burn wound therapy, is no longer regarded as such since it has been found to occur with the use of other burn topical agents. Its presence is no longer an indication to discontinue silver sulfadiazine burn wound therapy. Because these side effects are uncommon, any one physician or burn facility usually has limited experience in diagnosing and treating them.

Silver sulfadiazine therapy in widespread bullous disorders: potential for toxicity.

Silver sulfadiazine (SSD) cream, most known for its use in the treatment of extensive burn wounds, is commonly used in the management of erosions in bullous disorders. The beneficial antibacterial effect of SSD use is not without risk, as silver toxicity has been well documented in burn patients. Renal insufficiency accelerates silver accumulation and thus toxicity. Data on silver toxicity in patients with primary blistering disorders is scarce; however the literature regarding silver toxicity in burn patients may be applicable to patients with bullous diseases. Hence we recommend that clinicians exercise caution when prescribing protracted wound care with SSD for blistering disorders.

Enhancing drugs absorption through third-degree burn wound eschar.

Antimicrobial therapy remains the most important method of wound infection treatment. Systemically administered antimicrobials may not achieve therapeutic levels in wound. On the other hand, some topically applied antimicrobials cannot penetrate eschar well enough. Therefore, an attempt has been made here to increase permeation of topically applied drugs through eschar using the so-called skin penetration enhancers. To perform this investigation, effects of different potential penetration enhancers on permeation of chlorhexidine, silver sulfadiazine and nitroglycerin through human third-degree burn eschar was evaluated. Results showed that water, glycerin, saline, sodium lauryl sulphate (SDS) and ethanol tend to reduce permeation of chlorhexidine through burn eschar. But, water, glycerin, hexane:ethanol and ethyl acetate:ethanol were able to increase permeation of silver sulfadiazine significantly by about 1.2-1.8 times, while saline, SDS and dimethyl sulfoxide were not able to change its permeation. Glycine showed 2.7 times enhancement toward permeation of nitroglycerin, followed by water, hexane:ethanol mixture, saline and SDS with enhancement ratios of 1.8-2.3. Urea, ethanol and citral were not able to increase permeation of nitroglycerin through eschar. This study shows that permeation of drugs through burn eschar can be improved by penetration enhancement including hydration; the effect depends on the nature of the penetrant.

A comparative study of the in vitro permeation characteristic of sulphadiazine across synthetic membranes and eschar tissue.

Infections of burn wounds are the source of significant problems in burn patients. Early excision of eschar tissue is an ideal solution to avoid sepsis. When early excision is not feasible, the application of topical antimicrobial formulations may be used to control burn wound sepsis. An understanding of the barrier properties of eschar tissue is essential for optimal design of topical antimicrobial formulations. To date, little research has been conducted on the permeability of eschar. Silver sulphadiazine (SSD) is the most frequently used topical agent in burn management. In this study, the permeation of sulphadiazine from aqueous saturated solutions of SSD through human full-thickness burn eschar tissue was studied and compared with permeability through silicone and Carbosil as model membranes. The permeation of sulphadiazine through eschar tissue was significantly higher than that through silicone and Carbosil membranes (P < 0.05). Deconvolution of the data showed that the apparent sulphadiazine diffusion coefficient was much higher in eschar tissue and was comparable to transport through an aqueous protein gel. Further studies on a greater number of compounds are suggested to elucidate the utility of such membranes as predictive models of drug permeability through eschar tissue.

Comparison of silver-coated dressing (Acticoat), chlorhexidine acetate 0.5% (Bactigrass), and silver sulfadiazine 1% (Silverdin) for topical antibacterial effect in Pseudomonas aeruginosa-contaminated, full-skin thickness burn wounds in rats.

Acticoat (Smith and Nephew, Istanbul, Turkey), chlorhexidine acetate 0.5%, and silver sulfadiazine 1% were compared to assess the antibacterial effect of their application on experimental burn wounds in contaminated with Pseudomonas aeruginosa in rats. All treatment modalities were effective against P. aeruginosa because there were significant differences between treatment groups and control groups. The mean eschar concentrations did not differ significantly between Acticoat and chlorhexidine acetate groups, but there were significant differences between the silver sulfadiazine group and the other treatment groups, indicating that silver sulfadiazine significantly eliminated P. aeruginosa more effectively in the tissues than did the other two agents. All treatment modalities were sufficient to prevent the P. aeruginosa from invading to the muscle and from causing systemic infection. In conclusion, silver sulfadiazine is the most effective agent in the treatment of the P. aeruginosa-contaminated burn wounds; Acticoat can be considered as a treatment choice because of its peculiar ability of limiting the frequency of replacing wound dressings.

How safe is silver in wound care?

Use of silver in burns, chronic ulcers and diabetic ulcers can lead to circulatory absorption and deposits in wound sites, liver, kidney and other organs. Despite this, the risks of lasting tissue damage or functional disorders are low.

Effect of topically applied silver sulfadiazine on fibroblast cell proliferation and biomechanical properties of the wound.

The effect of silver sulfadiazine (SSD) on the proliferation of human dermal fibroblast (HDF) was studied to determine the impact of the drug on the wound healing process and dermal mechanical strength. Human dermal fibroblasts were cultured to 80% confluency using DMEM with 10% FBS and viability of the cell was estimated using neutral red assay. In addition, the 2nd degree burn wound was prepared on the anterior part of rabbit ear skin and dressings containing SSD were applied for 96 h. Presence of inflammatory cells and degree of re-epithelialization were investigated in the wound. After 15 day of the induction of burn wounds, the treated area was excised and dermal mechanical strength was quantitatively measured with a constant speed tensiometer. SSD was found to be highly cyto-toxic in cultured HDF cells. The topical application of SSD (2%) could control the infection as evidenced by the lack of accumulation of inflammatory cells in histological evaluation. Therefore, these observations suggested that the impairment of dermal regeneration and decreased mechanical strength of dermal tissue was resulted from the cyto-toxic effect of SSD on dermal cells. Since the decreased mechanical strength may lead to reduction in resilience, toughness and maximum extension of the tissue, the identification of optimum dose for SSD that limits infection while minimizes the cyto-toxic effect may be clinically relevant.

Silver. 2: Toxicity in mammals and how its products aid wound repair.

The second article examining the role of this metallic element in a wound environment discusses toxicity in individual cells, animals and humans and considers how different silver-based dressings assist in wound healing.

Control of wound infections using a bilayer chitosan wound dressing with sustainable antibiotic delivery.

A novel bilayer chitosan membrane was prepared by a combined wet/dry phase inversion method and evaluated as a wound dressing. This new type of bilayer chitosan wound dressing, consisting of a dense upper layer (skin layer) and a sponge-like lower layer (sublayer), is very suitable for use as a topical delivery of silver sulfadiazine (AgSD) for the control of wound infections. Physical characterization of the bilayer wound dressing showed that it has excellent oxygen permeability, that it controls the water vapor transmission rate, and that it promotes water uptake capability. AgSD dissolved from bilayer chitosan dressings to release silver and sulfadiazine. The release of sulfadiazine from the bilayer chitosan dressing displayed a burst release on the first day and then tapered off to a much slower release. However, the release of silver from the bilayer chitosan dressing displayed a slow release profile with a sustained increase of silver concentration. The cultures of Pseudomonas aeruginosa and Staphylococcus aureus in agar plates showed effective antimicrobial activity for 1 week. In vivo antibacterial tests confirmed that this wound dressing is effective for long-term inhibition of the growth of Pseudomonas aeruginosa and Staphylococcus aureus at an infected wound site. The results in this study indicate that the AgSD-incorporated bilayer chitosan wound dressing may be a material with potential antibacterial capability for the treatment of infected wounds.

Direct evidence for uptake of intact liposomes encapsulating silver sulfadiazine by cultured human keratinocytes based on combined transmission electron microscopy and X-ray microanalysis.

Cultured human keratinocytes were exposed to liposomally encapsulated silver sulfadiazine, free silver sulfadiazine, silver sulfadiazine cream, and a corresponding vehicle for 5 min to 24 h. Phagocytosis of intact liposomes by keratinocytes was demonstrated in vitro by combined X-ray microanalysis and electron microscopy. Silver as an active part of the antimicrobial served as an electron-dense marker.

Silver aids healing in the sterile skin wound: experimental studies in the laboratory rat.

Incisional wounds 15 mm long were induced surgically in the back skin of young adult Wistar rats. They were sutured and used as an experimental model in the therapeutic evaluation of daily applications of 0.5 mL of silver nitrate (SN) at 0.01, 0.1 or 1.0% w/v aqueous solution, or 0.5 g silver sulphadiazine (SSD) over a 10-day period. Control wounds received deionized water only. The silver preparations were not toxic but SN did stain the hair and superficial layers of the stratum corneum. The wounds remained microbiologically clean. Wounds exposed to SN (0.1 or 1.0%) or SSD healed more rapidly than controls. From about the fourth day of treatment, we noted a more rapid exteriorization of sutures, improved wound closure and an earlier loss of scabs and wound debris. Silver treatment appeared to reduce the inflammatory and granulation tissue phases of healing and enhance epidermal repair. Silver from SN was deposited as silver sulphide in extrafollicular hair shafts and superficial aspects of the skin and wound debris but not at deeper levels. Silver uptake was four-fold higher in damaged skin than in intact tissue. SSD was absorbed by intact and wounded skin but the silver did not precipitate as silver sulphide and its localization in the tissue is not known. Uptake of silver from SN or SSD was associated with changes in the concentrations of zinc and calcium in the skin. Zinc levels were depressed during the inflammatory and proliferative phases of healing and then increased. Zinc concentrations had normalized by 10 days when wound healing was achieved. Calcium levels remained higher than normal throughout the observation period. The mechanism of action of silver in advancing wound healing in the rat is unclear. Its ability to reduce the inflammatory and granulation phases of healing, and to invoke metallothionein production and influence metal ion binding are possibly important.

Liposome-encapsulated silver sulfadiazine (SSD) for the topical treatment of infected burns: thermodynamics of drug encapsulation and kinetics of drug release.

Liposomes encapsulating silver sulfadiazine (SSD), the drug of choice for topical treatment of infected burns, are investigated as an improved delivery system that could act as a locally targeted sustained-release drug depot. This communication reports the first stage of the investigation and is focused on (a) the development of spectrophotometric assays for liposome-encapsulated and for free (aqueous soluble) and SSD, (b) on evaluation of the efficiency of encapsulation and kinetics of drug release. DMSO containing 140 mM NH3 was found to be the best solvent for dissolution of the liposomes and for determination of their SSD content. Peak absorption of liposome-originating SSD in this solvent is at 263 nm with em values of 23 x 10(3)-26 x 10(3). Peak absorption of SSD in aqueous solutions is at 254 nm with em magnitudes varying from 2 x 10(3) to 23 x 10(3), depending on the electrolytic composition of the system. Kinetic studies of drug release and separations by centrifugation and by gel-exclusion chromatography all indicate that the SSD in the liposomal system is distributed among three states: encapsulated, soluble unencapsulated, and stable (unencapsulated) aggregates that reside in the aqueous phase in which the liposomes are suspended. The liposomal SSD systems were found to meet the essential requirements of high-efficiency encapsulation and sustained drug release. Encapsulation efficiencies of > 80% at 10 mM lipid, reaching up to 95% at 100 mM lipid, were obtained. The release of encapsulated SSD follows first-order kinetics, with half-life up to 24 hr and with sensitivity to the electrolytes in the system. It is concluded that SSD-liposomal systems are feasible, have potential benefits over treatment with free SSD, and merit further pursuit into providing local targeting.

Sulfadiazina de prata e outros fármacos utilizados no tratamento de queimados / Silver sulfadiazine and other drugs used in burns treatment

O uso de antibactérianos tópicos tem papel decisivo no controle de infecçoes em queimaduras.A presente revisao discute vantagens e desvantagens dos fármacos disponíveis para o tratamento de queimados:nitrato de prata,iodopovidona, mafenida,acido acetico,nitrofurazona,hipoclorito de sodio,clorexidina,gentamicina,sulfadiazida de prata.Para esse último,atualmente o mais utilizado no tratamento tópico sao apresentados dados relativos ao estectro de açao,farmacocinética,reaçoes adversas e precauçoes no emprego terapêutico.