Effect of silver on burn wound infection control and healing: review of the literature

Silver compounds have been exploited for their medicinal properties for centuries. At present, silver is reemerging as a viable treatment option for infections encountered in burns, open wounds, and chronic ulcers. The gold standard in topical burn treatment is silver sulfadiazine (Ag-SD), a useful antibacterial agent for burn wound treatment. Recent findings, however, indicate that the compound delays the wound-healing process and that silver may have serious cytotoxic activity on various host cells. The present review aims at examining all available evidence about effects, often contradictory, of silver on wound infection control and on wound healing trying to determine the practical therapeutic balance between antimicrobial activity and cellular toxicity. The ultimate goal remains the choice of a product with a superior profile of infection control over host cell cytotoxicity.

Bacterial resistance to silver in wound care

Ionic silver exhibits antimicrobial activity against a broad range of micro-organisms. As a consequence, silver is included in many commercially available healthcare products. The use of silver is increasing rapidly in the field of wound care, and a wide variety of silver-containing dressings are now commonplace (e.g. Hydrofiber dressing, polyurethane foams and gauzes). However, concerns associated with the overuse of silver and the consequent emergence of bacterial resistance are being raised. The current understanding of the biochemical and molecular basis behind silver resistance has been documented since 1998. Despite the sporadic evidence of bacterial resistance to silver, there have been very few studies undertaken and documented to ascertain its prevalence. The risks of antibacterial resistance developing from the use of biocides may well have been overstated. It is proposed that hygiene should be emphasized and targeted towards those applications that have demonstrable benefits in wound care. It is the purpose of this review to assess the likelihood of widespread resistance to silver and the potential for silver to induce cross-resistance to antibiotics, in light of its increasing usage within the healthcare setting.

Silver as biocides in burn and wound dressings and bacterial resistance to silver compounds

Silver products have been used for thousands of years for their beneficial effects, often for hygiene and in more recent years as antimicrobials on wounds from burns, trauma, and diabetic ulcers. Silver sulfadiazine creams (Silvazine and Flamazine) are topical ointments that are marketed globally. In recent years, a range of wound dressings with slow-release Ag compounds have been introduced, including Acticoat, Actisorb Silver, Silverlon, and others. While these are generally accepted as useful for control of bacterial infections (and also against fungi and viruses), key issues remain, including importantly the relative efficacy of different silver products for wound and burn uses and the existence of microbes that are resistant to Ag+. These are beneficial products needing further study, although each has drawbacks. The genes (and proteins) involved in bacterial resistance to Ag have been defined and studied in recent years.

Photo-Inspired Antibacterial Activity and Wound Healing Acceleration by Hydrogel Embedded with Ag/Ag@AgCl/ZnO Nanostructures

Ag/Ag@AgCl/ZnO hybrid nanostructures are embedded in a hydrogel by a simple two-step technique. The Ag/Ag@AgCl nanostructures are assembled in the hydrogel via ultraviolet light chemical reduction followed by incorporation of ZnO nanostructures by NaOH precipitation. The hydrogel accelerates wound healing and exhibits high antibacterial efficiency against both Escherichia coli and Staphylococcus aureus under visible light irradiation. The Ag/Ag@AgCl nanostructures enhance the photocatalytic and antibacterial activity of ZnO due to the enhancement of reactive oxygen species by visible light. This hydrogel system kills 95.95% of E. coli and 98.49% of S. aureus within 20 min upon exposure to simulated visible light, and rapid sterilization plays a crucial role in wound healing. In addition, this system provides controllable, sustained release of silver and zinc ions over a period of 21 days arising from the reversible swelling-shrinking transition of the hydrogel triggered by the changing pH value in the biological environment. About 90% Zn²⁺ release is observed in the acidic environment after 3 days, whereas only 10% Zn²⁺ release occurs in the neutral environment after 21 days. In vivo results show that release of Ag⁺ and Zn²⁺ stimulates the immune function to produce a large number of white blood cells and neutrophils (2-4 times more than the control), thereby producing the synergistic antibacterial effects and accelerated wound healing.

Silver. I: Its antibacterial properties and mechanism of action

Silver products have two key advantages: they are broad-spectrum antibiotics and are not yet associated with drug resistance. This article, the first in a two-part series, describes the main mechanism of action of this metallic element.

Extending the TIME concept: what have we learned in the past 10 years?(*)

The TIME acronym (tissue, infection/inflammation, moisture balance and edge of wound) was first developed more than 10 years ago, by an international group of wound healing experts, to provide a framework for a structured approach to wound bed preparation; a basis for optimising the management of open chronic wounds healing by secondary intention. However, it should be recognised that the TIME principles are only a part of the systematic and holistic evaluation of each patient at every wound assessment. This review, prepared by the International Wound Infection Institute, examines how new data and evidence generated in the intervening decade affects the original concepts of TIME, and how it is translated into current best practice. Four developments stand out: recognition of the importance of biofilms (and the need for a simple diagnostic), use of negative pressure wound therapy (NPWT), evolution of topical antiseptic therapy as dressings and for wound lavage (notably, silver and polyhexamethylene biguanide) and expanded insight of the role of molecular biological processes in chronic wounds (with emerging diagnostics and theranostics). Tissue: a major advance has been the recognition of the value of repetitive and maintenance debridement and wound cleansing, both in time-honoured and novel methods (notably using NPWT and hydrosurgery). Infection/inflammation: clinical recognition of infection (and non infective causes of persisting inflammation) is critical. The concept of a bacterial continuum through contamination, colonisation and infection is now widely accepted, together with the understanding of biofilm presence. There has been a return to topical antiseptics to control bioburden in wounds, emphasised by the awareness of increasing antibiotic resistance. Moisture: the relevance of excessive or insufficient wound exudate and its molecular components has led to the development and use of a wide range of dressings to regulate moisture balance, and to protect peri-wound skin, and optimise healing. Edge of wound: several treatment modalities are being investigated and introduced to improve epithelial advancement, which can be regarded as the clearest sign of wound healing. The TIME principle remains relevant 10 years on, with continuing important developments that incorporate new evidence for wound care.

A large randomized clinical trial of a silver-impregnated urinary catheter: lack of efficacy and staphylococcal superinfection

PURPOSE

The antibacterial activity of silver-containing compounds has recently been employed in constructing medical devices, such as vascular and urinary catheters, that may be effective in blocking infection. The present study was designed to evaluate the efficacy of a silver oxide-coated urinary catheter.

PATIENTS AND METHODS

A total of 1,309 hospitalized patients who required placement of an indwelling urinary catheter for 24 hours or longer were randomly assigned to receive either a silicone catheter coated externally with 5% silver oxide or a standard silicone elastomer-coated latex catheter. Daily catheter-urine specimens were collected aseptically and catheter-care violations were monitored daily for the duration of the catheterization.

RESULTS

Bacteriuria developed in 85 of 745 patients (11.4%) in the silver-coated catheter group and in 73 of 564 patients (12.9%) in the control group (P = 0.45). In women who did not receive antibiotics, the rates were 29.3% and 30.4%, respectively (P = 0.98). In men who did not receive antibiotics, the rate of bacteriuria was significantly higher with the silver-coated catheter (29.4% compared to 8.3%, respectively, P = 0.02). Staphylococcal species were isolated more often from the silver-coated catheter group than from the control group (25% versus 8% of all isolates, respectively, P = 0.002).

CONCLUSIONS

This study, the largest ever reported evaluating any silver-impregnated device, has not only failed to demonstrate the efficacy of silver in prevention of catheter-associated bacteriuria, as suggested in prior studies, but it has also shown a significantly increased incidence of bacteriuria in male patients and a significantly increased occurrence of staphylococcal bacteriuria. These results suggest the need for caution and for similar large-scale trials before silver-containing compounds are widely used for preventing device-associated infections, both in vascular and urinary catheters.

Silver products for medical indications: risk-benefit assessment

BACKGROUND

Legitimate medicinal use of silver-containing products has dramatically diminished over the last several decades. Recently, however, some manufacturers have begun to enthusiastically promote oral colloidal silver proteins as mineral supplements and for prevention and treatment of many diseases. Indiscriminate use of silver products can lead to toxicity such as argyria.

OBJECTIVE

To assist health care professionals in a risk versus benefit assessment of over-the-counter silver-containing products, we herein examine the following issues: historical uses, chemistry, pharmacology, clinical toxicology, case reports of adverse events in the literature, and the recent promotion of over-the-counter silver products. Other sources of silver exposure (including environmental and dietary) and EPA exposure standards are discussed. A list of currently available silver products is provided for easy reference and screening.

CONCLUSIONS

We emphasize the lack of established effectiveness and potential toxicity of these products.

A new "silver-bullet" to treat caries in children--nano silver fluoride: a randomised clinical trial

BACKGROUND

Untreated dental caries in children remains a public health challenge in poor communities.

OBJECTIVES

This prospective controlled clinical trial investigated the effectiveness of a new anti-caries agent, Nano Silver Fluoride (NSF), applied once a year to arrest caries in children.

METHODS

One hundred thirty decayed primary teeth were randomly divided into two groups: NSF as the experimental agent and water as the control group. Teeth were clinically diagnosed and treated by one masked examiner and followed up at seven days and five and 12 months by another calibrated examiner who was blinded to the type of treatment. The criteria of the ICDAS II were followed to determine the activity of lesion and the diagnosis of caries. The Pearson's chi-square test was used to compare the groups during different follow-up exams.

RESULTS

At seven days, 81% of teeth in the NSF group exhibited arrested caries, whereas in controls, no teeth had arrested decay (p<0.001) [PF, prevented fraction=81%]. After five months, the NSF group had 72.7% with arrested decay, and the control group had 27.4% (p<0.001) [PF=62.5%]. At 12 months, 66.7% of the lesions treated with NSF were still arrested, while the control group had 34.7% remaining arrested (p=0.003) [PF=50%]. The number need to treat (NNT) at five months was two, and at 12 months, the number was three.

CLINICAL SIGNIFICANCE

The NSF formulation is effective to arrest active dentine caries and not stain teeth.

CONCLUSIONS

NSF was demonstrated to be effective in arresting caries in children in poor communities.

Increased Bacterial Burden and Infection

PURPOSE

The purpose of this article is to provide practitioners with an overview of wound infection/inflammation and bacterial balance and to offer a guide to assessment and treatment of chronic wounds.

TARGET AUDIENCE

This continuing education activity is intended for physicians and nurses who assess and treat wound infections.

OBJECTIVES

After reading this article and taking this test, the participant should be able to: 1. Discuss factors associated with infection of the chronic wound, including the concept of bacterial balance and burden. 2. Identify signs of infection in the chronic wound and applicable diagnostic tests. 3. Describe appropriate treatment for the infected chronic wound.

Topical silver for treating infected wounds

BACKGROUND

Topical silver treatments and silver dressings are increasingly used for the local treatment of contaminated or infected wounds, however, there is a lack of clarity regarding the evidence for their effectiveness.

OBJECTIVES

To evaluate the effects on wound healing of topical silver and silver dressings in the treatment of contaminated and infected acute or chronic wounds.

SEARCH STRATEGY

We sought relevant trials from the Cochrane Central Register of Controlled Trials (CENTRAL), the Cochrane Wounds Group Specialised Register in March 2006 and in MEDLINE, EMBASE, CINAHL, and digital dissertations databases up to September 2006. In addition, we contacted companies, manufacturers and distributors for information to identify relevant trials.

SELECTION CRITERIA

Randomised controlled trials (RCTs) assessing the effectiveness of topical silver in the treatment of contaminated and infected acute or chronic wounds.

DATA COLLECTION AND ANALYSIS

Eligibility of trials, assessment of trial quality and data extraction were undertaken by two authors independently. Disagreements were referred to a third author.

MAIN RESULTS

Three RCTs were identified, comprising a total of 847 participants. One trial compared silver-containing foam (Contreet) with hydrocellular foam (Allevyn) in patients with leg ulcers. The second trial compared a silver-containing alginate (Silvercel) with an alginate alone (Algosteril). The third trial compared a silver-containing foam dressing (Contreet)) with best local practice in patients with chronic wounds.The data from these trials show that silver-containing foam dressings did not significantly increase complete ulcer healing as compared with standard foam dressings or best local practice after up to four weeks of follow-up, although a greater reduction of ulcer size was observed with the silver-containing foam. The use of antibiotics was assessed in two trials, but no significant differences were found. Data on pain, patient satisfaction, length of hospital stay, and costs were limited and showed no differences. Leakage occurred significantly less frequently in patients with leg ulcers and chronic wounds treated with a silver dressing than with a standard foam dressing or best local practice in one trial.

AUTHORS' CONCLUSIONS

Only three trials with a short follow-up duration were found. There is insufficient evidence to recommend the use of silver-containing dressings or topical agents for treatment of infected or contaminated chronic wounds.

Evidence-Based Dentistry Update on Silver Diamine Fluoride

This article reviews current evidence on the effectiveness of silver diamine fluoride (SDF) as a caries arresting and preventive agent. It provides clinical recommendations around SDF's appropriate use as part of a comprehensive caries management program. Systematic reviews confirm that SDF is effective for caries arrest on cavitated lesions in primary teeth and root caries in the elderly. It may also prevent new lesions. Application is easy, noninvasive, affordable, and safe. Although it stains the lesions dark as it arrests them, it provides clinicians with an additional tool for caries management when esthetics are not a primary concern.

Prospective randomized controlled study of Hydrofiber dressing containing ionic silver or calcium alginate dressings in non-ischaemic diabetic foot ulcers

AIMS

Diabetic foot ulcers (DFUs) are at risk of infection and impaired healing, placing patients at risk of lower extremity amputation. DFU care requires debridement and dressings. A prospective, multicentre study compared clinical efficacy and safety of AQUACEL Hydrofiber dressings containing ionic silver (AQAg) with those of Algosteril calcium alginate (CA) dressings in managing out-patients with Type 1 or 2 diabetes mellitus and non-ischaemic Wagner Grade 1 or 2 DFUs.

METHODS

Patients stratified by antibiotic use on enrolment were randomly assigned to similar protocols including off-loading, AQAg (n = 67) or CA (n = 67) primary dressings and secondary foam dressings for 8 weeks or until healing. Clinical efficacy measures were healing outcomes and primarily healing speed. Adverse events were recorded.

RESULTS

AQAg and CA groups were comparable at baseline. All ulcer healing outcomes improved in both groups. The mean time to healing was 53 days for AQAg ulcers and 58 days for CA ulcers (P = 0.34). AQAg-treated ulcers reduced in depth nearly twice as much as CA-treated ulcers (0.25 cm vs. 0.13 cm; P = 0.04). There was more overall ulcer improvement and less deterioration in AQAg subjects (P = 0.058), particularly in the subset initially using antibiotics (P = 0.02). Safety profiles of both groups were similar.

CONCLUSION

When added to standard care with appropriate off-loading, AQAg silver dressings were associated with favourable clinical outcomes compared with CA dressings, specifically in ulcer depth reduction and in infected ulcers requiring antibiotic treatment. This study reports the first significant clinical effects of a primary wound dressing containing silver on DFU healing.

Topical silver for preventing wound infection

BACKGROUND

Silver-containing treatments are popular and used in wound treatments to combat a broad spectrum of pathogens, but evidence of their effectiveness in preventing wound infection or promoting healing is lacking.

OBJECTIVES

To establish the effects of silver-containing wound dressings and topical agents in preventing wound infection and healing of wounds.

SEARCH STRATEGY

We searched the Cochrane Wounds Group Specialised Register (6 May 2009); The Cochrane Central Register of Controlled Trials (CENTRAL) (2009 Issue 2); Ovid MEDLINE (1950 to April Week 4 2009); Ovid EMBASE (1980 to 2009 Week 18); EBSCO CINAHL (1982 to April Week 4 2009) and Digital Dissertations (to May 2009) for relevant trials. We contacted manufacturers and distributors.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing silver-containing wound dressings and topical agents with silver-containing and non silver-containing comparators on uninfected wounds.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials, assessed risk of bias, and extracted data.

MAIN RESULTS

We identified 26 RCTs (2066 patients). Heterogeneity of treatments and outcomes precluded meta-analysis. We grouped results according to wound type, and silver preparation.BurnsThirteen trials compared topical silver (in a variety of formulations - including silver sulphadiazine (SSD) cream) with non-silver dressings. One trial showed fewer infections with silver nitrate when compared with a non-silver dressing, but three trials showed significantly more infection with SSD than with the non-silver dressing.Six trials compared SSD cream with silver-containing dressings. One showed significantly fewer infections with the silver-containing dressing (Hydron AgSD) compared with SSD, the remaining five found no evidence of a difference.One trial compared two silver-containing dressings, and showed a significantly lower infection rate with silver-coated gauze (Acticoat(R)) than with silver nitrate gauze.Other woundsSix trials compared SSD/silver-containing dressings with non-silver dressings (nine dressings in total). Most comparisons (seven) found no significant differences in infection rates; one trial in a variety of wounds exhibited significantly fewer infections with SSD/hydrocolloid, but another, in acute wounds, found significantly more infections with SSD. Only one comparison showed a significant reduction in healing time associated with a silver-containing hydrofibre dressing in diabetic foot ulcers.

AUTHORS' CONCLUSIONS

There is insufficient evidence to establish whether silver-containing dressings or topical agents promote wound healing or prevent wound infection; some poor quality evidence for SSD suggests the opposite.

Effect of a sustained silver-releasing dressing on ulcers with delayed healing: the CONTOP study

OBJECTIVE

To compare the effect of the sustained silver-releasing foam dressing Contreet Foam (ColoplastA/S) with local best practice (LBP) on delayed healing ulcers using a real-life setting.

METHOD

A total of 619 patients with ulcers of varying aetiologies were treated for four weeks with either the silver foam dressing or LBP.

RESULTS

Wound area was reduced by 50% with the silver foam and 34% with LBP Less slough and maceration, a faster reduction in exudate level and more positive wound progress was achieved with the silver foam. In addition, exudate handling, ease of use, odour and pain improved. Less time was spent on dressing changes, and mean wear time was longer for the silver foam (3.1 days) than for LBP (2.1 days). All differences were statistically significant (p < 0.05). The silver foam dressing outperformed all of the other dressing categories including moist wound healing products and other silver dressings.

CONCLUSION

This large-scale comparative real-life study shows that the silver foam dressing supports faster healing of delayed healing wounds.

The Effect of Silver Diamine Fluoride in Preventing Caries in the Primary Dentition: A Systematic Review and Meta-Analysis

OBJECTIVES

To investigate whether silver diamine fluoride (SDF) is effective in preventing new caries lesions in primary teeth when compared to placebo or active treatments.

METHODS

Systematic review (CRD42016036963) of controlled clinical trials. Searches were performed in 9 electronic databases, 5 registers of ongoing trials, and reference lists of identified review articles. Two researchers carried out data extraction and quality appraisal independently. The primary outcome was the difference in caries increment (decayed, missing, and filled surfaces or teeth - dmfs or dmft) between SDF and control groups. These differences were pooled as weighted mean differences (WMD) and prevented fractions (PF).

RESULTS

Searches yielded 2,366 unique records; 6 reports of 4 trials that randomized 1,118 and analyzed 915 participants were included. Two trials compared SDF to no treatment, 1 compared SDF to placebo and sodium fluoride varnish (FV), and 1 compared SDF to high-viscosity glass ionomer cement (GIC). All studies had at least 1 domain with unclear or high risk of bias. After 24 months of follow-up, in comparison to placebo, no treatment, and FV, SDF applications significantly reduced the development of new dentin caries lesions (placebo or no treatment: WMD = -1.15, PF = 77.5%; FV: WMD = -0.43, PF = 54.0%). GIC was more effective than SDF after 12 months of follow-up but the difference between them was not statistically significant (WMD, dmft: 0.34, PF: -6.09%).

CONCLUSION

When applied to caries lesions in primary teeth, SDF compared to no treatment, placebo or FV appears to effectively prevent dental caries in the entire dentition. However, trials specifically designed to assess this outcome are needed.

The silver-releasing foam dressing, Contreet Foam, promotes faster healing of critically colonised venous leg ulcers: a randomised, controlled trial

The study compared the effect of a sustained silver-release foam dressing (Contreet Foam) with a foam dressing (Allevyn Hydrocellular) without added silver in critically colonised venous leg ulcers with delayed healing. The study was a multicentre, open, randomised, controlled study lasting for 4 weeks. Ulcer area and healing were assessed weekly. Odour, maceration, absorption capacity and leakage were evaluated at dressing changes. All adverse events were recorded. One hundred and twenty-nine patients were included (Contreet Foam: 65, Allevyn Hydrocellular: 64). The two groups were comparable in all respects. After 4 weeks, there was a significantly greater reduction in ulcer area in the Contreet Foam group (45%) than in the Allevyn Hydrocellular group (25%). After 1 and 4 weeks, odour was present in significantly less of the ulcers in the Contreet Foam group (17% and 19%, respectively) compared with the Allevyn Hydrocellular group (47% and 39%, respectively) and at the final visit there were significantly fewer leakages in the Contreet Foam group (19%) compared with the Allevyn Hydrocellular group (49%). Also, less maceration was observed after 1 and 4 weeks in the Contreet Foam group (34% and 37%, respectively) compared with the Allevyn Hydrocellular group (55% and 48%, respectively). The occurrence and cause of adverse events were equally distributed between the study groups. The present study provides evidence of the superior performance of the silver-releasing dressing, Contreet Foam, compared with a traditional moist foam wound healing dressing in the treatment of critically colonised, chronic venous leg ulcers. The results of this randomised, controlled study suggest an important role of sustained silver-releasing dressings in the treatment of critically colonised chronic wounds.

Anomaly and correlation of killing in the therapeutic properties of silver (I) chelation with glutamic and tartaric acids

OBJECTIVES

To investigate whether silver chelates or silver ions are more effective as therapeutic agents, and to examine their mode of action so that safer and stable compounds that have a broad spectrum of therapeutic activities can be developed.

METHODS

Efficacy was investigated against Pseudomonas aeruginosa (ATCC 15442) by determining MIC via a broth macrodilution procedure using NCCLS methods for antibiotic susceptibility testing.

RESULTS

It was found that the responsible agent for silver therapeutic properties is the silver chelates rather than silver ions, contradicting previous findings, and the efficacy profiles mimic that of free silver ions present in solution.

CONCLUSIONS

Silver therapeutic activities seem to be more effective as complexes-an intracellular package-rather than free silver ions, demonstrating that the effect of silver is linked to cells' DNA unwinding, and not respiratory or membrane functionality as was traditionally recognized.

Scintillator-Based Nanohybrids with Sacrificial Electron Prodrug for Enhanced X-ray-Induced Photodynamic Therapy

X-ray-induced photodynamic therapy (X-PDT) has high depth of penetration and has considerable potential for applications in cancer therapy. Scintillators and heavy metals have been adopted to absorb X-rays and transmit the energy to photosensitizers. However, the low efficiency of converting X-rays to reactive oxygen species (ROS) presents a challenge for the use of X-PDT to cure cancer. In this study, a new method based on LiLuF₄:Ce@SiO₂@Ag₃PO₄@Pt(IV) nanoparticles (LAPNP) is presented that could be used to enhance the curative effects of X-PDT. To make full use of the fluorescence produced by nanoscintillators (LiLuF₄:Ce), a cisplatin prodrug Pt(IV) was utilized as a sacrificial electron acceptor to increase the yield of hydroxyl radicals (·OH) by increasing the separation of electrons and holes in photosensitizers (Ag₃PO₄). Additionally, cisplatin is produced upon the acceptance of electrons by Pt(IV) and further enhances the damage caused by ·OH. Via two-step amplification, the potential of LAPNP to enhance the effects of X-PDT has been demonstrated.

Synthesis, X-ray crystal structure, anti-fungal and anti-cancer activity of [Ag2(NH3)2(salH)2] (salH2=salicylic acid)

[Ag(2)(NH(3))(2)(salH)(2)] (salH(2)=salicylic acid) was synthesised from salicylic acid and Ag(2)O in concentrated aqueous NH(3) and the dimeric Ag(I) complex was characterised using X-ray crystallography. The complex is centrosymmetric with each metal coordinated to a salicylate carboxylate oxygen and to an ammonia nitrogen atom in an almost linear fashion. The two [Ag(NH(3))(salH)] units in the complex are linked by an Ag-Ag bond. Whilst metal-free salH(2) did not prevent the growth of the fungal pathogen Candida albicans [Ag(2)(NH(3))(2)(salH)(2)], [Ag(2)(salH)(2)] and some simple Ag(I) salts greatly inhibited cell reproduction. SalH(2), [Ag(2)(NH(3))(2)(salH)(2)] [Ag(2)(salH)(2)] and AgClO(4) produced a dose-dependent cytotoxic response against the three human derived cancer cell lines, Cal-27, Hep-G2 and A-498, with the Ag(I)-containing reagents being the most effective.

Biomedical Potential of Ultrafine Ag/AgCl Nanoparticles Coated on Graphene with Special Reference to Antimicrobial Performances and Burn Wound Healing

In recent years, researchers have proven the release of silver ions (Ag(+)) from silver nanoparticles (Ag NPs) significantly affects their toxicity to bacteria and other organisms. Due to the difficulty in maintaining a steady flux of a high concentration of Ag(+), it is still challenging to develop a highly efficient, stable, and biocompatible Ag NP-based antimicrobial material. To circumvent this issue, we developed a new Ag-based bactericide through the fabrication of sunlight-driven and ultrafine silver/silver chloride anchored on reduced graphene oxide (Ag/AgCl/rGO). This stable Ag/AgCl nanophotocatalyst with negligible release of Ag(+) generated a high amount of oxidative radicals, killing the bacteria, thus achieving both high bactericidal efficiency and stability. Moreover, functionalization of the nanomaterial with poly(diallyldimethylammonium chloride) (PDDA) gives it a highly adsorptive capacity, which allows it to capture the bacteria and possibly enhances the bactericidal activity. In vivo histopathological studies showed that the Ag/AgCl/rGO nanomaterial could obviously promote the regeneration of the epidermis, which indicated the good biomedical potential of Ag/AgCl/rGO nanomaterial in burn wound healing.

A prospective randomised open label study to evaluate the potential of a new silver alginate/carboxymethylcellulose antimicrobial wound dressing to promote wound healing

The aim of this study was to observe both the clinical signs and symptoms of wounds at risk of infection, that is critically colonised (biofilm infected) and antimicrobial-performance of an ionic silver alginate/carboxymethylcellulose (SACMC) dressing, in comparison with a non silver calcium alginate fibre (AF) dressing, on chronic venous leg and pressure ulcers. Thirty-six patients with venous or pressure ulcers, considered clinically to be critically colonised (biofilm infected), were randomly chosen to receive either an SACMC dressing or a non silver calcium AF dressing. The efficacy of each wound dressing was evaluated over a 4-week period. The primary study endpoints were prevention of infection and progression to wound healing. The SACMC group showed a statistically significant (P = 0.017) improvement to healing as indicated by a reduction in the surface area of the wound, over the 4-week study period, compared with AF controls. In conclusion, the SACMC dressing showed a greater ability to prevent wounds progressing to infection when compared with the AF control dressing. In addition, the results of this study also showed an improvement in wound healing for SACMC when compared with a non silver dressing.

Clinical performance of a new silver dressing, Contreet Foam, for chronic exuding venous leg ulcers

OBJECTIVE

This study aimed to evaluate the safety and performance of a new sustained silver-releasing dressing, Contreet Foam (Coloplast A/S), in the treatment of moderately to highly exuding chronic venous leg ulcers in which healing is delayed due to the presence of bacteria.

METHOD

The clinical performance of Contreet Foam was studied for four weeks in 25 patients with moderately to highly exuding delayed-healing venous leg ulcers. Healing was assessed on a weekly basis with reference to the wound-bed tissue composition, degree of odour and pain, dressing performance and the dressing's effect on the peri-ulcer area. Blood samples were analysed for silver content.

RESULTS

Twenty-three out of 25 patients completed the study. One ulcer healed and no wound infections occurred during the study period. A mean 56% reduction in ulcer area (from 15.6 to 6.9 cm2) was recorded during the four weeks, and there was a mean 25% reduction in granulation tissue from dull to healthy after one week. Wound odour reduced significantly after one week. Mean dressing wear time was 3.1 days, and there were only minimal incidences of leakage. Serum silver levels did not exceed reference values.

CONCLUSION

Contreet Foam was found to be safe and performed well when used in the treatment of delayed-healing chronic venous leg ulcers, combining effective antibacterial properties with excellent exudate management.

DECLARATION OF INTEREST

This study was supported by Coloplast A/S, Humlebaek, Denmark.

Healing of porcine donor sites covered with silver-coated dressings

OBJECTIVE

To compare rates of healing of donor sites in pigs between those dressed with silver-coated dressings and those dressed with petrolatum-impregnated absorbent gauze.

DESIGN

Open study with each animal acting as its own control.

SETTING

University research facility, Canada.

ANIMALS

6 young specific-pathogen-free domestic pigs.

INTERVENTIONS

A total of 72 wounds about 1 cm x 2 cm x 0.4 mm were made in rows of eight on each pig with a dermatome. They were divided into three groups of 24, and dressed with petrolatum gauze, or silver-coated dressings moistened with sterile water either once only or daily for 10 days. All dressings were secured in place with an elastic bandage.

MAIN OUTCOME MEASURES

Erythema, infection, epidermal migration, and healing.

RESULTS

Wounds dressed with moistened silver-coated dressings re-epithelialised significantly more quickly. This resulted in complete re-epithelialisation within 70% of the time taken by those wounds dressed with petrolatum gauze.

CONCLUSION

Silver-coated dressings provide a moist environment for the healing wound combined with an effective antimicrobial agent, and this significantly accelerates healing compared with wounds dressed with traditional petrolatum gauze dressings.