Unique Chemical Structure and Clinical Efficacy of Ag Oxysalts

Transcription

1 This publication is a supplement to December 2018 fresh views on silver Unique Chemical Structure and Clinical Efficacy of Ag Oxysalts Sonya Dick, PT, DPT, CWS, FACCWS Clinical Resource Manager, Crawford Healthcare University of Kentucky, College of Medicine, Lexington, KY Lindsay Kalan, PhD Assistant Professor, University of Wisconsin-Madison, Madison, WI Helen A. Thomason, PhD Head of Scientific Research, Crawford Healthcare University of Manchester, Knutsford, UK Poonam Joshi, MD, CWS-P Medical Director of the Amita Alexian Wound Care Center, Greater Chicago, IL This publication was not subject to the OWM peer-review process.

2 Introduction Chronic wounds affect large numbers of patients globally and produce a substantial socioeconomic burden. Cost containment relies on timely healing of wounds and management of infection. Appropriate treatment of chronic wounds to promote timely healing is therefore a key focus for clinicians treating wounds. Antimicrobial silver dressings are used in the management of wound infections. The formulation of silver used in these dressings will influence antimicrobial activity and clinical effectiveness. So, clearly, clinicians must have a thorough understanding of the properties of a product to ensure effective use. Ag Oxysalts (silver oxynitrate) is a silver compound with unique properties that produce rapid, sustained, broad-spectrum antimicrobial activity. Ag Oxysalts is currently the only silver compound used in dressings to release Ag1+, Ag2+, and Ag3+ ions. This supplement to Ostomy Wound Management was developed for the following objectives: Discuss how the chemical properties of Ag Oxysalts relate to its antimicrobial activity and clinical performance Describe how Ag Oxysalts effect the wound environment and promote healing independent of infection Explore the potential impact of Ag Oxysalts dressings such as KerraCel Ag (Crawford Healthcare) on wound healing through the presentation of clinical cases Understand how a Healthcare Professional (HCP) might explore the cytotoxicity, bacterial resistance, and biofilm disruption claims of the Ag Oxysalts technology A Scientific Perspective Luna, argentum, silver (Ag). As a metal of antiquity, the initial discovery of Ag is lost to history, but in the 21st century, its uses continue to evolve. Dr. Kalan was first introduced to Ag as she was immersed in research on the creation of new antibiotics that target drug-resistant microbes. She was asked to evaluate Ag Oxysalts, a unique silver compound (Ag 7 NO 11 ) and approached this as a scientist would with a small molecule antibiotic, beginning with the question: How does chemistry influence antimicrobial efficacy? Ag is mined from the earth as pure metallic Ag 0 (s) or the salt AgCl(s), neither of which has antimicrobial activity. This is because the soluble Ag ion (Ag 1+ ) is required to capture electrons from bacterial cells, allowing Ag to be reduced back to a stable form (Ag 0 ). 1,2 Electrons are like currency within a bacterial cell. They enable the cell to generate the energy required for DNA replication, protein synthesis, and cell division. If electron transfer processes are disrupted, the cell cannot survive. Ag Oxysalts are different from other Ag compounds in many ways; this summary will focus on solubility and a higher reduction potential. Where do soluble Ag ions come from? A salt is an ionic complex composed of equal numbers of positively and negatively charged ions. Ag can exist as different salt compounds such as silver chloride (AgCl), silver sulfate (Ag 2 SO 4 ), or silver oxynitrate (Ag 7 NO 11 ). The formulation of Ag salts can greatly influence stability, solubility, and subsequent antimicrobial activity. 3,4 Some compounds such as AgCl are virtually insoluble (remember this stable compound represents a major source of mined silver). Other silver compounds, including Ag Oxysalts, are less stable and have high solubility in fluid, quickly releasing Ag ions to exert their activity. This is the Figure 1. Ability to acquire electrons. Ag Oxysalts has 3 missing electrons, allowing it pull more electrons from bacteria to disrupt their function faster. 2

3 Table 1. Standard Reduction Potentials Reaction Reduction Potential (V) Ag 3+ + e Ag Ag 2+ + e Ag Ag 2 O + 2H + + 2e 2Ag 0 + 2H 2 O Ag+ + e Ag Ag 2 SO 4 + 2e 2Ag + SO Ag 2 O + H 2 O + 2e 2Ag 0 + 2OH AgCl + e Ag 0 + Cl case when oxygen is the anion used to stabilize positively charged Ag ions. Oxygen also is able to complex and stabilize more reactive Ag ions that exist in a higher oxidation state. This is a property that sets Ag Oxysalts apart from other Ag salts. Oxygen molecules stabilize the high reduction potential Ag 2+ and Ag 3+ ions, releasing oxygen alongside these highly reactive Ag ions when in contact with fluid. 5-9 What does a higher reduction potential mean? Reduction potential measures the ability to acquire electrons. The higher the reduction potential, the stronger the affinity for capturing electrons. To put it simply, Ag 2+ and Ag 3+ are stronger than Ag +, allowing these ions to pull more electrons from different metabolic reactions and processes within a microbial cell (Figure 1). For example, Ag 3+ has a reduction potential of +1.80V compared to the +0.8V for Ag + (Table 1), 10 and it needs to gain three electrons to get back to its stable state of Ag 0 compared to only one electron for Ag +. Speaking strictly about chemistry, solubility and reduction potential are two properties that influence antimicrobial activity. Compared side-by-side, Ag Oxysalts have the lowest minimum inhibitory concentration and minimum biofilm eradication concentration compared to other ionic Ag salts, resulting in less overall Ag use but greater efficacy. 3,4 Clinically speaking, a highly soluble compound allows for bacteria to be killed faster. A higher reduction potential leads to higher efficacy. When you combine a highly soluble compound with high reduction potential, you have a compound that has the speed and strength to kill bacteria within a biofilm without cytotoxicity. Other properties and the effects of Ag Oxysalts on the wound environment are also currently being studied. Inflammation is a crucial part of wound healing. When a wound occurs, neutrophils and macrophage are recruited to the site to remove pathogens, foreign material, and devitalized tissue. Once the wound is cleared of these substances, inflammatory cell levels diminish until healing is complete. However, in chronic wounds inflammation is heightened and prolonged. Increased numbers of neutrophils and macrophage persist within the wound. These inflammatory cells Figure 2. Ag Oxysalts promote many aspects of wound repair. The potent antimicrobial efficacy of Ag Oxysalts effectively kills bacteria within a wound biofilm. Despite the powerful antimicrobial action, dressings containing Ag Oxysalts promote healing of uninfected mouse wounds, reducing wound area, promoting reepithelialization, and dampening inflammation. The unique ability of dressings containing Ag Oxysalts to directly generate oxygen and to catalyze the breakdown of hydrogen peroxide to oxygen and water may be sufficient to create a more favorable wound environment to stimulate healing. 3

4 secrete a cocktail of proteinases, proinflammatory cytokines, and reactive oxygen species (ROS), including superoxide anions (O 2. - ) and hydrogen peroxide (H 2 O 2 ), that sustain inflammation and cause tissue damage. In turn, tissue damage supports microbial growth; consequently, infection is a frequent complication associated with chronic wounds. In an attempt to clear infection, additional inflammatory cells are recruited to the wound, leading to a cycle of elevated inflammation and causing tissue damage that supports microbial growth which, in turn, increases inflammation, exacerbating the hostile wound environment and inability to heal. A wound stuck in the inflammatory stage of repair depletes the tissue of vital oxygen, an essential element in the generation of energy. During healing, demand for energy and subsequently oxygen to generate this energy are increased. Inflammatory cells consume high levels of "Despite their potent antimicrobial efficacy, Ag Oxysalts do not adversely affect healing independent of infection. On the contrary, Ag Oxysalts promoted many aspects of wound repair when infection is not present." oxygen; during phagocytosis, these cells utilize oxygen in the production of superoxide ions and hydrogen peroxide. 11 Infection exacerbates the problem, because aerobic bacteria consume oxygen within the wound. Thus, stalled or infected wounds often are deprived of vital oxygen. Therefore, antimicrobial therapies are paramount in the fight against wound infection when the host immune response is failing. These antimicrobial therapies need to be powerful enough to combat recalcitrant processes such as the development of biofilms that show increased tolerance to the host immune response and antimicrobial therapies. However, the potent nature of the antimicrobial therapies must not adversely affect the wound environment. Dressings containing Ag Oxysalts exhibit superior antimicrobial activity against both planktonic and biofilm-embedded microbes as compared to traditional silver dressings. 3,4 Silvers have a long-standing history in the management of wound infections; however, concerns have been raised over their cytotoxicity and the effects they have on healing when infection is not present. Recently, the effects of Ag Oxysalts on healing independent of infection were assessed. 12 Ag Oxysalts were added to the culture media of fibroblast and keratinocyte scratch wound assays. No effect was observed on the closure of fibroblast scratch wounds with the addition of Ag Oxysalts ; however, keratinocyte scratch wounds treated with Ag Oxysalts healed faster. When Ag Oxysalt dressings were applied to uninfected mouse wounds, the wounds healed faster, showing a reduction in wound area, increased reepithelialization, and decreased inflammation. 12 An examination was conducted of how Ag Oxysalts promote healing when infection is not present. Ag Oxysalts exposed to fluid are thought to break down and generate oxygen. These silver compounds were added to serum and the level of oxygen within the serum measured. Of the silver compounds tested, only Ag Oxysalts generated oxygen. In the wound environment, this oxygen may provide vital energy to the numerous cell types that require additional energy for effective repair. In a chronic wound, the addition of oxygen directly to the wound tissue may be sufficient to shift the wound out of a nonhealing state. Ag Oxysalts also may promote healing through the ability to breakdown H 2 O 2. Silver is a known catalyst of H 2 O 2, breaking it down into oxygen and water. H 2 O 2, produced by neutrophils and macrophage, is the primary mechanism for killing bacteria; however, this process causes severe tissue damage. During normal wound healing, enzymes rapidly detoxify H 2 O In chronic and infected wounds, levels can become unregulated. The ability of a variety of silver dressings to catalyse the breakdown of H 2 O 2 was assessed. Only dressings containing Ag Oxysalts were able to catalyze the breakdown of H 2 O 2 to oxygen and water. In recent years, the regulation of ROS through antioxidants and antioxidative enzymes has been examined as a mechanism to reduce oxidative stress-induced tissue damage and promote healing. 14 The ability of Ag Oxysalts to breakdown H 2 O 2 may rebalance redox signalling and create a less hostile wound environment to support repair. These recent studies have shed light on the mechanisms of action of Ag Oxysalts. Despite their potent antimicrobial efficacy, Ag Oxysalts do not adversely affect healing independent of infection. On the contrary, Ag Oxysalts promoted many aspects of wound repair when infection is not present (Figure 2). The ability of Ag Oxysalts to directly produce oxygen and to catalyze the breakdown of H 2 O 2 to oxygen and water may create a more favorable wound environment that is sufficient to shift a stalled wound out of the inflammatory phase and progress to healing. 4

5 Clinical Cases Case One A 70-year-old female presented with medical and surgical history of PAD, renal transplant on immunosuppressants, renal insufficiency, peripheral neuropathy, aortic stenosis, hypertension, cardiac stents x 3, ABI of 0.6, and multiple LE wounds over several months to years. Previous treatments included enzymatic debriding agents, 1+ silver ionic dressings, and alginate. She was on a course of intravenous antibiotics before the use of Ag Oxysalts. She first presented to the clinic on August 26, The wound size was 15.1 x 15.1 x 0.3 cm at its greatest size in early April 2017 (Figure 3). The peri-wound tissue was hardened and edematous. The wound bed had 90% slough and was malodourous. Ag Oxysalts gel dressing was applied to her wound on her April 24, 2017 visit with no compression due to severe PAD and low ABI. Full closure of the wound was achieved on September 11, 2017 (Figure 4). Case One Case Two A 75-year-old female presented with a past medical and surgical history of hypertension, Crohn's disease, proctocolectomy, osteoarthritis, and DVT with venous insufficiency ulceration involving the left lateral leg. She had different treatments used, including serial debridement, dressings that included honey-based dressings, silver foam, collagen-based dressings, and 1+ silver alginate dressings without much improvement. Compression was done using Coban wraps. The wound was biopsied. The pathology was suggestive of venous insufficiency. The patient underwent vein evaluation and subsequent laser treatment for venous insufficiency. On April 26, 2018 (Figure 5), patient had a wound involving the left lateral leg measuring 6.2 x 3.2 x 0.1 with 60% necrotic tissue and 40% granulation tissue. Ag Oxysalts gel dressing was initiated. The wound was then covered with a secondary absorptive dressing and compression wraps were then applied. On July 26, 2018 (Figure 6), the wound measurements improved to 0.4 x 2.0 x 0.2 with 70% granulation tissue and 30% necrotic tissue. Case Two Figure 3. April 24 visit, first KerraCel Ag application. Figure 5. April 26 visit, first KerraCel Ag application. Figure 4. Early September visit, just prior to closure. Figure 6. July 26 visit, just prior to closure. 5

6 An HCP Perspective Elemental silver in the Ag 0 format is a stable molecule and is relatively nonreactive. During the 1990s, for medical and healthcare purposes, elemental silver was developed into an ionic silver, a more reactive version and the only form of antimicrobial silver. This technology provided a way for silver compounds to be delivered in dressings and broken down into ions when exposed to wound fluid or an aqueous solution. The ions are an Ag 1+ electron format and can kill bacteria by rupturing the cell wall, inhibiting vital enzymes, destroying cells using free radicals, or interacting with the bacteria s DNA. The mechanism of action (MOA) of newly engineered Ag Oxysalts technology makes highly oxidative states of silver ions (Ag 1+, Ag 2+, Ag 3+ ) available; thus, the silver is more powerful and can work faster while using a fraction of the amount of silver compared to other ionic silver formats 3,4 (Figure 7). From an individual HCP perspective and after reviewing the MOA, the following questions can be asked to help one analyze the value of this new technology. These questions are based on experiences using silver dressings in clinical practice and teaching the antimicrobial properties of silver in pre- and post-professional coursework. Because of the historical challenges regarding the use of silver dressings in the literature, the questions were related to cytotoxicity and healthy tissue, resistance of microbes to silver, and the ability to disrupt a biofilm, not just planktonic bacteria. Figure 7. Ag Oxysalts before and after they are exposed to moisture. The moisture immediately initiates a release of oxygen molecules, which is currently being studied to understand the effects in the wound bed. Figure 8. Scanning electron microscopy shows control skin is covered with a thick layer of Psuedomonas aeruginosa. Figure 9. After treatment with Ag Oxysalts, the collagen fibers are clearly visible with few bacteria. 6

7 minimal to no bacterial resistance. Upon evaluation of the MOA, published peer-reviewed literature, and clinical case support from other trusted HCPs, one could reasonably be encouraged to use this technology in clinical practice. Figure 10. Significantly less viable bacteria was noted after 24 hours of Ag Oxysalts treatment. Is this technology cytotoxic to healthy tissue and will it impair healing? Thomason et al 14 presented in vivo and in vitro data to support use of the Ag Oxysalts technology without impaired healing or cytotoxicity. Improved healing was demonstrated by significant decreases in wound area and increased epithelialization in full-thickness mouse wound models when the Ag Oxysalts technology was compared to a nonantimicrobial control. There also was evidence that treatment with Ag Oxysalts promoted wound healing and accelerated closure in human keratinocyte scratch wounds compared to untreated control scratch wounds. Is there bacterial resistance to this technology? Bacteria have been around for millennia and have made some extraordinary adaptations to environment and in response to repeated exposure to lethal substances. This adaptive ability is evidenced among all the multidrug-resistant (MDR) bacteria known today. Using a time-kill analysis, Kalan et al 4 found that a panel of MDR pathogens isolated from wound specimens remained susceptible to Ag 7 NO 11 over a period of 7 days, even with repeated inoculations of CFU/ ml to the dressing. 4 Finley et al 15 found that both Klebsiella pneumonia (SRKP) and Enterobacter cloacae (SREC) expressing silver-resistant genes were highly resistant to 7 of 9 silver dressings; silver oxysalt dressing was among the silver dressings to which the SRKP and SREC remained sensitive. Does this technology effectively disrupt biofilms? Dressings that contain higher oxidative states of silver (Ag 1+, Ag 2+, Ag 3+ ) with Ag Oxysalts were found to be more effective against planktonic bacteria and bacteria within wound biofilms than another Ag 1+ dressing. 16 Mature Pseudomonas aeruginosa biofilms in a porcine ex vivo model were found to have statistically significantly less bacteria (P <.05) than the control 24 hours after application of Ag Oxysalts (Figures 8 10). HCPs and educators who have evaluated many wound care products can conclude that the unique chemical qualities of the Ag Oxysalts compound allow it to perform as an effective antimicrobial, disrupting biofilm and improving wound healing processes without cytotoxicity and with References 1. Gibbard J. Public health aspects of the treatment of water and beverages with silver. Am J Public Health Nations Health. 1937;27(2): Xiu ZM, Zhang QB, Puppala HL, Colvin VL, Alvarez PJ. Negligible particle-specific antibacterial activity of silver nanoparticles. Nano Lett. 2012;12(8): Lemire JA, Kalan L, Bradu A, Turner RJ. Silver oxynitrate, an unexplored silver compound with antimicrobial and antibiofilm activity. Antimicrob Agents Chemother. 2015;59(7): doi: /aac Kalan L, Pepin D, UI-Haq I, Miller SB, Hay ME, Precht RJ. Targeting biofilms of multidrug-resistant bacteria with silver oxynitrate. Int J Antimicrob Agents. 2017;49(6): Djokić SS. Deposition of silver oxysalts and their antimicrobial properties. J Electrochem Soc. 2004;151(6):C doi: / Jack J, Kennedy T. The thermal analysis of argentic oxynitrate and silver oxides. J Thermal Analysis. 1971;3(1): doi: / issue- 1;wgroup:string:metapress;page:string:Article/Chapter. 7. Noyes AA, Hoard JL, Pitzer KS. Argentic salts in acid solution. I. The oxidation and reduction reactions. J Am Chem Soc. 1935;57(7): doi: /ja01310a Noyes AA, Pitzer KS, Dunn CL. Argentic salts in acid solution. II. The oxidation state of argentic salts. J Am Chem Soc. 1935;57(8): doi: /ja01310a Noyes AA, Kossiakoff A. Argentic salts in acid solution. III. Oxidation potential of argentous argentic salts in nitric acid solution. J Am Chem Soc. 1935;57(7): doi: /ja01310a Vanysek P. Electrochemical series. In: Rumble R, eds. CRC Handbook of Chemistry and Physics, 98th ed. Boca Raton, FL: CRC Press/Taylor & Francis; Sen CK. Wound healing essentials: let there be oxygen. Wound Repair Regen. 2009;17(1): Thomason HA, Lovett JM, Spina CJ, Stephenson C, McBain AJ, Hardman MJ. Silver oxysalts promote cutaneous wound healing independent of infection. Wound Repair Regen. 2018;12. doi: /wrr [Epub ahead of print]. 13. Schäfer M, Werner S. Oxidative stress in normal and impaired wound repair. Pharmacol Res. 2008;58(2): Cano Sanchez M, Lancel S, Boulanger E, Neviere R. Targeting oxidative stress and mitochondrial dysfunction in the treatment of impaired wound healing: a systematic review. Antioxidants (Basel). 2018;7(8):pii:E Finley PJ, Norton R, Austin C, Mitchell A, Zank S, Durham P. 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8 Powered by Ag Oxysalts visualized by scanning electron microscopy. 200 nm EHT=10.00 kv WD= 5.8 mm Signal A=SE2 Mag=50.00 K X Oxygen (O 2 ) is shown on the surface of Ag Oxysalts. This O 2 is produced from the breakdown of Hydrogen Peroxide (H 2 O 2 ) and the reaction of Ag Oxysalts. 1 Silver to the Power of 3+ KerraCel Ag dressing combines a carboxymethyl cellulose (CMC) gelling fiber dressing with Ag Oxysalts technology. Ag Oxysalts (Ag 3+ ), provides UP TO 6 TIMES MORE POWER than traditional silvers (Ag 1+ ) to reduce barriers that create a hostile wound environment. *, 2 INFECTION BIOFILM PERSISTENT INFLAMMATION Quickly kills at least % (5 log) of a broad spectrum of bacteria in vitro 3,4,5 Effectively kills bacteria within a biofilm and prevents biofilm re-formation in vitro 6,7 Reduces inflammation (in vivo) and H 2 O 2 (in vitro) that cause tissue damage and support microbial growth. 1 * As demonstrated in vitro us.info@crawfordhealthcare.com References: 1. Thomason H, Lovett, J et al. Silver oxysalts promote cutaneous wound healing independent of infection. Wound Repair and Regeneration Spina C. Silver I, II, III: Chemical characteristics, properties, and anti-microbial activity. Data on file. Crawford Healthcare Ltd. 3. Antibacterial efficacy of KerraCel Ag against planktonic species over 7 days in vitro. CHC R Data on file. Crawford Healthcare Ltd. 4. Rate of antibacterial efficacy of KerraCel Ag against S. aureus and P. aeruginosa in vitro. CHC R Data on file. Crawford Healthcare Ltd. 5. Evaluation of antimicrobial activity of KerraCel Ag against multi-drug resistance organisms. CHC R Data on file. Crawford Healthcare Ltd. 6. Evaluation of antimicrobial activity of KerraCel Ag against in vitro biofilms. CHC R Data on file. Crawford Healthcare Ltd. 7. Evaluation of antimicrobial activity of KerraCel Ag against biofilms in a porcine ex vivo model. CHC R KerraCel is a registered trademark of Crawford Healthcare Ltd. Ag Oxysalts is a trademark of Argent LP. Crawford Healthcare Ltd, CH18509-US