The use of Ag 5 IO 6 as an antibiofilm agent in wound dressings V. Incani * , A. Omar * , G. Prosperi-Porta *,** and P. Nadworny * * Innovotech, Inc., Suite 101, 2011 94 St., Edmonton, AB, Canada **Department of Chemical and Materials Engineering, University of Alberta, 7 th Floor Electrical and Computer Engineering Research Facility, 9107 116 St., Edmonton, AB, Canada E-mails: vanessa.incani@innovotech.ca, amin.omar@innovotech.ca, prospeg@mcmaster.ca Corresponding author: patricia.nadworny@innovotech.ca ABSTRACT The novel antibiofilm activity of Ag 5 IO 6 was explored. Wound dressings impregnated with Ag 5 IO 6 were compared to commercially available silver, chlorhexidine, and PHMB dressings. The dressings were tested against P. aeruginosa, S. aureus, and C. albicans for their ability to prevent microorganism adherence, eliminate planktonic species, and eliminate mature biofilms within 24h. Only the Ag 5 IO 6 dressings were able to prevent adherence and eliminate surrounding planktonic microorganisms for all species tested for ≥28 days of elution with log reductions >4. Moreover, only these dressings were able to generate >4 log reductions against all mature biofilms. Thus, Ag 5 IO 6 has superior activity to a number of antimicrobials, with long-term prevention of microbial adherence, rapid kill of planktonic microorganisms, and the ability to eliminate mature biofilms. Ag 5 IO 6 may be a valuable antimicrobial agent for use in a number of medical device applications, including catheters, and implants. Keywords: Silver periodate, antimicrobial, wound dressing, infection, biofilm 1 INTRODUCTION Silver agents as topical antimicrobials have been used for hundreds of years in wound care [1]. Silver has been used to prevent or manage infection in its solid elemental form, as solutions of silver salts used to cleanse wounds, and more recently as creams or ointments containing a silver-antibiotic compound. However, these applications of silver have come with considerable challenges that include complex methods for incorporation/coating of silver into/onto materials, lack of efficacy against planktonic microorganisms and biofilms in part due to inactivation by bodily fluid components [2, 3], cost effectiveness, and questions about safety [1]. Recently, numerous new silver compounds/products have been developed and added to medical devices in efforts to overcome these obstacles, mostly as antibiotic alternatives in the face of limited antimicrobial spectrum and growing microbial resistance. Bacteria exist predominantly in biofilms [4]. Biofilms are responsible for 80% of human infections [5], and are typically 100-1000x more resistant to treatment than planktonic microorganisms [6]. Therefore, when testing new silvers for potential clinical relevance, they need to demonstrate efficacy against biofilm phenotypes. Ag 5 IO 6 (pentasilver hexaoxoiodate) possesses promising properties for efficacy against biofilms, and simplicity for coating onto/incorporating into medical devices with approriate release characteristics. These properties include the presence of silver in both cation ([Ag 3 ] 3+ ), and anion-complexed with highly oxidized iodine ([Ag 2 IO 6 ] 3- ) [7]. This may enhance penetration of the biofilm relative to Ag + , which binds to negatively charged surface components of biofilms. The periodate structure around the anionic silver may slow its inactivation by bodily fluid components. Combining silver and iodine may increase antimicrobial mechanisms of action, reducing the likelihood of developing resistance to Ag 5 IO 6 . The synthesis method used here combines small grain size with large particle size, resulting in polycrystallinity on a large surface area which may improve its antimicrobial activity relative to other Ag-compounds. Ag 5 IO 6 has demonstrated excellent stability (storage; thermal; and in the presence of light, water, saline, organic solvents, autoclaving, ethylene oxide, etc.), and can be easily synthesized with high purity in a form that is simple to deposit onto metals or incorporate into wound dressings, gels, polymers, etc. [8] This study examined whether Ag 5 IO 6 could prevent biofilm formation on surfaces and eliminate mature biofilms, with comparison to commercially available antimicrobials to determine whether its activity was novel. 2 EXPERIMENTAL SECTION Materials. Ag 5 IO 6 was synthesized in-house [8]. Ag 5 IO 6 was coated onto two bandages - a dressing with two outer layers of high-density polyethylene (HDPE) and a rayon/polyester core (3ply-Ag 5 IO 6 ); and a rayon/cotton elastic adhesive bandage (elastic-Ag 5 IO 6 ) [9]. Commercial dressings included in testing: nanoAg, alginate-Ag, NaCMC-Ag, oxysilver, chlorhexidine, and PHMB (polyhexamethylene biguanide). Microorganisms. Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 6538, S. aureus ATCC 29213, and Candida albicans ATCC 18804. Materials for tests. 0.9% NaCl was used in pre-treatments. Human plasma (Human Male AB; SeraCare Life Sciences Inc., Gaithersburg, MD) was used 289 Biotech, Biomaterials and Biomedical: TechConnect Briefs 2015