COPPER-CONTAINING GLASS CERAMIC WITH HIGH ANTIMICROBIAL EFFICACY

• Published in: Paint & Coatings Industry 2019-10, Vol.35 (10), p.44-53
• Main Authors: Gross, Timothy M, Lahiri, Joydeep, Golas, Avantika, Luo, Jian, Verrier, Florence, Kurzejewski, Jackie L, Baker, David E, Wang, Jie, Novak, Paul F, Snyder, Michael J
• Format: Magazinearticle
• Language: English
• Subjects: Amorphous materials; Antibiotics; Antiinfectives and antibacterials; Antimicrobial agents; Atoms & subatomic particles; Bacteria; Bedrock; Biocompatibility; Cell membranes; Composite materials; Contamination; Copper; Crystal structure; Crystallinity; Crystals; Damage; Disruption; DNA; Drug resistance; Field strength; Glass ceramics; Health aspects; Hydroxides; Hydroxyl radicals; Hygiene; Infection; Infection control; Ion exchange; Microbial drug resistance; Microorganisms; Nosocomial infections; Packing density; Pathogenic microorganisms; Pathogens; Phosphorus; Plasmids; Potassium; Protective coatings; Silica; Solid surfaces; Species diffusion; Spectrum analysis; Staphylococcus infections; Test procedures; Toxicity
• ISSN: 0884-3848; 2328-8329

Nosocomial infections and the emergence of antibiotic-resistant strains pose significant clinical and economic challenges.1,2 While good hygiene practices are the bedrock for infection control, emerging evidence suggests that continuously killing antimicrobial surfaces based on metallic copper can reduce bioburden and lower the risk of infection.3 Copper's multiple mechanisms of action, which includes the ability to destroy genomic and plasmid DNA,4 explain its longstanding antimicrobial efficacy against pathogens such as antibiotic-resistant "superbugs".5,6 Proposed mechanisms for copper-mediated cellular damage and toxicity include direct cell membrane damage, the generation of reactive hydroxyl radicals through Fenton-type reactions, and entry of copper ions into cells through ligand interactions, causing disruption of RNA and DNA function.5"7 While the precise mechanism is unclear, Cu1+ ions are considerably more toxic to bacteria than Cu2+ ions under test conditions that mimic microbial contamination on solid surfaces.8"10 There has been a significant focus on metallic copper as an antimicrobial since the U.S. EPA introduced a new test protocol in 2008 that was exclusively passed by copper surfaces.11,12 The U.S. EPA mandated that claims of efficacy against human pathogens could only be obtained for products that pass the standard with the justification that it was a realistic simulation of contamination unlike the traditional test.6,13 We wanted to make a copper-containing additive compatible with commonly used surfaces and coatings that demonstrated the efficacy to kill >99.9% of bacteria under EPAs test conditions retaining copper's broad spectrum efficacy and low probability for the development of resistant strains.5,14 We describe an alkali copper aluminoborophospho-silicate glass ceramic material that acts as a sustainable delivery system for Cu+1 ions with high antimicrobial efficacy. When a glass is cooled from the molten state, the oxygen packing density of the glass network is increased as ionic field strength of modifier ions such as Cu1+ increases, resulting in smaller interstitial spaces surrounding the modifiers. Since inter-diffusion of charged species requires charge neutrality,25 the H30+/ R1+ (R = Li, Na, K, Cu, etc.) ion exchange is effectively stopped if the larger ion cannot enter the site that forms around the smaller, higher field strength ion. XRD confirmed that the crystalline phase was cuprite (Cu20) for sample E (Figure 2a i