Antibacterial Coatings

Antibacterial Coatings Bacteria are single-celled microscopic organisms that we encounter frequently in daily life, found everywhere from refrigerators to washing machines, carpets to ceramic surfaces. Pathogenic microorganisms colonizing a surface create a biofilm layer. This condition causes serious clinical infections in humans. Furthermore, the resistance that pathogenic microorganisms develop against antibiotics hinders the treatment of microbial infections. Microbial contamination is one of the most significant problems in medical devices, healthcare services, hygiene-critical applications, hospital and dental surgical instruments, water treatment systems, air conditioning, ventilation systems, food packaging and food storage, and textile materials [Hos]. [caption id="attachment_149991" align="aligncenter"] Figure 1. A) Bacterial example B) Schematic representation of bacterial structure C) Schematic representation of biofilm formation.[/caption] Hospital infections (nosocomial infections) are infections that develop after hospital admission, not during the incubation period at the time of admission, or that emerge after discharge. Most commonly, these infections develop 48-72 hours after hospital admission and within 10 days of discharge. The cause of these infections is bacterial colonization on biomedical surfaces in 4-10 percent of cases (this rate reaches 30 percent in intensive care units). According to 2011 data, approximately 722,000 nosocomial infection cases occurred in the United States. Approximately 75,000 of these cases resulted in death [Cloutier et al., Magill et al.]. Textile materials provide highly favorable environments for microorganism growth, and microorganisms can survive on textile surfaces for months. While microorganisms cause changes in textile material properties (loss of strength, odor, color change), they also negatively affect the user. Following a clinical study, 65 percent of nurses caring for patients with MRSA infections were found to carry the MRSA pathogen on their gowns [Boryo]. In recent years, the development of antibacterial coatings has become an actively researched area for solving these problems. There are three main strategies for antibacterial coating designs. These are antimicrobial agent release, contact killing, and anti-adhesion/bacteria-repellent. In antimicrobial agent release (release-based coatings), coatings demonstrate antibacterial activity by leaching loaded antimicrobial compounds over time. This causes both attached and planktonic bacteria in the vicinity to die. The release of conjugated antimicrobial agents occurs through diffusion into aqueous environments, erosion/degradation, or hydrolysis of covalent bonds. The most commonly used antimicrobial compounds include antibiotics (aminoglycosides, quinolones, penicillins, glycopeptides, etc.), antimicrobial peptides, elements (silver, copper, zinc, gallium, selenium, halogens), enzymes (lysozyme, acylase), and organic cationic compounds [quaternary ammonium compounds (QAC), chlorhexidine, octenidine, chitosan]. In the contact killing approach, antimicrobial compounds are covalently bound to the material surface via flexible, hydrophobic polymer chains. It is believed that the attached bacterium dies because the bound compound damages the cell membrane. Cationic compounds like chitosan or enzymes are preferred for use. In the anti-adhesion/bacteria-repellent approach, mechanisms that prevent early biofilm formation without killing surface microorganisms are fundamentally used. In other words, non-cytotoxic mechanisms are employed to prevent biofilm formation at its earliest stage. Bacterial adhesion on biomaterial surfaces is typically described using a two-stage model: A first, rapid and reversible stage mediated by non-specific physicochemical interactions (Stage I). The second stage is the 'locking' phase (Stage II) and comprises species-specific bacterial adhesion proteins. Materials such as PEG, oxazoline, nitroxide radicals, and chlorinated plasma polymers are cited as examples [Cloutier et al.]. [caption id="attachment_149992" align="aligncenter"] Figure 2. Three main strategies developed for antibacterial coating designs: (A) Antimicrobial agent release (B) Contact killing (C) Anti-adhesion/bacteria-repellent.[/caption] Products with antibacterial properties are generally manufactured from metal, ceramic, polymer, and composite materials. These products can be prepared using two different methods. The first is manufacturing the entire product from antibacterial-property material. In this method, depending on the material used and its composition, high cost makes the method disadvantageous. For this reason, the second method—applying antibacterial coatings onto a finished surface—is more advantageous. Commonly used coating techniques include dipping, spraying, chemical vapor deposition (CVD), physical vapor deposition (PVD), sol-gel, electrophoretic deposition, and tape casting. Apart from coating applications, it is also possible to impart desired properties to the surface by functionalizing the surface or applying different techniques such as etching or implantation and plasma treatments. Antibacterial coatings are fundamentally aimed at protecting human health and can be readily obtained depending on the application location and purpose. Research on antibacterial coatings is increasing daily. The need to increase the durability of coatings and insufficient clinical studies on coatings are seen as areas requiring further development. References • Hos. A., Production of Antibacterial Polycaprolactone-Hydroxyapatite Composite Films, Sakarya University Institute of Science, 2016. • M. Cloutier, D. Mantovani, F. Rosei., 2015, Antibacterial Coatings: Challenges, Perspectives, and OpportunitiesTrends in Biotechnology, 33, 1, 637. • Magill, S.S. et al. 2014, Multistate point-prevalence survey of health care-associated infections. N. Engl. J. Med. 370, 1198–1208 • Boryo, D. 2013, The Effect of Microbes on Textile Material: A Review on the Way-Out So Far, The International Journal Of Engineering And Science, 2319, 1805. • Lichter, J.A. et al. 2009, Design of antibacterial surfaces and interfaces: polyelectrolyte multilayers as a multifunctional platform. Macromolecules 42, 8573–8586 • https://www.chemistryworld.com/news/giant-long-lived-bacteria-could-makemicrobial-farms-more-productive/4011137.article • https://micro.magnet.fsu.edu/cells/bacteriacell.html • https://www.cs.montana.edu/webworks/projects/stevesbook/contents/chapters/chapter001/section002/black/page001.html • https://www.tucsa.org/images/sss/ÇELİK%20YÜZEYLERİN%20MİKROPLARDAN%20KORUNMASI%20DEZENFEKSİYON,%20DEZENFEKTALAR,%20ANTİMİKROBİYAL%20BOYALAR%20ve%20KAPLAMALAR.pdf • https://www.ideaport.org.tr/img/blog/61d2a730db781.pdf Assoc. Prof. Ekrem Altuncu TÜYİDER (Association of All Surface Treatment) Board Member Sakarya University of Applied Sciences Director of Materials and Manufacturing Technologies Application and Research Center – SUMAR Dr. Nilay Tüccar Kılıç Sakarya University of Applied Sciences Materials and Manufacturing Technologies Application and Research Center