Note Preparation of cetylpyridinium montmorillonite for antibacterial applications Günseli Özdemir a, ⁎, Saadet Yapar a , Mine Hoşgör Limoncu b a Ege University, Engineering Faculty, Chemical Engineering Department, 35100 Izmir, Turkey b Ege University, Faculty of Pharmacy, Department of Pharmaceutical Microbiology, 35100 Izmir, Turkey abstract article info Article history: Received 24 May 2012 Received in revised form 11 January 2013 Accepted 12 January 2013 Available online 7 March 2013 Keywords: Antibacterial activity Montmorillonite Cetylpyridinium chloride Adsorption–desorption Staphylococcus aureus Pseudomonas aeruginosa The antibacterial activities of cetylpyridinium-montmorillonites (CP + -Mt) were tested on Staphylococcus aureus and Pseudomonas aeruginosa. The Mt were prepared by using the five different CP + amounts of 0.5, 0.7, 1.0, 1.5, and 2.0 times of cation exchange capacities (CEC) of Na + -Mt. Desorption of CP + from the surface was also determined by successive adsorption–desorption experiments. The antibacterial activity tests were conducted by using Na + -Mt and CP + -Mt through the disk diffusion (Kirby–Bauer) method against the P. aeruginosa ATCC 27853, and S. aureus ATCC 29213 strains. XRD analyses of the CP + -Mt showed that basal spacing regularly increased by increasing the amount of CP + cations. Adsorption/desorption studies revealed that desorption occurred only in 2.0 CEC CP + -Mt by dilution with water and in 1.0 CEC CP + -Mt at a pH of 2.0. Na + -Mt exhibited no antibacterial activity against both bacteria. All of the CP + -Mt samples prepared were ac- tive against S. aureus, whereas they had no antibacterial activity against P. aeruginosa. Minimum inhibitory concentration (MIC) was found to be 1 mg/plate against S. aureus, determined with 0.5 CEC CP + -Mt. Because nearly no desorption of CP + was observed, the antibacterial activity was attributed to the CP + bound to the Mt surface. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Microbial contamination and infection is a serious concern for the food industry and medical applications. In most of the antimicrobial applications eluting agents are used. Cetylpyridinium chloride (CPC) as a quaternary ammonium salt is such an agent used in antiseptic solu- tions, and finds a wide range of antibacterial applications in oral rinses and throat lozenges (Kudiyirickal and Ivancakova, 2008; Michael et al., 1996), in antibacterial liquid soaps for hand washing, in contact lens care solutions and synthetic tear drops, in the meat industry for the decontamination of carcasses, and in the further processing of poultry, pork, and beef for the control of microbial growth (McElyea et al., 2002; Waldroup et al., 2010). Quaternary ammonium ions act by penetrating the cell membrane, causing leakage of cell components, disruption of the bacterial metabolism, inhibition of cell growth, and cell death (Hamouda and Baker, 2000; Merianos, 1991; Watanabe et al., 2008). Although the eluting biocides are superior for many applications, immobilized antimicrobial agents introduce some advantages such as elimination of patient exposure to elutable biosites, reduction in their irritant properties and potential increase in the duration of antibacterial efficacy (Green et al., 2011). Metals, polymers, textiles and minerals such as clays and zeolites are used as host material in the immobilization. Although the recent studies on antibacterial ac- tivities of clay based materials are mainly focused on immobilization of inorganic cations such as Ag + , Cu 2+ , and Zn 2+ (Hu and Xia, 2006; Hu et al., 2005; Magaña et al., 2008; Malachová et al., 2009; Özdemir et al., 2010; Tong et al., 2005; Zhao et al., 2006; Zhou et al., 2004) onto clay minerals, immobilization of organic cations with antibacterial activity has some advantages compared to that of inorganic cations. First of all, organic antibacterial materials impart organophilicity and compatibility to clay minerals with an organic matrix such as textiles, paints, paper and polymers (He et al., 2006) and thus they have the potential to be used in relevant industries with more pur- pose oriented applications, and longer lasting antibacterial activity. Besides these materials act not only against the bacteria, they also ad- sorb both natural and anthropogenic toxins. The antibacterial activity of quaternary ammonium ions depends on their adsorbed amount on the montmorillonite (Mt) surface (Özdemir et al., 2010) and Na + -Mt with a high surface area and ion-exchange capacity provides a strong binding of quaternary alkylammonium ions on to the negatively charged surfaces as well as high surface concentration. However, there are only a few studies about their antibacterial abilities (He et al., 2006; Herrera et al., 2000; Malachová et al., 2009; Namba et al., 2009). The aim of this study was to reveal how effective CP + -Mt was against Staphylococcus aureus and Pseudomonas aeruginosa. Both bac- teria are major human pathogens, responsible for a number of hos- pital infections. S. aureus colonize at several locations in the human Applied Clay Science 72 (2013) 201–205 ⁎ Corresponding author. Tel.: +90 232 388 76 00; fax: +90 232 388 77 76. E-mail addresses: gunseliozdemir3@gmail.com (G. Özdemir), saadet.yapar@ege.edu.tr (S. Yapar), mine.hosgor.limoncu@ege.edu.tr (M.H. Limoncu). 0169-1317/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.clay.2013.01.010 Contents lists available at SciVerse ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay