XPS characterization of benzethonium and cetylpyridinium-lauroyl sarcosinate-loaded organomontmorillonites and their antibacterial properties against <i>Actinomyces viscosus</i> and <i>Bacteroides fragilis</i>

Abstract Organomontmorillonite-type (O-Mnt) antibacterial agents are less susceptible to development of resistance by bacteria. The aim of the present study was to test the effects of O-Mnt samples, which were reported to be effective against Staphlococcus aureus and Streptococcus mutans in previous studies and to act as a scavenger for opportunistic pathogenic microorganisms, Actinomyces viscosus and Bacteroides fragilis , which cause severe infections such as periodontal diseases, endocarditis, and lung infections. O-Mnt samples with single and mixed surfactant layers, namely benzethonium montmorillonite (Mnt-BZT) and cetylpyridinium and N-lauroyl sarcosinate montmorillonite (Mnt-CP-SR), were subjected to X-ray diffraction, thermogravimetric analysis, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and zeta potential analyses to determine some key structural properties. Within the scope of the present study, detailed X-ray photoelectron spectroscopy (XPS) analyses were performed to elucidate the external surface structures, which are important in explaining their antibacterial properties. There have been few studies on XPS analysis in terms of types of surfactants used in O-Mnt preparation. These analyses made it possible to estimate the interaction between the surfactants on the external surface and the bacterial cell wall leading to lysis. A. viscosus , a facultative anaerobe, and B. fragilis , a strict anaerobe, required specific culture conditions, and their antibacterial susceptibility testing was conducted with caution due to challenges in isolation and antimicrobial resistance. Antibacterial susceptibility tests including the agar well diffusion test, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) determinations and time-kill assay showed that both OMnt samples were effective against the bacteria used. The XPS analyses of the exterior surface structure of O-Mnt revealed that contact killing was the mechanism of antibacterial effect. In vitro cytotoxicity and in vivo animal studies indicated that both O-Mnt samples can be used safely as antibacterial agents in oral and topical applications.