title: Photophysical and antibacterial properties of complex systems based on smectite, a cationic surfactant and methylene blue.
abstract: Solid or colloidal materials with embedded photosensitizers are promising agents from the medical or environmental perspective, where the direct use of photoactive solutions appears to be problematic. Colloids based on layered silicates of the saponite (Sap) and montmorillonite (Mon) type, including those modified with dodecylammonium cations (C12) and photosensitizer--methylene blue (MB) were studied. Two representatives of bacteria, namely Enterobacter cloacae and Escherichia coli, were selected for this work. A spectral study showed that MB solutions and also colloids with Sap including C12 exhibited the highest photoactivities. The antimicrobial properties of the smectite colloids were not directly linked to the photoactivity of the adsorbed MB cations. They were also influenced by other parameters, such as light vs. dark conditions, the spectrum, power and duration of the light used for the irradiation; growth phases, and the pre-treatment of microorganisms. Both the photoactivity and antimicrobial properties of the colloids were improved upon pre-modification with C12. Significantly higher antimicrobial properties were observed for the colloids based on Mon with MB in the form of molecular aggregates without significant photoactivities. The MB/Mon colloids, both modified and non-modified with C12 cations, exhibited higher antimicrobial effects than pure MB solution. Besides the direct effect of photosensitization, the surface properties of the silicate particles likely played a crucial role in the interactions with microorganisms.
authors.affiliation: Comenius University in Bratislava, Faculty of Natural Sciences, Department of Microbiology and Virology, Bratislava, Slovakia.
authors.forename: Alena
authors.initials: A
authors.lastname: Donauerová
authors.affiliation: Comenius University in Bratislava, Faculty of Natural Sciences, Department of Physical and Theoretical Chemistry, Bratislava, Slovakia; Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava, Slovakia.
authors.forename: Juraj
authors.initials: J
authors.lastname: Bujdák
authors.affiliation: Comenius University in Bratislava, Faculty of Natural Sciences, Department of Microbiology and Virology, Bratislava, Slovakia.
authors.forename: Miroslava
authors.initials: M
authors.lastname: Smolinská
authors.affiliation: Comenius University in Bratislava, Faculty of Natural Sciences, Department of Microbiology and Virology, Bratislava, Slovakia. Electronic address: bujdakova@fns.uniba.sk.
authors.forename: Helena
authors.initials: H
authors.lastname: Bujdáková
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D001546:Bentonite / Q000737:chemistry; D003102:Colloids; D004305:Dose-Response Relationship, Drug; D016972:Enterobacter cloacae / Q000187:drug effects / Q000254:growth & development; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D008751:Methylene Blue / Q000737:chemistry* / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D017640:Silicates / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D000900:Anti-Bacterial Agents; D003102:Colloids; D017319:Photosensitizing Agents; D000644:Quaternary Ammonium Compounds; D017640:Silicates; D013501:Surface-Active Agents; D001546:Bentonite; C099453:saponite; C033214:Smectite; C022806:dodecyltrimethylammonium; D008751:Methylene Blue
keywords: Enterobacter cloacae; Escherichia coli; Methylene blue; Montmorillonite; Photodynamic inactivation; Saponite