title: Clay mineral particles as effficient carriers of methylene blue used for antimicrobial treatment.
abstract: There is a strong demand to identify new strategies for disinfection and treatment of human, animal, and plant pathogens. The presented work shows the potential of clay minerals to contribute to the development of novel disinfection materials. Enhanced antimicrobial effect of a photoactive organic dye, methylene blue (MB), in the colloids of clay mineral was observed. Singlet oxygen (1O2) formed upon visible light irradiation was detected directly using luminescence measurements atthe near-infrared region and by spin-trapping method. While MB adsorbed on clay colloid particles lost the ability to produce 1O2 due to molecular aggregation, surprisingly, the antimicrobial activity was significantly enhanced. Under visible light irradiation, MB/clay minerals dispersions prevented the sporulation of A. niger and Penicillium sp. and inhibited the growth of C. albicans by an additional 6-15% when compared with MB solution. In the experiments with E. coli, the efficiency of MB was increased by the reduction of surviving cells by 27 and 33%. S. aureus proved to be the most susceptible to MB/clay dispersions. Only less than 20% cells survived with respect to the control experiment at the low MB concentration (1.1 x 10(-6) mol dm(-3)). The contradiction between the significant antimicrobial properties of MB in clay colloidal systems and low 1O2 formation can be explained in terms of the photosensitization mechanism. The role of clay particles is most likely to promote the contact between microorganism cells and photoactive MB. Although the dye directly bound to the clay surface exhibits significantly reduced photoactivity, the presence of clay mediates the delivery of dye molecules on the surface or inside cells. The results indicate new perspectives of potential implementations of clay minerals as parts of complex disinfection materials for industrial applications or in understanding similar processes in nature.
authors.affiliation: Institute of Inorganic Chemistry, Slovak Academy of Sciences, 845 36 Bratislava, Slovakia.
authors.forename: Juraj
authors.initials: J
authors.lastname: Bujdák
authors.forename: Jana
authors.initials: J
authors.lastname: Jureceková
authors.forename: Helena
authors.initials: H
authors.lastname: Bujdákova
authors.forename: Kamil
authors.initials: K
authors.lastname: Lang
authors.forename: Frantisek
authors.initials: F
authors.lastname: Sersen
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000166:cytology / Q000187:drug effects; D000077215:Clay; D003102:Colloids; D004337:Drug Carriers / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005658:Fungi / Q000166:cytology / Q000187:drug effects; D008751:Methylene Blue / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D008903:Minerals / Q000737:chemistry*; D026082:Singlet Oxygen; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013172:Spores, Fungal / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: D000538:Aluminum Silicates; D000900:Anti-Bacterial Agents; D003102:Colloids; D004337:Drug Carriers; D008903:Minerals; D012996:Solutions; D026082:Singlet Oxygen; D000077215:Clay; D008751:Methylene Blue