Organic-Inorganic Hybrid Films Fabricated from Cellulose Fibers and Imogolite Nanotubes.

Owing to the increasing environmental awareness, nanocellulose/natural clay composites with improved mechanical performance have attracted growing interest due to their eco-friendly properties. In this study, hybrid films composed of cellulose fibers (CFs) and imogolite nanotubes (natural aluminosilicate nanotubes) were fabricated. We mainly studied the structure, density, and properties of the hybrid materials. Specifically, the hybrid materials were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), a rheological test, and wide-angle X-ray diffraction (WAXD). The mechanical properties of the hybrid materials were measured by a tensile test, which demonstrated that the mechanical properties of the hybrid films were considerably improved by the addition of imogolite up to 1 wt %; meanwhile, the thermal-mechanical properties of the hybrid film were also enhanced.

Intracellular periodontal pathogen exploits recycling pathway to exit from infected cells.

Although human gingival epithelium prevents intrusions by periodontal bacteria, Porphyromonas gingivalis, the most well-known periodontal pathogen, is able to invade gingival epithelial cells and pass through the epithelial barrier into deeper tissues. We previously reported that intracellular P. gingivalis exits from gingival epithelial cells via a recycling pathway. However, the underlying molecular process remains unknown. In the present study, we found that the pathogen localized in early endosomes recruits VAMP2 and Rab4A. VAMP2 was found to be specifically localized in early endosomes, although its localization remained unclear in mammalian cells. A single transmembrane domain of VAMP2 was found to be necessary and sufficient for localizing in early endosomes containing P. gingivalis in gingival epithelial cells. VAMP2 forms a complex with EXOC2/Sec5 and EXOC3/Sec6, whereas Rab4A mediates dissociation of the EXOC complex followed by recruitment of RUFY1/Rabip4, Rab4A effector, and Rab14. Depletion of VAMP2 or Rab4A resulted in accumulation of bacteria in early endosomes and disturbed bacterial exit from infected cells. It is suggested that these novel dynamics allow P. gingivalis to exploit fast recycling pathways promoting further bacterial penetration of gingival tissues.

Antibacterial Activity of Curcumin Against Periodontopathic Bacteria.

BACKGROUND: Curcumin is a polyphenol extracted from root of turmeric and known to possess multifunctional properties, including antibacterial activity. Although previous studies have investigated the effects of curcumin on microorganisms, available knowledge on the effects of curcumin on periodontopathic bacteria is still limited. In this study, the antibacterial effect of curcumin on periodontopathic bacteria is investigated, particularly Porphyromonas gingivalis. METHODS: Representative periodontopathic bacteria were cultured in media with and without various curcumin concentrations, and the optical density at 600 nm was measured for 60 hours. The inhibitory effect of curcumin on P. gingivalis Arg- and Lys-specific proteinase (RGP and KGP, respectively) activities were assessed using spectrofluorophotometric assay. Analysis of biofilm formation by P. gingivalis with or without Streptococcus gordonii was conducted using confocal laser-scanning microscopy (CLSM). RESULTS: Curcumin inhibited the growth of P. gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Treponema denticola in a dose-dependent manner. Bacterial growth was suppressed almost completely at very low concentrations of curcumin. Conversely, 100 µg/mL curcumin did not suppress the growth of Aggregatibacter actinomycetemcomitans. It also demonstrated inhibitory effects against RGP and KGP activities in a dose-dependent manner. CLSM revealed that curcumin suppressed P. gingivalis homotypic and P. gingivalis-S. gordonii heterotypic biofilm formation in a dose-dependent manner. A concentration of 20 µg/mL curcumin inhibited these P. gingivalis biofilm formations by >80%. CONCLUSION: Curcumin possesses antibacterial activity against periodontopathic bacteria and may be a potent agent for preventing periodontal diseases.

Fabrication and characterization of polysaccharide ion gels with ionic liquids and their further conversion into value-added sustainable materials.

A review of the fabrication of polysaccharide ion gels with ionic liquids is presented. From various polysaccharides, the corresponding ion gels were fabricated through the dissolution with ionic liquids. As ionic liquids, in the most cases, 1-butyl-3-methylimidazolium chloride has been used, whereas 1-allyl-3methylimidazolium acetate was specifically used for chitin. The resulting ion gels have been characterized by suitable analytical measurements. Characterization of a pregel state by viscoelastic measurement provided the molecular weight information. Furthermore, the polysaccharide ion gels have been converted into value-added sustainable materials by appropriate procedures, such as exchange with other disperse media and regeneration.