Relationship between water status in dentin and interfacial morphology in all-in-one adhesives

OBJECTIVES

All-in-one adhesive systems have been recently developed to simplify bonding procedures. The adhesives containing acidic resin monomers generate a relatively thin bonding zone between dentin and composite. This zone may be left acidic and permeable when polymerization is poor. In this study, the effect of water contained in dentin on the quality of the bonding interface was morphologically investigated for all-in-one adhesives.

METHODS

Intact coronal dentin (hydrated dentin), desiccated coronal dentin (dehydrated dentin), caries-affected dentin (CAD) and resin composites were used for adherends to assess the effects of water contained in dentin on the ultra-structures of bonding interfaces created with two all-in-one adhesives and a resin composite.

RESULTS

The bonding interfaces were observed under TEM without demineralization. Voids of various sizes were found at the bottom of the adhesive resin layers along the bonding interface of hydrated dentin, while dehydrated dentin, CAD and resin composites did not generate voids. The results showed that the voids were possibly formed by water that had penetrated from the underlying dentin.

CONCLUSION

When the adherend contains little water, the formation of voids will not occur. It was verified that a phenomenon of void formation would not occur in a clinical situation in which caries-affected dentin is mainly subjected to adhesive practices.

Immobilization of nanofibrous metal oxides on microfibers: A macrostructured catalyst system functionalized with nanoscale fibrous metal oxides

Nanofibrous LaMnO(3) can be immobilized on macrostructured materials using carbon nanofibers as templates; their application as macro-nanostructured catalysts are also presented.

DNA-based gels for oral delivery of probiotic bacteria

A single-stranded DNA, readily extracted from industrial discarded salmon milt, was used to prepare hydrogels and complex gels by cross-linking with gelatin and kappa-carrageenan, for the oral delivery of probiotic bacteria. The complex gels showed a higher protective capability over the hydrogels for approximately one log scale. However, the hydrogels were more stable during storage at 4 degrees C. The Lactobacillus and Lactococcus due to protection of the hydrogels could better tolerate to acid than the Bifidobacterium. Furthermore, food-graded hydrogels were prepared and optimized to a similar protective capability for future applications.

Control of the Optical Properties of Quantum Dots by Surface Coating with Calix[n]arene Carboxylic Acids

A new method for the control of the optical properties of quantum dots (QDs) has been developed using calix[n]arene carboxylic acids (1-3) as surface coating agents for QDs. The calixarene coating of CdSe/ZnS QDs was easily performed in tetrahydrofuran at room temperature. Deprotonation of the carboxyl groups of the calixarene derivatives surrounding the QDs resulted in highly fluorescent water-soluble QDs. The emission peak of the calixarene-coated QDs shifted to longer wavelengths depending on the oligomer size of the calix[n]arene derivative used for the surface coating. Although the red shift of the emission peak decreases with the increase in the particle size of QDs, this surface coating method is useful for the preparation of multi-colored water-soluble QDs from a single-colored hydrophobic QD.

Hybrid layer seals the cementum/4-META/MMA-TBB resin interface

Although 4-META/MMA-TBB resin has adhesive properties to dentin, and has been clinically used for the bonding treatment of vertically fractured roots and apicoectomy, there has not been any investigation on the adhesion of 4-META/MMA-TBB resin to cementum. The purpose of this in vitro study was to evaluate the bonding and the sealing ability of 4-META/MMA-TBB resin to cementum. Bovine root cementum and dentin surfaces were treated with a citric acid and ferric chloride solution, and the 4-META/MMA-TBB resin was applied on the treated surfaces before testing. The microtensile bond strength and the leakage levels obtained for the cementum were almost equal to those for the dentin. In SEM and TEM observations, a hybrid layer approximately 2-3 microm in thickness was observed at the interface between the resin and the cementum. It is concluded that 4-META/MMA-TBB resin adhered to cementum via a hybrid layer on cementum, as previously reported for dentin.

Shewanella pneumatophori sp. nov., an eicosapentaenoic acid-producing marine bacterium isolated from the intestines of Pacific mackerel (Pneumatophorus japonicus)

An eicosapentaenoic acid-producing bacterium, previously described asShewanellasp. strain SCRC-2738, was classified by phenotypic characterization, chemotaxonomic analysis, 16S rRNA gene sequence analysis and DNA–DNA hybridization. The isolate was Gram-negative, rod-shaped and motile by using polar flagella. The strain grew at 4–32 °C; the optimum growth temperature was 27 °C. NaCl was required for growth. The major isoprenoid quinones were ubiquinone-7 and ubiquinone-8 and its DNA G+C content was 42·8 mol%. The whole-cell fatty acids mainly (above 5 %) consisted of iso-C13 : 0, iso-C15 : 0, C16 : 0, C16 : 1ω7c, C18 : 1ω7cand C20 : 5ω3 (eicosapentaenoic acid). Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain SCRC-2738Twas related closely (sequence similarities above 99 %) toShewanella marinintestina(99·3 %),Shewanella sairae(99·3 %) andShewanella schlegeliana(99·2 %). DNA–DNA hybridization and phenotypic characteristics confirmed that strain SCRC-2738Tmerited classification as a novel species of the genusShewanella, for which the nameShewanella pneumatophorisp. nov. is proposed. The type strain is SCRC-2738T(=JCM 13187T=NCIMB 14060T).

Oceanobacillus oncorhynchi sp. nov., a halotolerant obligate alkaliphile isolated from the skin of a rainbow trout (Oncorhynchus mykiss), and emended description of the genus Oceanobacillus

A halotolerant, obligately alkaliphilic bacterium, R-2(T), was isolated from the skin of a rainbow trout (Oncorhynchus mykiss), a freshwater fish. The strain is Gram-positive, ferments several carbohydrates, is rod-shaped and motile by peritrichous flagella and produces ellipsoidal spores. The isolate grows at pH 9-10 but not at pH 7-8. This micro-organism grows in 0-22% (w/v) NaCl at pH 10. Its major cellular fatty acids are iso-C(15:0), anteiso-C(15:0) and anteiso-C(17:0), the major isoprenoid quinone is MK-7 and the DNA G+C content is 38.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicates that strain R-2(T) is a member of the genus Oceanobacillus. DNA-DNA hybridization reveals low relatedness between the isolate and Oceanobacillus iheyensis (21.0%). On the basis of phenotypic characteristics, phylogenetic data and DNA-DNA relatedness data, the isolate should be designated as a novel species, for which the name Oceanobacillus oncorhynchi sp. nov. is proposed. The type strain is R-2(T) (=JCM 12661(T)=NCIMB 14022(T)).

Thiovirga sulfuroxydans gen. nov., sp. nov., a chemolithoautotrophic sulfur-oxidizing bacterium isolated from a microaerobic waste-water biofilm

A novel mesophilic, chemolithoautotrophic, sulfur-oxidizing bacterium, designated strain SO07(T), was isolated from a microaerobic waste-water biofilm. Chemolithoautotrophic growth was observed with elemental sulfur, sulfide and thiosulfate as sole electron donors and oxygen as electron acceptor. Anaerobic and heterotrophic growth were not observed. Nitrate was not used as a terminal electron acceptor. The optimum pH and temperature for growth were pH 7.5 and 30 degrees C, respectively. The major isoprenoid quinone was Q-8. The DNA G + C content of strain SO07(T) was 47.1 mol%. Phylogenetic analysis of 16S rRNA gene sequences demonstrated that strain SO07(T) formed a monophyletic group in the gamma-Proteobacteria with only 89 % similarity to members of the genus Halothiobacillus, its nearest phylogenetic neighbours. In addition, the isolate differed from members of the genus Halothiobacillus in its requirement for and tolerance of NaCl; strain SO07(T) was unable to grow in NaCl concentrations of more than 180 mM. On the basis of phylogenetic, chemotaxonomic and physiological data, it is proposed that isolate SO07(T) (=JCM 12417(T) = ATCC BAA-1033(T)) represents the type strain of a novel species in a new genus, Thiovirga sulfuroxydans gen. nov., sp. nov.

Alkalibacterium iburiense sp. nov., an obligate alkaliphile that reduces an indigo dye

Three indigo-reducing obligately alkaliphilic strains, M3T, 41A and 41C, were isolated. The isolates grew at pH 9–12, but not at pH 7–8. They were Gram-positive, facultatively anaerobic, straight rod-shaped strains with peritrichous flagella. The isolates grew in 0–14 % (w/v) NaCl, with optimum growth at 3–13 %. They grew at temperatures between 10 and 45 °C, with optimum growth at around 30–37 °C. They did not hydrolyse starch or gelatin.dl-lactate was the major end-product fromd-glucose. No quinones could be detected. The peptidoglycan type was A4β, Orn–d-Asp. The major cellular fatty acids were C16 : 0, C16 : 17cand C18 : 19c. The DNA G+C content was 42·6–43·2 mol%. Phylogenetic analysis based on 16S rRNA gene sequence data indicated that the isolates belong to the genusAlkalibacterium. DNA–DNA hybridization revealed low similarity (less than 16 %) of the isolates with respect to the two closest phylogenetically related strains,Alkalibacterium olivapovliticusandAlkalibacterium psychrotolerans. On the basis of phenotypic and chemotaxonomic characteristics, phylogenetic data and DNA–DNA relatedness, the isolates merit classification as a novel species of the genusAlkalibacterium, for which the nameAlkalibacterium iburienseis proposed. The type strain is M3T(=JCM 12662T=NCIMB 14024T).

Bacillus oshimensis sp. nov., a moderately halophilic, non-motile alkaliphile

A halophilic and halotolerant, facultatively alkaliphilic strain, K11(T), was isolated from soil obtained from Oshyamanbe, Oshima, Hokkaido, Japan. The isolate grew at pH 7-10. It was non-motile, Gram-positive and aerobic. Cells comprised straight rods and produced ellipsoidal spores. The isolate grew in 0-20 % NaCl, with optimum growth at 7 % NaCl, and hydrolysed casein, gelatin, starch, DNA and Tweens 20, 40, 60 and 80. The major isoprenoid quinone was menaquinone-7, and the cellular fatty acid profile consisted of significant amounts of C(15) branched-chain acids, iso C(15 : 0) and anteiso C(15 : 0). Phylogenetic analysis based on 16S rRNA gene sequencing indicated that strain K11(T) was a member of group 6 [Nielsen et al., FEMS Microbiol Lett 117 (1994), 61-66] (alkaliphiles) of the genus Bacillus. DNA-DNA hybridization revealed a low relatedness (14 %) of the isolate to its closest phylogenetic neighbour, Bacillus clausii. On the basis of phenotypic and chemotaxonomic characteristics, phylogenetic data and DNA-DNA relatedness data, it was concluded that K11(T) (=JCM 12663(T)=NCIMB 14023(T)) merits classification as the type strain of a novel species, for which the name Bacillus oshimensis sp. nov. is proposed.

Effect of DNA structure on the formation of collagen–DNA complex

Using various types of DNAs prepared from plasmid DNA, complete double-stranded DNA (ds.DNA) with linear and cyclic forms and double-stranded DNA coexisting with single-stranded DNA (ss.DNA), the structure and fibrillogenesis of the collagen-DNA complex were investigated by means of turbidity, transmission electron microscopy, and confocal laser-scanning microscopy. The rate of fibrillogenesis of the collagen-DNA complex significantly depends on the DNA structure. The structure of the fibrils formed in the complexes showed a marked difference between the ds.DNA and ss.DNA complexes with collagen. Spatial distribution of the DNA and collagen in the complexes suggests that the characteristic collagen-DNA interaction depends on the DNA forms.

Anoxybacillus voinovskiensis sp. nov., a moderately thermophilic bacterium from a hot spring in Kamchatka

A novel moderately thermophilic bacterium, strain TH13T, was isolated from a hot spring in Kamchatka. It was found to be a Gram-positive, facultative aerobe; the straight, non-motile rods grew at 30-64 degrees C (optimum 54 degrees C). The isolate was positive for catalase and oxidase tests and reduced nitrate to nitrite, but was negative for H2S production and growth in more than 3% NaCl (w/v). The isolate grew at pH 7-8, but not at pH values higher than 9. The DNA G+C content was 43.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that strain TH13T was a member of the genus Anoxybacillus. DNA-DNA hybridization revealed a low relatedness (less than 30.2%) between the isolate and its close phylogenetic neighbours Anoxybacillus pushchinoensis and Anoxybacillus flavithermus. On the basis of phenotypic characteristics, phylogenetic data and DNA-DNA hybridization data, it was concluded that the isolate merited classification as a novel species, for which the name Anoxybacillus voinovskiensis sp. nov. is proposed. The type strain of this species is TH13T (=NCIMB 13956T=JCM 12111T).

Influence of length on cytotoxicity of multi-walled carbon nanotubes against human acute monocytic leukemia cell line THP-1 in vitro and subcutaneous tissue of rats in vivo

Carbon nanotubes (CNTs) are single- or multi-cylindrical graphene structures that possess diameters of a few nanometers, while the length can be up to a few micrometers. These could have unusual toxicological properties, in that they share intermediate morphological characteristics of both fibers and nanoparticles. To date, no detailed study has been carried out to determine the effect of length on CNT cytotoxicity. In this paper, we investigated the activation of the human acute monocytic leukemia cell line THP-1 in vitro and the response in subcutaneous tissue in vivo to CNTs of different lengths. We used 220 nm and 825 nm-long CNT samples for testing, referred to as "220-CNTs" and "825-CNTs", respectively. 220-CNTs and 825-CNTs induced human monocytes in vitro, although the activity was significantly lower than that of microbial lipopeptide and lipopolysaccharide, and no activity appeared following variation in the length of CNTs. On the other hand, the degree of inflammatory response in subcutaneous tissue in rats around the 220-CNTs was slight in comparison with that around the 825-CNTs. These results indicated that the degree of inflammation around 825-CNTs was stronger than that around 220-CNTs since macrophages could envelop 220-CNTs more readily than 825-CNTs. However, no severe inflammatory response such as necrosis, degeneration or neutrophil infiltration in vivo was observed around both CNTs examined throughout the experimental period.

Biological behavior of hat-stacked carbon nanofibers in the subcutaneous tissue in rats

The tissue response to hat-stacked carbon nanofibers (H-CNFs) was evaluated. H-CNFs were implanted in the subcutaneous tissue of rats. Histological and ultrastructural investigations were carried out by transmission electron microscopy. Although many macrophages and foreign body giant cells were seen around H-CNFs, no severe inflammatory response such as necrosis was observed. Some H-CNFs were observed in lysosomal vacuoles of phagocytes. These results showed that H-CNFs were not strong prophlogistic substances and were englobed in vivo.

Caged multiwalled carbon nanotubes as the adsorbents for affinity-based elimination of ionic dyes

Multiwalled carbon nanotubes (MWCNTs) were used as the active elements for the first time for affinity-based elimination of ionic dyes. MWCNTs were encapsulated in cross-linked alginate (ALG) microvesicles using Ba2+ as the bridging ion. The Ba2+-alginate matrix constitutes a cage which holds the physically trapped MWCNTs. The cage carries negative charges on its surface. The cage restricts the access of anions of large molecular weight, such as humic acids, because of electrostatic repulsion. The cage also restricts the access of colloids of large size, because of size exclusion. Ionic dyes partition into the cage and then are captured by MWCNTs probably on the basis of van der Waals interactions occurring between the hexagonally arrayed carbon atoms in the graphite sheet of MWCNTs and the aromatic backbones of the dyes. As a result of these interactions the target species, namely, the ionic dyes, are eliminated efficiently by the MWCNTs of Ba2+-ALG/MWCNT composite adsorbents. The adsorptive capacities for elimination of acridine orange, ethidium bromide, eosin bluish, and orange G (the model species used for this study) were found as high as 0.44, 0.43, 0.33, and 0.31 micromol, respectively, for 1.0 mg of the caged MWCNTs. Adsorptive experiments with carbon nanofibers and activated carbons as the adsorbents were also performed. The MWCNT-based adsorbents provided the best capability for the affinity-based elimination of these targeted species. Biocompatibility experiments performed in vitro and in vivo provided promising results, suggesting potential applications of the caged MWCNTs in in situ environmental remediation.

Bacillus asahii sp. nov., a novel bacterium isolated from soil with the ability to deodorize the bad smell generated from short-chain fatty acids

In a screening campaign to isolate strains with the ability to remove the bad smell associated with animal faeces, strain MA001T was isolated from a soil sample obtained from Shizuoka prefecture, Japan. The isolate grew at pH 6–9 but not at pH 10. Cells were Gram-positive, straight rods with peritrichous flagella and produced ellipsoidal spores. The isolate was positive for catalase and oxidase tests but negative for indole production, deamination of phenylalanine and H2S production. The isolate did not produce acid from any carbohydrates tested and could not grow in more than 2 % NaCl. The DNA G+C content was 39·4 mol%. The cellular fatty acids profile consisted of significant amount of C15 branched-chain fatty acids, iso-C15 : 0 and anteiso-C15 : 0. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that strain MA001T was closely related to Bacillus simplex and Bacillus psychrosaccharolyticus. DNA–DNA hybridization revealed a low relatedness of the isolate to several phylogenetically close neighbours (less than 9 %). On the basis of the phenotypic characteristics observed, phylogenetic data based on 16S rRNA gene sequencing and DNA–DNA relatedness data, it is concluded that the isolate should be classified as representing a novel species, for which the name Bacillus asahii is proposed. The type strain is MA001T (=JCM 12112T=NCIMB 13969T).

Alkalibacterium psychrotolerans sp. nov., a psychrotolerant obligate alkaliphile that reduces an indigo dye

A psychrotolerant, obligately alkaliphilic bacterium, IDR2-2T, which is able to reduce indigo dye was isolated from a fermented polygonum indigo (Polygonum tinctorium Lour.) produced in Date, Hokkaido, using a traditional Japanese method. The isolate grew at pH 9–12 but not at pH 7–8. It was a Gram-positive, facultatively anaerobic, straight rod-shaped bacterium with peritrichous flagella. The isolate grew in 0–17 % (w/v) NaCl but not at NaCl concentrations higher than 18 % (w/v). Its major cellular fatty acids were C14 : 0, C16 : 0, C16 : 19c and C18 : 19c, and its DNA G+C content was 40·6 mol%. dl-lactic acid was the major end-product from d-glucose. No quinones could be detected. The peptidoglycan type was A4β, Orn–d-Glu. A phylogenetic analysis based on 16S rRNA gene sequence data indicated that strain IDR2-2T is a member of the genus Alkalibacterium. DNA–DNA hybridization revealed low relatedness (less than 25 %) between the isolate and two phylogenetically related strains, Alkalibacterium olivapovliticus and Marinilactibacillus psychrotolerans. On the basis of phenotypic characteristics, phylogenetic data and DNA–DNA relatedness data, the isolate merits classification as a novel species, for which the name Alkalibacterium psychrotolerans sp. nov. is proposed. The type strain is IDR2-2T (=JCM 12281T=NCIMB 13981T).

Exiguobacterium oxidotolerans sp. nov., a novel alkaliphile exhibiting high catalase activity

A novel alkaliphile was isolated from a drain of a fish processing plant. The isolate grew at a pH range of 7–10. Cells were Gram-positive, facultatively aerobic, motile rods with peritrichous flagella. Colonies were orange or yellow in colour. Catalase and oxidase reactions were positive. The isolate grew in 0–12 % NaCl but not above 15 % NaCl. Its cell extract exhibited 567 times higher catalase activity than an Escherichia coli cell extract. The major cellular fatty acids were iso-C13 : 0, anteiso-C13 : 0, iso-C15 : 0, iso-C16 : 0, iso-C17 : 0, anteiso-C17 : 0 and iso-C17 : 1. Its DNA G+C content was 46·7 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing and chemotaxonomic data indicated that strain T-2-2T is a member of the genus Exiguobacterium. DNA–DNA hybridization revealed a low relatedness of the isolate to several phylogenetic neighbours (less than 25 %). On the basis of phenotypic characteristics, phylogenetic data and DNA–DNA relatedness data, the isolate merits classification as a novel species, for which the name Exiguobacterium oxidotolerans sp. nov. is proposed. The type strain is T-2-2T (=JCM 12280T=NCIMB 13980T).