Bacterial cellulose-laponite clay nanocomposites

A novel material comprised of bacterial cellulose (BC) and Laponite clay with different inorganic organic ratios (m/m) was prepared by the contact of never-dried membranes of BC with a previous dispersion of clay particles in water. Field emission scanning electron microscopy (FE-SEM) data of composite materials revealed an effective adhesion of clay over the surface of BC membrane; inorganic particles also penetrate into the polymer bulk, with a significant change of the surface topography even at 5% of clay loading. As a consequence, the mechanical properties are deeply affected by the presence of clay, increasing the values of the Young modulus and the tensile strength. However the maximum strain is decreased when the clay content is increased in the composite in comparison to pristine BC. The main weight loss step of the composites is shifted towards higher temperatures compared to BC, indicating that the clay particles slightly protect the polymer from thermal and oxidative decomposition. (C) 2010 Elsevier Ltd. All rights reserved.

Application of 1-Allyl-3-(1-butyl)imidazolium Chloride in the Synthesis of Cellulose Esters: Properties of the Ionic Liquid, and Comparison with Other Solvents

The ionic liquid (IL), 1-allyl-3-(1-butyl)imidazolium chloride (AlBuImCl), has been synthesized and its properties determined. Increase in the temperature increased its conductivity and decreased its density, polarity, and viscosity. Microcrystalline cellulose (MCC), dissolves in thisIL by heating at 80 degrees C; this did not affect its degree of polymerization, decreased its index of crystallinity (Ic), and changed in morphology after regeneration. Convenient acylation of MCC was achieved by using 50% excess anhydride at 80 degrees C, for 24 or 48 h for acetic and butyric anhydride, respectively. The composition of the mixed esters depended on the initial ratio of the anhydrides, and their order of addition.

Use of checkerboard DNA-DNA hybridization to evaluate the internal contamination of dental implants and comparison of bacterial leakage with cast or pre-machined abutments

To evaluate the checkerboard DNA-DNA hybridization method for detection and quantitation of bacteria from the internal parts of dental implants and to compare bacterial leakage from implants connected either to cast or to pre-machined abutments. Nine plastic abutments cast in a Ni-Cr alloy and nine pre-machined Co-Cr alloy abutments with plastic sleeves cast in Ni-Cr were connected to Branemark-compatible implants. A group of nine implants was used as control. The implants were inoculated with 3 mu l of a solution containing 10(8) cells/ml of Streptococcus sobrinus. Bacterial samples were immediately collected from the control implants while assemblies were completely immersed in 5 ml of sterile Tripty Soy Broth (TSB) medium. After 14 days of anaerobic incubation, occurrence of leakage at the implant-abutment interface was evaluated by assessing contamination of the TSB medium. Internal contamination of the implants was evaluated with the checkerboard DNA-DNA hybridization method. DNA-DNA hybridization was sensitive enough to detect and quantify the microorganism from the internal parts of the implants. No differences in leakage and in internal contamination were found between cast and pre-machined abutments. Bacterial scores in the control group were significantly higher than in the other groups (P < 0.05). Bacterial leakage through the implant-abutment interface does not significantly differ when cast or pre-machined abutments are used. The checkerboard DNA-DNA hybridization technique is suitable for the evaluation of the internal contamination of dental implants although further studies are necessary to validate the use of computational methods for the improvement of the test accuracy. To cite this article:do Nascimento C, Barbosa RES, Issa JPM, Watanabe E, Ito IY, Albuquerque Junior RF. Use of checkerboard DNA-DNA hybridization to evaluate the internal contamination of dental implants and comparison of bacterial leakage with cast or pre-machined abutments.Clin. Oral Impl. Res. 20, 2009; 571-577.doi: 10.1111/j.1600-0501.2008.01663.x.

Bacterial leakage along the implant-abutment interface of premachined or cast components

In recent clinical studies, contamination of the inner parts of dental implants through bacterial penetration along the implant components has been observed. The aim of the present in-vitro study was to investigate leakage of Fusobacterium. nucleatum through the interface between implants and premachined or cast abutments. Both premachined (n = 10) and cast (n = 10) implant abutment assemblies were inoculated with 3.0 mu L of microbial inoculum. The assemblies were completely immersed in 5.0 mL of tryptic soy broth culture medium to observe leakage at the implant-abutment interface after 14 days of anaerobic incubation. Bacterial growth in the medium, indicative of microbial leakage, was found only in 1 out of 9 samples (11.1%) in each group. Both premachined and cast abutments connected to external hexagonal implants provide low percentages of bacterial leakage through the interface in in vitro unloaded conditions if the manufacturer`s instructions and casting procedures are properly followed.

Seasonal patterns of viral and bacterial infections among children hospitalized with community-acquired pneumonia in a tropical region

Community-acquired pneumonia (CAP) is a common cause of morbidity among children. Evidence on seasonality, especially on the frequency of viral and bacterial causative agents is scarce; such information may be useful in an era of changing climate conditions worldwide. To analyze the frequency of distinct infections, meteorological indicators and seasons in children hospitalized for CAP in Salvador, Brazil, nasopharyngeal aspirate and blood were collected from 184 patients aged < 5 y over a 21-month period. Fourteen microbes were investigated and 144 (78%) cases had the aetiology established. Significant differences were found in air temperature between spring and summer (p = 0.02) or winter (p < 0.001), summer and fall (p = 0.007) or winter (p < 0.001), fall and winter (p = 0.002), and on precipitation between spring and fall (p = 0.01). Correlations were found between: overall viral infections and relative humidity (p = 0.006; r = 0.6) or precipitation (p = 0.03; r = 0.5), parainfluenza and precipitation (p = 0.02; r = -0.5), respiratory syncytial virus (RSV) and air temperature (p = 0.048; r = -0.4) or precipitation (p = 0.045; r = 0.4), adenovirus and precipitation (p = 0.02; r = 0.5), pneumococcus and air temperature (p = 0.04; r = -0.4), and Chlamydia trachomatis and relative humidity (p = 0.02; r = -0.5). The frequency of parainfluenza infection was highest during spring (32.1%; p = 0.005) and that of RSV infection was highest in the fall (36.4%; p < 0.001). Correlations at regular strength were found between several microbes and meteorological indicators. Parainfluenza and RSV presented marked seasonal patterns.

Exploring Bacterial Diversity of Endodontic Microbiota by Cloning and Sequencing 16S rRNA

Introduction: The characterization of microbial communities infecting the endodontic system in each clinical condition may help on the establishment of a correct prognosis and distinct strategies of treatment. The purpose of this study was to determine the bacterial diversity in primary endodontic infections by 16S ribosomal-RNA (rRNA) sequence analysis. Methods: Samples from root canals of untreated asymptomatic teeth (n = 12) exhibiting periapical lesions were obtained, 165 rRNA bacterial genomic libraries were constructed and sequenced, and bacterial diversity was estimated. Results: A total of 489 clones were analyzed (mean, 40.7 +/- 8.0 clones per sample). Seventy phylotypes were identified of which six were novel phylotypes belonging to the family Ruminococcaceae. The mean number of taxa per canal was 10.0, ranging from 3 to 21 per sample; 65.7% of the cloned sequences represented phylotypes for which no cultivated isolates have been reported. The most prevalent taxa were Atopobium rimae (50.0%), Dialister invisus, Pre-votella oris, Pseudoramibacter alactolyticus, and Tannerella forsythia (33.3%). Conclusions: Although several key species predominate in endodontic samples of asymptomatic cases with periapical lesions, the primary endodontic infection is characterized by a wide bacterial diversity, which is mostly represented by members of the phylum Firmicutes belonging to the class Clostridia followed by the phylum Bacteroidetes. (J Ended 2011;37:922-926)

The pst operon of enteropathogenic Escherichia coli enhances bacterial adherence to epithelial cells

Enteropathogenic Escherichia coli (EPEC) adheres in vivo and in vitro to epithelial cells. Two main adhesins, the bundle-forming pilus and intimin, encoded by the Up operon and eae, respectively, are responsible for the localized and the intimate adherence phenotypes. Deletion of the pst operon of EPEC abolishes the transport of inorganic phosphate through the phosphate-specific transport system and causes the constitutive expression of the PHO regulon genes. In the absence of pst there is a decrease in the expression of the main EPEC adhesins and a reduction in bacterial adherence to epithelial cells in vitro. This effect is not related to PHO constitutivity, because a Delta pst phoB double mutant that is defective in the transcription of the PHO genes also displayed low levels of adherence and expression of adhesins. Likewise, a PHO-constitutive phoR mutation did not affect bacterial adherence. The expression of the per operon, which encodes the Up and ler regulators PerA and PerC, is also negatively affected by the pst deletion. Overall, the data presented here demonstrate that the pst operon of EPEC plays a positive role in the bacterial adherence mechanism by increasing the expression of perA and perC and consequently the transcription of bfp and eae.

Phylogenetic Validation of the Genera Angomonas and Strigomonas of Trypanosomatids Harboring Bacterial Endosymbionts with the Description of New Species of Trypanosomatids and of Proteobacterial Symbionts

We comparatively examined the nutritional, molecular and optical and electron microscopical characteristics of reference species and new isolates of trypanosomatids harboring bacterial endosymbionts. Sequencing of the V7V8 region of the small subunit of the ribosomal RNA (SSU rRNA) gene distinguished six major genotypes among the 13 isolates examined. The entire sequences of the SSU rRNA and glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) genes were obtained for phylogenetic analyses. In the resulting phylogenetic trees, the symbiont-harboring species clustered as a major clade comprising two subclades that corresponded to the proposed genera Angomonas and Strigomonas. The genus Angomonas comprised 10 flagellates including former Crithidia deanei and C. desouzai plus a new species. The genus Strigomonas included former Crithidia oncopelti and Blastocrithidia cuiicis plus a new species. Sequences from the internal transcribed spacer of ribosomal DNA (ITS rDNA) and size polymorphism of kinetoplast DNA (kDNA) minicircles revealed considerable genetic heterogeneity within the genera Angomonas and Strigomonas. Phylogenetic analyses based on 16S rDNA and ITS rDNA sequences demonstrated that all of the endosymbionts belonged to the Betaproteobacteria and revealed three new species. The congruence of the phylogenetic trees of trypanosomatids and their symbionts support a co-divergent host-symbiont evolutionary history. (C) 2011 Elsevier GmbH. All rights reserved.

Stability and interface properties of thin cellulose ester films adsorbed from acetone and ethyl acetate solutions

Stability and interface properties of cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) films adsorbed from acetone or ethyl acetate onto Si wafers have been investigated by means of contact angle measurements and atomic force microscopy (AFM). Surface energy (gamma(total)(S)) values determined for CAP adsorbed from acetone are larger than those from ethyl acetate. In the case of CAB films adsorbed from ethyl acetate and acetone were similar. Dewetting was observed by AFM only for CAP films prepared from ethyl acetate. Positive values of effective Hamaker constant (A(eff)) were found only for CAP prepared from ethyl acetate, corroborating with dewetting phenomena observed by AFM. Oil the contrary, negative values of A(eff) were determined for CAP and CAB prepared from acetone and for CAB prepared from ethyl acetate, Corroborating with experimental observations. Sum frequency generation (SFG) vibrational spectra indicated that CAP and CAB films prepared from ethyl acetate present more alkyl groups oriented perpendicularly to the polymer-air interface than those films prepared from acetone. Such preferential orientation corroborates with macroscopic contact angle measurements. Moreover, SFG spectra showed that acetone hinds strongly to Si wafers, creating a new surface for CAP and CAB films. (C) 2008 Elsevier Inc. All rights reserved.

A Morphological View of the Sodium 4,4 `-Distyrylbiphenyl Sulfonate Fluorescent Brightness Distribution on Regenerated Cellulose Fibers

Evidence of the sorption of the whitening agent sodium 4,4`-distyrylbiphenyl sulfonate in the presence of the anionic surfactant sodium dodecylsulfate or the cationic surfactant dodecyl trimethyl ammonium chloride on regenerated cellulose fibers is given by several microscopy techniques. Scanning electron microscopy provided images of the cylindrical fibers with dimensions of 3.5 cm (length) and 13.3 mu m (thickness), with empty cores of 1 mu m diameter and a smooth surface. Atomic force microscopy showed a fiber surface with disoriented nanometric domains using both tapping-mode height and phase image modes. Atomic force microscopy also showed that the whitening agent and surfactant molecules were sorbed onto the fiber surface, in agreement with the adsolubilization sorption model. Transmission electron microscopy showed fibers with nanometric parallel cylinders, surrounded by holes where the fluorescent whitening molecules accumulated. On the basis of these techniques, we conclude that the sorption process occurs preferentially on the fiber surface in contact with the water solution, and under saturated conditions, the whitening agent penetrates into the pores and are simultaneously sorbed on the pore walls bulk, forming molecular aggregates. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 2321-2327, 2010

Highly Stable, Edible Cellulose Films Incorporating Chitosan Nanoparticles

The need for biodegradable polymers for packaging has fostered the development of novel, biodegradable polymeric materials from natural sources, as an alternative to reduce amount of waste and environmental impacts. The present investigation involves the synthesis of chitosan nanoparticles-carboxymethylcellulose films, in view of their increasing areas of application in packaging industry. The entire process consists of 2-steps including chitosan nanoparticles preparation and their incorporation in carboxymethylcellulose films. Uniform and stable particles were obtained with 3 different chitosan concentrations. The morphology of chitosan nanoparticles was tested by transmission electron microscopy, revealing the nanoparticles size in the range of 80 to 110 nm. The developed film chitosan nanoparticles-carboxymethylcellulose films were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis, solubility tests, and mechanical analysis. Improvement of thermal and mechanical properties were observed in films containing nanoparticles, with the best results occurring upon addition of nanoparticles with 110 nm size in carboxymethylcellulose films. Practical Application Carboxymethylcellulose films containing chitosan nanoparticles synthesized and characterized in this article could be a potential material for food and beverage packaging applications products due to the increase mechanical properties and high stability. The potential application of the nanocomposites prepared would be in packaging industry to extend the shelf life of products.

Bacterial Community Composition in Brazilian Anthrosols and Adjacent Soils Characterized Using Culturing and Molecular Identification

Microbial community composition was examined in two soil types, Anthrosols and adjacent soils, sampled from three locations in the Brazilian Amazon. The Anthrosols, also known as Amazonian dark earths, are highly fertile soils that are a legacy of pre-Columbian settlement. Both Anthrosols and adjacent soils are derived from the same parent material and subject to the same environmental conditions, including rainfall and temperature; however, the Anthrosols contain high levels of charcoal-like black carbon from which they derive their dark color. The Anthrosols typically have higher cation exchange capacity, higher pH, and higher phosphorus and calcium contents. We used culture media prepared from soil extracts to isolate bacteria unique to the two soil types and then sequenced their 16S rRNA genes to determine their phylogenetic placement. Higher numbers of culturable bacteria, by over two orders of magnitude at the deepest sampling depths, were counted in the Anthrosols. Sequences of bacteria isolated on soil extract media yielded five possible new bacterial families. Also, a higher number of families in the bacteria were represented by isolates from the deeper soil depths in the Anthrosols. Higher bacterial populations and a greater diversity of isolates were found in all of the Anthrosols, to a depth of up to 1 m, compared to adjacent soils located within 50-500 m of their associated Anthrosols. Compared to standard culture media, soil extract media revealed diverse soil microbial populations adapted to the unique biochemistry and physiological ecology of these Anthrosols.

Characteristics of thin cellulose ester films spin-coated from acetone and ethyl acetate solutions

Spin-coated films of cellulose acetate (CA), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB) and carboxymethylcellulose acetate butyrate (CMCAB) have been characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The films were spin-coated onto silicon wafers, a polar surface. Mean thickness values were determined by means of ellipsometry and AFM as a function of polymer concentration in solutions prepared either in acetone or in ethyl acetate (EA), both are good solvents for the cellulose esters. The results were discussed in the light of solvent evaporation rate and interaction energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology, surface roughness and surface wettability were also investigated.

Microwave-Assisted Derivatization of Cellulose in an Ionic Liquid: An Efficient, Expedient Synthesis of Simple and Mixed Carboxylic Esters

Microwave (MW)-assisted cellulose dissolution in ionic liquids (ILs) has routinely led either to incomplete biopolymer solubilization, or its degradation. We show that these problems can be avoided by use of low-energy MW heating, coupled with efficient stirring. Dissolution of microcrystalline cellulose in the IL 1-allyl-3-methylimidazolium chloride has been achieved without changing its degree of polymerization; regenerated cellulose showed pronounced changes in its index of crystallinity, surface area, and morphology. MW-assisted functionalization of MCC by ethanoic, propanoic, butanoic, pentanoic, and hexanoic anhydrides has been studied. Compared with conventional heating, MW irradiation has resulted in considerable decrease in dissolution and reaction times. The value of the degree of substitution (DS) was found to be DS(ethanoate) > DS(propanoate) > DS(butanoate). The values of DS(pentanoate) and DS(hexanoate) were found to be slightly higher than DS(ethanoate). This surprising dependence on the chain length of the acylating agent has been reported before, but not rationalized. On the basis of the rate constants and activation parameters of the hydrolysis of ethanoic, butanoic, and hexanoic anhydrides in aqueous acetonitrile (a model acyl transfer reaction), we suggest that this result may be attributed to the balance between two opposing effects, namely, steric crowding and (cooperative) hydrophobic interactions between the anhydride and the cellulosic surface, whose lipophilicity has increased, due to its partial acylation. Four ethanoate-based mixed esters were synthesized by the reaction with a mixture of the two anhydrides; the ethanoate moiety predominated in all products. The DS is reproducible and the IL is easily recycled. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 134-143, 2010

Cellulose swelling by aprotic and protic solvents: What are the similarities and differences?

The swelling of microcrystalline, native and mercerized cotton and eucalyptus celluloses by 16 aprotic solvents was investigated. The number of moles of solvent/anhydroglucose unit, nSw, correlates well with solvent molar volume, basicity and dipolarity/polarizability. Swelling is sensitive to cellulose crystallite size, surface area and the presence of its chains in parallel or anti-parallel arrangements. Use of solvatochromic parameters is a superior alternative to the use of other descriptors, such as Hildebrand`s solubility parameters and Gutmann`s donor numbers. The calculated nSw for 28 protic and aprotic solvents correlated well with their experimental counterparts, although hydrogen bond donation by the solvent was not included.