Multinuclear magnetic resonance studies on the chemical interaction of a self-etching adhesive with radicular and coronal human dentin

This study presents evidence at molecular level for the chemical interaction between human dentin from different tooth regions and a monomer with phosphate groups, incorporated in the formulation of a simplified adhesive system. Because dentin was observed as a powder, previous verification was obtained for an eventual collagen denaturation due to the grinding process. The presence of chemical bonds involving coronal (CD) or radicular dentin (RD) was investigated using multinuclear magnetic resonance (MR) techniques. Narrow signals were identified in the carbon magic angle spinning (MAS) spectra of CD and RD treated with the adhesive, which were assigned to methylenic groups in methacryloyloxydecyl dihydrogen phosphate (MDP) bound to hydroxyapatite Ca²⁺; ¹H spectra of the adhesive components and treated dentin, in ethanol, support this conclusion. ³¹P MAS spectra obtained from both dentin regions present additional shielding and broadening effects subsequent to application and photopolymerization of the adhesive, which were higher for CD. Multinuclear MR studies provided evidence for the interaction of the adhesive with dentin, which involves hydroxyapatite and is stronger for CD than for RD, but no direct proof was obtained on bonding to collagen.     

Divacancies in graphene and carbon nanotubes

Divacancies are among the most important defects that alter the charge transport properties of single-walled carbon nanotubes (SWNT), and we here study, using ab initio calculations, their properties. Two structures were investigated, one that has two pentagons side by side with an octagon (585) and another composed of three pentagons and three heptagons (555777). We investigate their stability as a function of tube diameter, and calculate their charge transport properties. The 585 defect is less stable in graphene due to two broken bonds in the pentagons. We estimate that the 555777 becomes more stable than the 585 for a diameter of about 40 A (53 A) for an armchair (zigzag) SWNTs, indicating that they will prevail in large diameter multiwalled carbon nanotubes and graphene ribbons.     

Biological evaluation of alginate-based hydrogels, with antimicrobial features by Ce(III) incorporation, as vehicles for a bone substitute

A novel hydrogel, based on an alginate/hyaluronate mixture and Ce(III) ions, with effective bioactive and antimicrobial ability was developed to be used as vehicle of a synthetic bone substitute producing an injectable substitute (IBS). Firstly, three different IBSs were prepared using three developed alginate-based hydrogels, the hydrogel Alg composed by alginate, the hydrogel Alg/Ch composed by an alginate/chitosan mixture and the hydrogel Alg/HA composed by an alginate/hyaluronate mixture. MG63 cells viability on the IBSs was evaluated, being observed a significantly higher cell viability on the Alg/HA_IBS at all time points, which indicates a better cell adaptation to the material, increasing their predisposition to produce extracellular matrix and thus allowing a better bone regeneration. Moreover, SEM analysis showed evident filopodia and a spreader shape of MG63 cells when seeded on Alg/HA_IBS. This way, based upon the in vitro results, the hydrogel Alg/HA was chosen to the in vivo study by subcutaneous implantation in an animal model, promoting a slight irritating tissue response and visible tissue repairing. The next step was to grant antimicrobial properties to the hydrogel that showed the best biological behavior by incorporation of Ce(III) ions into the Alg/HA, producing the hydrogel Alg/HA2. The antimicrobial activity of these hyaluronate-based hydrogels was evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Candida albicans. Results showed that Ce(III) ions can significantly enhance the hydrogel antimicrobial ability without compromising the osteoconductivity improvement promoted by the vehicle association to the synthetic bone substitute.     

Nanocomposites of poly(ε-caprolactone) doped with titanium species

Organic–inorganic hybrid nanocomposites were prepared via in situ sol–gel process. The organic phase is a biodegradable polymer, poly(ε-caprolactone) (PCL), while the tetrabutyl titanate (TBT, Ti(OBu)₄) was used as inorganic precursor. Synthesis parameters like acidity medium and precursor amount were investigated in order to assess their influence on hybrid properties. The obtained nanocomposites were characterised by thermal analysis, spectroscopic techniques, transmission electronic microscopy (TEM) and X-ray diffraction to gather information on the structure of the nanocomposites. Mechanical properties and biodegradability were also evaluated. A reaction mechanism based on Fourier transform infrared spectroscopy and NMR results was proposed using methyl acetate as model compound. TEM micrographs of the nanocomposites show a fine good nanoparticles dispersion. Acidic conditions and 10 wt% of precursor lead to a nanocomposite with higher mechanical properties and biodegradability than PCL.     

The Effects of pH on the Preparation of Alumina by Sol-Gel Process

ABSTRACT

This article describes the effects of pH on the preparation and properties of aluminas (A l ₂ O ₃) produced by the sol-gel colloidal method. The precursor, hexahydrated aluminum chloride, was subjected to peptization reactions giving rise to a viscous gel with amorphous characteristics. Calcination at temperatures about 1000°C caused this gel to transform into alumina products with different morphologies, such as powders, fibers, or porous ceramic bodies, depending on the process parameters adopted, such as the pH and the drying conditions.

These products were characterized according to their particle size distribution, thermogravimetry and differential thermal analysis (TG/DTA), and X-ray diffraction (XRD), and their morphologies were analyzed by scanning electron microscopy (SEM).     

Manufacture of bioactive peptide-rich concentrates from Whey: Characterization of pilot process

This work was focused on the manufacture, at pilot scale, of cow whey protein and peptide concentrates, using selective filtration techniques—associated with hydrolysis brought about by proteolytic enzymes from Cynara cardunculus aqueous extracts, using as (optimal) conditions an enzyme/substrate ratio of 1.6% v/v, a pH of 5.2, a temperature of 55 °C and an incubation time of 7 h. The profiles of proteins and peptides were assessed by liquid chromatography and electrophoresis; ca. 87% of α-lactalbumin was hydrolyzed, but essentially no degradation of β-lactoglobulin (β-Lg) was observed. A bioactive peptide concentrate, its fraction below 3 kDa and a β-Lg-rich fraction were obtained as final products, containing ca. 73, 43 and 91% w/w protein (on a total solid mass basis). All these fractions were low in lactose and salt, and their microbial loads were reduced. Said fractions are high added-value products, so they can be used as nutritional and functional ingredients—thus yielding an economically viable alternative for upgrade of whey.     

Novel copolymer for SiO2 nanoparticles dispersion

High performance polymers exhibiting multifunctional characteristics can be achieved by the introduction of inorganic nanoparticles like SiO₂ into the functional polymers. In the present work a copolymer epoxy poly(dimethylacrylamide) was synthesized to disperse the SiO₂ nanoparticles. The aim of the work is to develop a new method/process/material for the dispersion of nanoparticles and evaluating the performance of these composites. FT‐IR studies of the polymer adsorbed SiO₂ nanoparticles confirmed that the polymer molecules chain was anchored on the surface of the SiO₂ nanoparticles. The improved interfacial interaction between the particles and polymer enhanced the thermal properties of the composites. The results also show the newly synthesized polymer disperse the nanoparticles well as evidenced by SEM analysis, the uniformly dispersed SiO₂ nanoparticles in the polymer matrix and the particles almost remained in their original shape and size even after incorporation in to the polymer matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Protective effect of whey cheese matrix on probiotic strains exposed to simulated gastrointestinal conditions

A probiotic whey cheese added with Lactobacillus casei LAFTI®L26, Lactobacillus acidophilus LAFTI®L10 or Bifidobacterium animalis Bo was subject in vitro to sequential conditions that parallel the four major steps of digestion: mouth (artificial saliva), oesophagus-stomach (artificial gastric juice), duodenum (artificial intestinal juice) and ileum; its manufacture followed the traditional cheesemaking protocol of Portuguese Requeijão. MRS broth was inoculated in parallel as reference medium, to ascertain the protective effect of the whey cheese matrix itself upon those strains in every digestion step. Mouth conditions had an almost negligible effect upon all three strains, whereas oesophagus-stomach, duodenum and ileum conditions decreased the viable numbers of L. casei and L. acidophilus; in both systems, B. animalis suffered only slight decreases in viable numbers; and L. casei and L. acidophilus behaved likewise in MRS exposed to duodenum and ileum conditions. Whey cheese matrices thus appeared to protect the aforementioned three strains during transit throughout the simulated gastrointestinal system, so they are promising carriers of those probiotic bacteria.     

Optimization of fermentation conditions for production of the jabuticaba (Myrciaria cauliflora) spirit using the response surface methodology

The jabuticaba tree (Brazilian grape tree) is a tree native to Brazil that belongs to the Myrtaceae family. The jabuticaba fruit is used in some regions of Brazil to produce juices, jams, wine, and ice cream. In this work, the fermentation conditions (temperature and °Brix) for producing jabuticaba distillate were optimized using the response surface methodology (RSM). The optimal conditions for fermentation were found to be 20 °C and 22 °Brix. In repeated experiments to validate the model, experimental data exhibited good agreement with the predicted data. The distillate jabuticaba beverage showed a peculiar chemical composition with 20 volatile compounds that were identified and quantified. Isoamyl alcohols (2-methyl-1-butanol + 3-methyl-1-butanol) were the most abundant volatile compounds identified in jabuticaba spirit. Sensory analysis by tasters showed overall approval of jabuticaba distillate. In principal component analysis, when the beverage was evaluated by panelists under 24 y old tended to give favorable ratings of aroma and taste, as well as high overall scores. The group of panelists between the ages of 25 and 53 y old generally gave high marks for appearance in the principal component analysis. PRACTICAL APPLICATION: This study describes the study of fermentation conditions of jabuticaba pulp for production of jabuticaba spirit. Based on the results of this work, the proposed method can be an alternative for the use of the jabuticaba fruit, and may provide a new industrial outlet for this fruit.     

Two-step growth of HFCVD diamond films over large areas

This paper reports the results of a two-step hot filament chemical vapor deposition method to improve the quality of diamond films. Diamond films were deposited on a Si(100) substrate having an area of 45 cm² and a thickness of 60 μm, employing a HFCVD system. The first step is the growth of CVD diamond in the HFCVD reactor. In the second step, the samples were treated in a saturated solution of H₂SO₄:CrO₃ and rinsed in a (1:1) solution of H₂O₂:NH₄OH. After this procedure, a second diamond layer was deposited. The diamond films were analyzed by Raman scattering spectroscopy (RSS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The films showed a high degree of purity with a thickness of 60 μm, presenting uniform characteristics over a large area.