Synthesis and biocompatibility of an experimental glass ionomer cement prepared by a non-hydrolytic sol-gel method

The aims of this study were to demonstrate the synthesis of an experimental glass ionomer cement (GIC) by the non-hydrolytic sol-gel method and to evaluate its biocompatibility in comparison to a conventional glass ionomer cement (Vidrion R). Four polyethylene tubes containing the tested cements were implanted in the dorsal region of 15 rats, as follows: GI - experimental GIC and GII - conventional GIC. The external tube walls was considered the control group (CG). The rats were sacrificed 7, 21 and 42 days after implant placement for histopathological analysis. A four-point (I-IV) scoring system was used to graduate the inflammatory reaction. Regarding the experimental GIC sintherization, thermogravimetric and x-ray diffraction analysis demonstrated vitreous material formation at 110oC by the sol-gel method. For biocompatibility test, results showed a moderate chronic inflammatory reaction for GI (III), severe for GII (IV) and mild for CG (II) at 7 days. After 21 days, GI presented a mild reaction (II); GII, moderate (III) and CG, mild (II). At 42 days, GI showed a mild/absent inflammatory reaction (II to I), similar to GII (II to I). CG presented absence of chronic inflammatory reaction (I). It was concluded that the experimental GIC presented mild/absent tissue reaction after 42 days, being biocompatible when tested in the connective tissue of rats.

In vitro effect of low intensity laser on the cytotoxicity produced by substances released by bleaching gel

This in vitro study aimed to analyze the effect of different parameters of phototherapy with low intensity laser on the viability of human dental pulp fibroblasts under the effect of substances released by bleaching gel. Cells were seeded into 96 wells plates (1 x 10³ cells/well) and placed in contact with culture medium conditioned by a 35 % hydrogen peroxide bleaching gel for 40 minutes, simulating the clinical condition of the in-office bleaching treatment. Cells cultured in ideal growth conditions served as positive control group (PC), and the cells grown in conditioned medium and non-irradiated served as negative control group (NC). Cells grown in conditioned medium were submitted to a single irradiation with a diode laser (40 mW, 0.04 cm²) emitting at visible red (660 nm; RL) or near infrared (780 nm; NIR) using punctual technique, in contact mode and energy densities of 4, 6 or 10 J/cm². The cell viability was analyzed through the MTT reduction assay immediately and 24 hours after the irradiation. The data was compared by ANOVA followed by the Tukey's test (p < 0.05). The cell viability increased significantly in 24 hours within each group. The PC presented cell viability significantly higher than NC in both experimental times. Only the NIR/10 J/cm² group presented cell viability similar to that of PC in 24 hours. The phototherapy with low intensity laser in defined parameters is able to compensate the cytotoxic effects of substances released by 35 % hydrogen peroxide bleaching gel.

Analysis of the periodontal status of patients with mandibular-bonded retainers

PURPOSE: This clinical study evaluated the periodontal status of patients with bonded retainers as compared to a non-treated control group. METHODS: Forty dental students were included in the sample and divided into the following two groups: 1) a test group of 20 subjects that, after orthodontic treatment, have been bonded retainer users for at least 2 years and 2) a control group of 20 patients that never experienced orthodontic treatment nor used any bonded retainer. The region associated with the retainer in the test group and the lower canine-to-canine region in the control group were examined according to the following clinical parameters: plaque index (PI), bleeding on probing (BOP), gingival recession (GR), clinical attachment level (CAL) and probing depth (PD). RESULTS: No differences were observed for GR or BOP (P>0.05). In contrast, the test group showed higher values of CAL and PD at proximal sites when compared to controls (P<0.05). In addition, IP was significantly increased at buccal and lingual sites (P<0.05). CONCLUSION: The placement of orthodontic bonded retainers negatively affected periodontal health, resulting in increased PI, PD and CAL.

Two-dimensional gel electrophoretic protein profile analysis during seed development of Ocotea catharinensis: a recalcitrant seed species

The aim of the present work was to characterize changes in the protein profile throughout seed development in O. catharinensis, a recalcitrant species, by two-dimensional gel electrophoresis. Protein extraction was undertaken by using a thiourea/urea buffer, followed by a precipitation step with 10% TCA. Comparative analysis during seed development showed that a large number of proteins were exclusively detected in each developmental stage. The cotyledonary stage, which represents the transition phase between embryogenesis and the beginning of metabolism related to maturation, presents the highest number of stage-specific spots. Protein identification, through MS/MS analysis, resulted in the identification of proteins mainly related to oxidative metabolism and storage synthesis. These findings contribute to a better understanding of protein metabolism during seed development in recalcitrant seeds, besides providing information on established markers that could be useful in defining and improving somatic embryogenesis protocols, besides monitoring the development of somatic embryos in this species.

Obtaining high purity silica from rice hulls

Many routes for extracting silica from rice hulls are based on direct calcining. These methods, though, often produce silica contaminated with inorganic impurities. This work presents the study of a strategy for obtaining silica from rice hulls with a purity level adequate for applications in electronics. The technique is based on two leaching steps, using respectively aqua regia and Piranha solutions, which extract the organic matrix and inorganic impurities. The material was characterized by Fourier-transform infrared spectroscopy (FTIR), powder x-ray diffraction (XRD), x-ray fluorescence (XRF), scanning electron microscopy (SEM), particle size analysis by laser diffraction (LPSA) and thermal analysis.

Silica-based cationic bilayers as immunoadjuvants

Background: Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design. Results: Firstly, the silica/DODAB assembly was characterized at 1 mM NaCl, pH 6.3 or 5 mM Tris. HCl, pH 7.4 and 0.1 mg/ml silica over a range of DODAB concentrations (0.001-1 mM) by means of dynamic light scattering for particle sizing and zeta-potential analysis. 0.05 mM DODAB is enough to produce cationic bilayer-covered particles with good colloid stability. Secondly, conditions for maximal adsorption of bovine serum albumin (BSA) or a recombinant, heat-shock protein from Mycobacterium leprae (18 kDa-hsp) onto DODAB-covered or onto bare silica were determined. At maximal antigen adsorption, cellular immune responses in vivo from delayed-type hypersensitivity reactions determined by foot-pad swelling tests (DTH) and cytokines analysis evidenced the superior performance of the silica/DODAB adjuvant as compared to alum or antigens alone whereas humoral response from IgG in serum was equal to the one elicited by alum as adjuvant. Conclusion: Cationized silica is a biocompatible, inexpensive, easily prepared and possibly general immunoadjuvant for antigen presentation which displays higher colloid stability than alum, better performance regarding cellular immune responses and employs very low, micromolar doses of cationic and toxic synthetic lipid.

Iridium(III)-surfactant complex immobilized in mesoporous silica via templated synthesis: a new route to optical materials

In this work we report the preparation of a new blue-emitting material based on the templated synthesis of mesoporous silica (MCM-41) using micellar solutions of the newly synthesized monocationic metallosurfactant complex bis[1-benzyl-4-(2,4-difluorophenyl)-1H-1,2,3-triazole](4,4'-diheptadecyl-2,2'- bipyridine)-iridium(III) chloride in hexadecyl-trimethyl-ammonium bromide (CTAB). Under ambient conditions, significant increases in excited state lifetime and quantum yield values (up to 45%), were obtained for the solid materials in comparison to the corresponding micellar solutions. Solid state (1)H and (19)F NMR spectroscopies were successfully employed for quantifying the luminophore content in terms of Ir-surfactant to CTAB and Ir-surfactant to silica ratios.

Enhancement of hematoporphyrin IX potential for photodynamic therapy by entrapment in silica nanospheres

The entrapment of hematoporphyrin IX (Hp IX) in silica by means of a microemulsion resulted in silica spheres of 33 +/- 6 nm. The small size, narrow size distribution and lack of aggregation maintain Hp IX silica nanospheres stable in aqueous solutions for long periods and permit a detailed study of the entrapped drug by different techniques. Hp IX entrapped in the silica matrix is accessed by oxygen and upon irradiation generates singlet oxygen which diffuses very efficiently to the outside solution. The Hp IX entrapped in the silica matrix is also reached by iron(II) ions, which causes quenching of the porphyrin fluorescence emission. The silica matrix also provides extra protection to the photosensitizer against interaction with BSA and ascorbic acid, which are known to cause suppression of singlet oxygen generation by the Hp IX free in solution. Therefore, the incorporation of Hp IX molecules into silica nanospheres increased the potential of the photosensitizer to perform photodynamic therapy.

Characterization of dynamic solid phase DNA extraction from blood with magnetically controlled silica beads

A novel solid phase extraction technique is described where DNA is bound and eluted from magnetic silica beads in a manner where efficiency is dependent on the magnetic manipulation of the beads and not on the flow of solution through a packed bed. The utility of this technique in the isolation of reasonably pure, PCR-amplifiable DNA from complex samples is shown by isolating DNA from whole human blood, and subsequently amplifying a fragment of the beta-globin gene. By effectively controlling the movement of the solid phase in the presence of a static sample, the issues associated with reproducibly packing a solid phase in a microchannel and maintaining consistent flow rates are eliminated. The technique described here is rapid, simple, and efficient, allowing for recovery of more than 60% of DNA from 0.6 mu L of blood at a concentration which is suitable for PCR amplification. In addition, the technique presented here requires inexpensive, common laboratory equipment, making it easily adopted for both clinical point-of-care applications and on-site forensic sample analysis.

Disparity between Multilocus Enzyme Electrophoresis, Microsatellite Markers and Pulsed-Field Gel Electrophoresis in epidemiological tracking of Candida albicans

Various molecular systems are available for epidemiological, genetic, evolutionary, taxonomic and systematic studies of innumerable fungal infections, especially those caused by the opportunistic pathogen C. albicans. A total of 75 independent oral isolates were selected in order to compare Multilocus Enzyme Electrophoresis (MLEE), Electrophoretic Karyotyping (EK) and Microsatellite Markers (Simple Sequence Repeats - SSRs), in their abilities to differentiate and group C. albicans isolates (discriminatory power), and also, to evaluate the concordance and similarity of the groups of strains determined by cluster analysis for each fingerprinting method. Isoenzyme typing was performed using eleven enzyme systems: Adh, Sdh, M1p, Mdh, Idh, Gdh, G6pdh, Asd, Cat, Po, and Lap (data previously published). The EK method consisted of chromosomal DNA separation by pulsed-field gel electrophoresis using a CHEF system. The microsatellite markers were investigated by PCR using three polymorphic loci: EF3, CDC3, and HIS3. Dendrograms were generated by the SAHN method and UPGMA algorithm based on similarity matrices (S(SM)). The discriminatory power of the three methods was over 95%, however a paired analysis among them showed a parity of 19.7-22.4% in the identification of strains. Weak correlation was also observed among the genetic similarity matrices (S(SM)(MLEE) x S(SM)(EK) x S(SM)(SSRs)). Clustering analyses showed a mean of 9 +/- 12.4 isolates per cluster (3.8 +/- 8 isolates/taxon) for MLEE, 6.2 +/- 4.9 isolates per cluster (4 +/- 4.5 isolates/taxon) for SSRs, and 4.1 +/- 2.3 isolates per cluster (2.6 +/- 2.3 isolates/taxon) for EK. A total of 45 (13%), 39(11.2%), 5 (1.4%) and 3 (0.9%) clusters pairs from 347 showed similarity (Si) of 0.1-10%, 10.1-20%, 20.1-30% and 30.1-40%, respectively. Clinical and molecular epidemiological correlation involving the opportunistic pathogen C. albicans may be attributed dependently of each method of genotyping (i.e., MLEE, EK, and SSRs) supplemented with similarity and grouping analysis. Therefore, the use of genotyping systems that give results which offer minimum disparity, or the combination of the results of these systems, can provide greater security and consistency in the determination of strains and their genetic relationships. (C) 2010 Elsevier B.V. All rights reserved.

Pseudomonas fluorescens lipase immobilization on polysiloxane-polyvinyl alcohol composite chemically modified with epichlorohydrin

The technique based on sol-gel approach was used to generate silica matrices derivatives by hydrolysis of silane compounds. The present work evaluates a hybrid matrix obtained with tetraethoxysilane (TEOS) and polyvinyl alcohol (PVA) on the immobilization yield of lipase from Pseudomonas fluorescens. The resulting polysiloxane-polyvinyl alcohol (POS-PVA) matrix combines the property of PVA as a suitable polymer to retain proteins with an excellent optical, thermal and chemical stability of the host silicon oxide matrix. Aiming to render adequate functional groups to the covalent binding with the enzyme the POS-PVA matrix was chemically modified using epichlorohydrin. The results were compared with immobilized derivative on POS-PVA activated with glutaraldehyde. Immobilization yield based on the recovered lipase activity depended on the activating agent and the highest efficiency (32%) was attained when lipase was immobilized on POS-PVA activated with epichlorohydrin, which, probably, provided more linkage points for the covalent bind of the enzyme on the support. This was confirmed by determining the morphological properties using different techniques as X-ray diffraction and scanning electron microscopy (SEM). Comparative studies were carried out to attain optimal activities for free lipase and immobilized systems. For this purpose, a central composite experimental design with different combinations of pH and temperature was performed. Enzymatic hydrolysis with the immobilized enzyme in the framework of the Michaelis-Menten mechanism was also reported. Under optimum conditions, the immobilized derivative on POS-PVA activated with epichlorohydrin showed to have more affinity for the substrate in the hydrolysis of olive oil, with a Michaelis-Menten constant value (K-m) of 293 mM, compared to the value of 401 mM obtained for the immobilized lipase on support activated with glutaraldehyde. Data generated by DSC showed that both immobilized derivatives have similar thermal stabilities. (C) 2007 Elsevier B.V. All rights reserved.

Response surface methodology as an approach to determine optimal activities of lipase entrapped in sol-gel matrix using different vegetable oils

The conditions for maximization of the enzymatic activity of lipase entrapped in sol-gel matrix were determined for different vegetable oils using an experimental design. The effects of pH, temperature, and biocatalyst loading on lipase activity were verified using a central composite experimental design leading to a set of 13 assays and the surface response analysis. For canola oil and entrapped lipase, statistical analyses showed significant effects for pH and temperature and also the interactions between pH and temperature and temperature and biocatalyst loading. For the olive oil and entrapped lipase, it was verified that the pH was the only variable statistically significant. This study demonstrated that response surface analysis is a methodology appropriate for the maximization of the percentage of hydrolysis, as a function of pH, temperature, and lipase loading.

Glulam beams reinforced with FRP externally-bonded: theoretical and experimental evaluation

The glued- laminated lumber (glulam) technique is an efficient process for the rational use of wood. Fiber-reinforced polymer (FRPs) associated with glulam beams provide significant improvements in strength and stiffness and alter the failure mode of these structural elements. In this context, this paper presents guidance for glulam beam production, an experimental analysis of glulam beams made of Pinus caribea var. hondurensis species without and with externally-bonded FRP and theoretical models to evaluate reinforced glulam beams (bending strength and stiffness). Concerning the bending strength of the beams, this paper aims only to analyze the limit state of ultimate strength in compression and tension. A specific disposal was used in order to avoid lateral buckling, once the tested beams have a higher ratio height-to-width. The results indicate the need of production control so as to guarantee a higher efficiency of the glulam beams. The FRP introduced in the tensile section of glulam beams resulted in improvements on their bending strength and stiffness due to the reinforcement thickness increase. During the beams testing, two failure stages were observed. The first was a tensile failure on the sheet positioned under the reinforcement layer, while the second occurred as a result of a preliminary compression yielding on the upper side of the lumber, followed by both a shear failure on the fiber-lumber interface and a tensile failure in wood. The model shows a good correlation between the experimental and estimated results.

A comparison between neodymium doped alumina samples obtained by Pechini and sol-gel methods using thermo-stimulated luminescence and SEM

Neodymium doped and undoped aluminum oxide samples were obtained using two different techniques: Pechini and sol-gel. Fine grained powders were produced using both procedures, which were analyzed using Scanning Electron Microscopy (SEM) and Thermo-Stimulated Luminescence (TSL). Results showed that neodymium ions incorporation is responsible for the creation of two new TSL peaks (125 and 265 degrees C) and, also, for the enhancement of the intrinsic TSL peak at 190 degrees C. An explanation was proposed for these observations. SEM gave the dimensions of the clusters produced by each method, showing that those obtained by Pechini are smaller than the ones produced by sol-gel; it can also explain the higher emission supplied by the first one. (C) 2010 Elsevier B.V. All rights reserved.

Finite element computational modeling of externally bonded CFRP composites flexural behavior in RC beams

This paper focuses on the flexural behavior of RC beams externally strengthened with Carbon Fiber Reinforced Polymers (CFRP) fabric. A non-linear finite element (FE) analysis strategy is proposed to support the beam flexural behavior experimental analysis. A development system (QUEBRA2D/FEMOOP programs) has been used to accomplish the numerical simulation. Appropriate constitutive models for concrete, rebars, CFRP and bond-slip interfaces have been implemented and adjusted to represent the composite system behavior. Interface and truss finite elements have been implemented (discrete and embedded approaches) for the numerical representation of rebars, interfaces and composites.