Thermoluminescence and optical absorption studies of natural grossular minerals

The optical absorption spectra of two samples of grossular have been measured at room temperature. An intense charge transfer band (UVCT) of iron extends to the visible and near infrared region. Some peaks associated to Fe3+ ions in tetrahedral and octahedral positions have been identified and their energy levels were computed. Mn2+ and Fe2+ ions are responsible with some bands and probably these ions occupy dodecahedral positions. No change in the intensity of optical absorption spectra were found after gamma dose, but only the 505 nm band decreases with irradiation. The OH spectra, consisting of OH overtones at 2750nm and asymmetric OH bands in the near infrared region were observed in the two samples. The heat treatment produces Fe2+ -> Fe3+ and Mn2+ -> Mn3+ by oxidation. This last was observed in sample II only. The thermally stimulated luminescence of both grossular samples has been investigated. Due to differences in iron and manganese concentration, not only a large difference has been observed in their optical absorption behavior, but also a striking difference in their thermoluminescent behavior. Actually, it is not clear whether other impurities such as Ti, Na and K that are present in quite different concentration in grossular I and II are also contributing to the thermoluminescenct properties of both samples. (C) 2008 Elsevier Ltd. All rights reserved.

Oxide surface modification: Synthesis and characterization of zirconia-coated alumina

Four aluminas were used as Supports for impregnation with a zirconium oxide with the aim to achieve a coating, without phase separation, between Support and modifier. The Supports were impregnated with different concentrations Of zirconium aqueous resin, obtained through the polymeric precursor method. After impregnation the samples were calcined and then characterized by XRD, which led to identification of crystalline zirconia in different concentrations from each support used. Using a simple geometric model the maximum amount Of Surface modifier Oxide required for the complete coating of a support with a layer of unit cells was estimated. According to this estimate, only the support should be identified below the limit proposed and crystalline zirconium oxide Should be identified above this limit when a complete coating is reached. The results obtained From XRD agree with the estimated values and to confirm the coating, the samples were also characterized by EDS/STEM, HRTEM, XPS, and XAS. The results showed that the zirconium oxide oil the Surface of alumina Support reached the coating in the limit of 15 Zr nm(-2), without the formation of the ZrO(2) phase. (c) 2009 Elsevier Inc. All rights reserved.

Thermal and structural properties of commercial dental resins light-cured with blue emitting diodes (LEDs)

We have investigated the thermal and structural properties of different commercial dental resins: Filtek(TM) Z-350, Grandio(A (R)), Tetric Ceram(A (R)), and TPH Spectrum(A (R)). The purpose of the present study was to evaluate quantitatively the photo-polymerization behavior and the effect of filler contents on the kinetic cures of the dental resins by using Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. We have successfully obtained the low and high glass transition T (g) values of the dental composite resins from DSC curves. It was also observed a good agreement between the both T (g) values, activation energies from thermal degradation, and the degree of conversion obtained for all samples. The results have shown that Tetric Ceram(A (R)) dental resin presented the higher T (g) values, activation energy of 215 +/- A 6 KJ mol(-1), and the higher degree of conversion (63%) when compared to the other resins studied herein.

The interaction of an antiparasitic peptide active against African Sleeping Sickness with cell membrane models

Zwitterionic peptides with trypanocidal activity are promising lead compounds for the treatment of African Sleeping Sickness, and have motivated research into the design of compounds capable of disrupting the protozoan membrane. In this study, we use the Langmuir monolayer technique to investigate the surface properties of an antiparasitic peptide, namely S-(2,4-dinitrophenyl)glutathione di-2-propyl ester, and its interaction with a model membrane comprising a phospholipid monolayer. The drug formed stable Langmuir monolayers. whose main feature was a phase transition accompanied by a negative surface elasticity. This was attributed to aggregation upon compression due to intermolecular bond associations of the molecules, inferred from surface pressure and surface potential isotherms. Brewster angle microscopy (BAM) images, infrared spectroscopy and dynamic elasticity measurements. When co-spread with dipalmitoyl phosphatidyl choline (DPPC). the drug affected both the surface pressure and the monolayer morphology, even at high surface pressures and with low amounts of the drug. The results were interpreted by assuming a repulsive, cooperative interaction between the drug and DPPC molecules. Such repulsive interaction and the large changes in fluidity arising from drug aggregation may be related to the disruption of the membrane, which is key for the parasite killing property. (C) 2009 Elsevier B.V. All rights reserved.

Cholesterol Mediates Chitosan Activity on Phospholipid Monolayers and Langmuir-Blodgett Films

The polysaccharide chitosan has been largely used in many biological applications as a fat and cholesterol reducer, bactericide agent, and wound healing material. While the efficacy for some of such uses is proven, little is known about the molecular-level interactions involved in these applications. In this study, we employ mixed Langmuir and Langmuir-Blodgett (LB) films of negatively charged dimyristoyl phosphatidic acid (DMPA) anti cholesterol as cell membrane models to investigate the role of cholesterol in the molecular-level action of chitosan. Chitosan does not remove cholesterol froth the monolayer. The interaction with chitosan tends to expand the DMPA monolayer due to its interpenetration within the film. On the other hand, cholesterol induces condensation of the DMPA monolayer. The competing effects cause the surface pressure isotherms of mixed DMPA-cholesterol films on a chitosan subphase to be unaffected by the cholesterol mole fraction, due to distinct degrees of chitosan penetration into the film in the presence of cholesterol. By combining polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and sum-frequency generation spectroscopy (SFG), we showed that chitosan induces order into negatively charged phospholipid layers, whereas the opposite occurs for cholesterol. In conclusion, chitosan has its penetration in the film modulated by cholesterol, and electrostatic interactions with negatively charged phospholipids, such as DMPA, are crucial for the action of chitosan.

Enhanced activity of horseradish peroxidase in Langmuir-Blodgett films of phospholipids

The immobilization of enzymes in nanostructured films has potential applications, e.g. in biosensing, for which the activity may not only be preserved, but also enhanced if optimized conditions are identified. Optimization is not straightforward because several requirements must be fulfilled, including a suitable matrix and film-forming technique. In this study, we show that horseradish peroxidase (HRP) has its activity enhanced when immobilized in Langmuir-Blodgett (LB) films, in conjunction with dipalmitoylphosphaticlylglycerol (DPPG). Incorporation of HRP into a DPPG monolayer at the air-water interface was demonstrated with compression isotherms, and Polarization-Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS). From the PM-IRRAS data, we inferred that HRP was not denatured when adsorbed on a pre-formed, low pressure DPPG monolayer. A change in orientation was induced by the phospholipid matrix, with the amide C=O and NH groups from HRP being oriented perpendicular to the surface, parallel to the DPPG acyl chains, i.e. the alpha-helix was inserted into the monolayer. The mixed DPPG-HRP monolayer could be transferred onto solid supports, to which HRP activity was ca. 23% higher than in solution. The control of molecular architecture and choice of a suitable phospholipid matrix allowed HRP-containing LB films to be used in sensing peroxide. (c) 2008 Elsevier B.V. All rights reserved.

Processing of electroactive nanostructured films incorporating carbon nanotubes and phthalocyanines for sensing

The use of carbon nanotubes (CNTs) combined with other materials in nanostructured films has demonstrated their versatility in tailoring specific properties. In this study, we produced layer-by-layer (LbL) films of polyamidoamine-PAMAM-incorporating multiwalled carbon nanotubes (PAMAM-NT) alternated with nickel tetrasulfonated metallophthalocyanine (NiTsPc), in which the incorporation of CNTs enhanced the NiTsPc redox process and its electrocatalytic properties for detecting dopamine. Film growth was monitored by UV-vis spectroscopy, which pointed to an exponential growth of the multilayers, whose roughness increased with the number of bilayers according to atomic force microscopy (AFM) analysis. Strong interactions between -NH3+ terminal groups from PAMAM and -SO3- from NiTsPc were observed via infrared spectroscopy, while the micro-Raman spectra confirmed the adsorption of carbon nanotubes (CNTs) onto the LbL film containing NiTsPc. Cyclic voltammograms presented well-defined electroactivity with a redox pair at 0.86 and 0.87 V, reversibility, a charge-transfer controlled process, and high stability up to 100 cycles. The films were employed successfully in dopamine (DA) detection, with limits of detection and quantification of 10(-7) and 10(-6) mol L-1, respectively. Furthermore, films containing immobilized CNTs could distinguish between DA and its natural interferent, ascorbic acid (AA).

Spectroscopic features of erbium-doped CaM2O6 (M = Nb, Ta) single crystal fibers grown by the laser-heated pedestal growth technique

Erbium-doped single crystal fibers, with low phonon energy and fairly high absorption and emission cross sections are interesting laser active media, for compact, near-infrared and/or upconversion lasers. In this work, high optical quality Er3+-doped CaNb2O6 and CaTa2O6 single crystal fibers were successfully grown by the versatile laser-heated pedestal growth technique, and characterized from the structural and spectroscopic points of view. The results indicate that these crystal fiber compositions, which had not been explored so far, offer potential applications, not only as laser active media, but also in other optical devices. (c) 2007 Elsevier B.V. All rights reserved.

In vitro effect of low-level laser on odontoblast-like cells

The aim of this study was to evaluate the metabolism of odontoblast-like MDPC-23 cells subjected to direct LLL irradiation. The cells were seeded (20,000 cells/well) in 24-well plates and incubated for 24 hours at 37 degrees C. After this period, the culture medium (DMEM) was replaced by fresh DMEM supplemented with 2 or 5% (stress induction by nutritional deficit) or 10% fetal bovine serum (FBS). The cells were exposed to laser doses of 2, 4, 10, 15 and 25 J/cm(2) from a near infrared InGaAsP diode laser prototype (LASERTable; 780 +/- 3 nm, 40 mW). One control group (sham irradiation) was established for each experimental condition (laser dose x FBS supplementation). Three and 72 hours after the last irradiation, cells were analyzed with respect to metabolism, morphology, total protein expression and alkaline phosphatase (ALP) activity. Higher metabolism and total protein expression were observed 72 hours after the last irradiation at the doses of 15 and 25 J/cm(2) (Mann-Whitney; p<0.05). Higher ALP activity was obtained with 5% FBS when the cells were irradiated with doses of 2 and 10 J/cm(2). For the dose of 25 J/cm(2), the highest ALP activity was observed with 10% FBS. It was concluded that the LLLT parameters used in this study stimulated the metabolic activity of the MDPC-23 cells, especially at the doses of 15 and 25 J/cm(2).

Continuous and gradual photo-activation methods: influence on degree of conversion and crosslink density of composite resins

Thermal properties and degree of conversion (DC%) of two composite resins (microhybrid and nanocomposite) and two photo-activation methods (continuous and gradual) displayed by the light-emitting diode (LED) light-curing units (LCUs) were investigated in this study. Differential scanning calorimetry (DSC) thermal analysis technique was used to investigate the glass transition temperature (T(g)) and degradation temperature. The DC% was determined by Fourier transform infrared spectroscopy (FT-IR). The results showed that the microhybrid composite resin presented the highest T(g) and degradation temperature values, i.e., the best thermal stability. Gradual photo-activation methods showed higher or similar T(g) and degradation temperature values when compared to continuous method. The Elipar Freelight 2 (TM) LCU showed the lowest T(g) values. With respect to the DC%, the photo-activation method did not influence the final conversion of composite resins. However, Elipar Freelight 2 (TM) LCU and microhybrid resin showed the lowest DC% values. Thus, the presented results suggest that gradual method photo-activation with LED LCUs provides adequate degree of conversion without promoting changes in the polymer chain of composite resins. However, the thermal properties and final conversion of composite resins can be influenced by the kind of composite resin and LCU.

Increased Viability of Odontoblast-Like Cells Subjected to Low-Level Laser Irradiation

Studies have shown that the increase of cell metabolism depends on the low level laser therapy (LLLT) parameters used to irradiate the cells. However, the optimal laser dose to up-regulate pulp cell activity remains unknown. Consequently, the aim of this study was to evaluate the metabolic response of odontoblast-like cells (MDPC-23) exposed to different LLLT doses. Cells at 20000 cells/cm(2) were seeded in 24-well plates using plain culture medium (DMEM) and were incubated in a humidified incubator with 5% CO(2) at 37 degrees C. After 24 h, the culture medium was replaced by fresh DMEM supplemented with 5% (stress by nutritional deficit) or 10% fetal bovine serum (FBS). The cells were exposed to different laser doses from a near infrared diode laser prototype designed to provide a uniform irradiation of the wells. The experimental groups were: G1: 1.5 J/cm(2) + 5% FBS; G2: 1.5 J/cm(2) + 10% FBS; G3: 5 J/cm(2) + 5% FBS; G4: 5 J/cm(2) + 10% FBS; G5: 19 J/cm(2) + 5% FBS; G6: 19 J/cm(2) + 10% FBS. LLLT was performed in 3 consecutive irradiation cycles with a 24-hour interval. Non-irradiated cells cultured in DMEM supplemented with either 5 or 10% FBS served as control groups. The analysis of the metabolic response was performed by the MTT assay 3 h after the last irradiation. G1 presented an increase in SDH enzyme activity and differed significantly (Mann-Whitney test, p < 0.05) from the other groups. Analysis by scanning electron microscopy showed normal cell morphology in all groups. Under the tested conditions, LLLT stimulated the metabolic activity of MDPC-23 cultured in DMEM supplemented with 5% FBS and exposed to a laser dose of 1.5 J/cm(2). These findings are relevant for further studies on the action of near infrared lasers on cells with odontoblast phenotype.

Synthesis, characterization, crystal structure, and biological studies of vanadium complexes with glycolic acid

Synthesis, characterization, crystal structure, and biological studies of two complexes with glycolic acid are described. The solid complexes were formulated as K2[VO(C2H2O3)(C2H3O3)2] H2O (1) and K2[{VO2(C2H2O3)}2] (2) and characterized by X-ray studies, Fourier transform infrared spectroscopy (FTIR), Electron paramagnetic resonance (EPR), and magnetic susceptibility. Conversion of 1 to 2 was studied in aqueous solution by UV-Vis spectroscopy and in the solid state by diffuse reflectance spectroscopy. Complex 2 contains dinuclear [{VO2(C2H2O3)}2]2- anions in which glycolate(2-) is a five-membered chelating ring formed by carboxylate and -hydroxy groups. The geometry around the vanadium in 2 was interpreted as intermediate between a trigonal bipyramid and a square pyramid. Vanadium(IV) is pentacoordinate in 1 as a distorted square pyramid. Complex 1 contains a vanadyl group (V=O) surrounded by two oxygens from deprotonated carboxylate and hydroxy groups forming a five-membered ring. Two oxygens from different glycolates(1-) are bonded to the (V=O) also. Biological analysis for potential cytotoxic effects of 1 was performed using Human Cervix Adenocarcinoma (HeLa) cells, a human cervix adenocarcinoma-derived cell line. After incubation for 48 h, 1 causes 90 and 95% of HeLa cells death at 20 and 200 mol L-1, respectively.

Effect of Lithium Nitrate on the Alkali-Silica Reaction Gel

Lithium nitrate has been used to prevent and to mediate the expansion caused by alkali-silica reaction (ASR). However, there is limited information on how it affects the existing reaction products caused by ASR. The aim of the present work is to determine the modifications caused by the LiNO3 treatment on the structure of the gel produced by ASR. ASR gel samples obtained from a concrete dam were exposed to an aqueous solution of lithium nitrate and sodium hydroxide with molar LiNO3/NaOH = 0.74, and the resulting products were analyzed by X-ray diffraction, infrared spectroscopy, and solid-state nuclear magnetic resonance of Si-29, Na-23, and Li-7. The treatment of the gel samples produces significant structural modifications in ASR products. A new amorphous silicate compound incorporating Li+ ions is formed, with an average silicate network that can be described as linear in contrast with the layered structure of the original gel. This elimination of the layered structure after the Li-based treatments may be related to the reduction of the tendency of the gel to expand. Also, several crystalline compounds containing potassium indicate the release of this species from the original ASR gel.

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.

Synthesis, characterization and cytotoxic activities of the [RuCl(2)(NO)(dppp)(L)]PF(6) complexes

The synthesis and characterization of ruthenium compounds of the type [RuCl(2)(NO)(dppp)(L)]PF(6) [dppp = 1,3-bis(diphenylphosphino)propane; L = pyridine, 4-methylpyridine, 4-phenylpyridine and dimethyl sulfoxide] are described. The complexes were characterized by elemental analysis, UV/Vis and infrared spectroscopy, cyclic voltammetry, and X-ray crystallography for the complexes with the pyridine and 4-methylpyridine ligands. In vitro evaluation of these nitrosyl complexes revealed cytotoxic activity from 7.1 to 19.0 mu M against the MDA-MB-231 breast tumor cells and showed that, in this case, they are more active than the reference metallodrug cisplatin. The 1,3-bis(diphenylphosphino)propane and the N-heterocyclic ligands alone failed to show cytotoxic activities at the concentrations tested (maximum concentration utilized = 200 mu M). (C) 2009 Elsevier Inc. All rights reserved.