Degree of Conversion and BisGMA, TEGDMA, UDMA Elution from Flowable Bulk Fill Composites.

The degree of conversion (DC) and the released bisphenol A diglycidyl ether dimethacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) monomers of bulk-fill composites compared to that of conventional flowable ones were assessed using micro-Raman spectroscopy and high performance liquid chromatography (HPLC). Four millimeter-thick samples were prepared from SureFil SDR Flow (SDR), X-tra Base (XB), Filtek Bulk Fill (FBF) and two and four millimeter samples from Filtek Ultimate Flow (FUF). They were measured with micro-Raman spectroscopy to determine the DC% of the top and the bottom surfaces. The amount of released monomers in 75% ethanol extraction media was measured with HPLC. The differences between the top and bottom DC% were significant for each material. The mean DC values were in the following order for the bottom surfaces: SDR_4mm_20s > FUF_2mm_20s > XB_4mm_20s > FBF_4mm_20s > XB_4mm_10s > FBF_4mm_10s > FUF_4mm_20s. The highest rate in the amount of released BisGMA and TEGDMA was found from the 4 mm-thick conventional flowable FUF. Among bulk-fills, FBF showed a twenty times higher amount of eluted UDMA and twice more BisGMA; meanwhile, SDR released a significantly higher amount of TEGDMA. SDR bulk-fill showed significantly higher DC%; meanwhile XB, FBF did not reach the same level DC, as that of the 2 mm-thick conventional composite at the bottom surface. Conventional flowable composites showed a higher rate of monomer elution compared to the bulk-fills, except FBF, which showed a high amount of UDMA release.

Fluorescence spectroscopic investigation of competitive interactions between ochratoxin A and 13 drug molecules for binding to human serum albumin.

Ochratoxin A (OTA) is a highly toxic mycotoxin found worldwide in cereals, foods, animal feeds and different drinks. Based on previous studies, OTA is one of the major causes of the chronic tubulointerstitial nephropathy known as Balkan endemic nephropathy (BEN) and exerts several other adverse effects shown by cell and/or animal models. It is a well-known fact that OTA binds to various albumins with very high affinity. Recently, a few studies suggested that reducing the bound fraction of OTA might reduce its toxicity. Hypothetically, certain drugs can be effective competitors displacing OTA from its albumin complex. Therefore, we examined 13 different drug molecules to determine their competing abilities to displace OTA from human serum albumin (HSA). Competitors and ineffective chemicals were identified with a steady-state fluorescence polarization-based method. After characterization the competitive abilities of individual drugs, drug pairs were formed and their displacing activity were tested in OTA-HSA system. Indometacin, phenylbutazone, warfarin and furosemide showed the highest competing capacity but ibuprofen, glipizide and simvastatin represented detectable interaction too. Investigations of drug pairs raised the possibility of the presence of diverse binding sites of competing drugs. Apart from the chemical information obtained in our model, this explorative research might initiate future designs for epidemiologic studies to gain further in vivo evidence of long-term (potentially protective) effects of competing drugs administered to human patients.

The Effect of Heat Treatment of ß-Tricalcium Phosphate-Containing Silica-Based Bioactive Aerogels on the Cellular Metabolism and Proliferation of MG63 Cells.

ß-Tricalcium phosphate was combined with silica aerogel in composites prepared using the sol-gel technique and supercritical drying. The materials were used in this study to check their biological activity and bone regeneration potential with MG63 cell experiments. The composites were sintered in 100 °C steps in the range of 500-1000 °C. Their mechanical properties, porosities, and solubility were determined as a function of sintering temperature. Dissolution studies revealed that the released Ca-/P molar ratios appeared to be in the optimal range to support bone tissue induction. Cell viability, ALP activity, and type I collagen gene expression results all suggested that the sintering of the compound at approximately 700-800 °C as a scaffold could be more powerful in vivo to facilitate bone formation within a bone defect, compared to that documented previously by our research team. We did not observe any detrimental effect on cell viability. Both the alkaline phosphatase enzyme activity and the type I collagen gene expression were significantly higher compared with the control and the other aerogels heat-treated at different temperatures. The mesoporous silica-based aerogel composites containing ß-tricalcium phosphate particles treated at temperatures lower than 1000 °C produced a positive effect on the osteoblastic activity of MG63 cells. An in vivo 6 month-long follow-up study of the mechanically strongest 1000 °C sample in rat calvaria experiments provided proof of a complete remodeling of the bone.

The Effect of the PVA/Chitosan/Citric Acid Ratio on the Hydrophilicity of Electrospun Nanofiber Meshes.

In this study, scaffolds were prepared via an electrospinning method for application in oral cavities. The hydrophilicity of the fiber mesh is of paramount importance, as it promotes cell spreading; however, the most commonly used polyvinyl alcohol (PVA) and other hydrophilic fiber meshes immediately disintegrate in aqueous media. In contrast, the excessive hydrophobicity of the scaffolds already inhibits cells adhesion on the surface. Therefore, the hydrophilicity of the fiber meshes needed to be optimized. Scaffolds with different polyvinyl alcohol (PVA)/chitosan/citric acid ratios were prepared. The addition of chitosan and the heat initiated cross-linkage of the polymers via citric acid enhanced the scaffolds' hydrophobicity. The optimization of this property could be followed by contact angle measurements, and the increased number of cross-linkages were also supported by IR spectroscopy results. The fibers' physical parameters were monitored via low-vacuum scanning electron microscopy (SEM) and atomic force microscopy (AFM). As biocompatibility is essential for dental applications, Alamar Blue assay was used to prove that meshes do not have any negative effects on dental pulp stem cells. Our results showed that the optimization of the fiber nets was successful, as they will not disintegrate in intraoral cavities during dental applications.

Interaction of ochratoxin A with quaternary ammonium beta-cyclodextrin.

Ochratoxin A (OTA) is a widely spread nephrotoxic food contaminant mycotoxin. Unfortunately, attenuation or prevention of the toxic effects of OTA is still an unresolved problem. Molecular inclusion of OTA by cyclodextrins (CDs) results in complexes with low stability. In the human organism, OTA exists mostly in the dianionic state (OTA(2-)). Therefore, our major goal was to develop a chemically modified cyclodextrin which gives a more stable complex with OTA than the previously published derivatives and which shows stronger preference towards OTA(2-). In our fluorescence spectroscopic study we demonstrate that quaternary ammonium beta-cyclodextrin (QABCD) fulfils both of these requirements. The calculated stability constant of the QABCD-OTA(2-) complex was 28,840 M(-1) (about 200-fold higher than that of the ß-CD-OTA(2-) complex). We hypothesize, that QABCD may be a suitable tool for the decontamination of different OTA-contaminated drinks; furthermore, for alleviation of the toxic effects of OTA, such complex formation may reduce its absorption from the intestine.

Regulation of cytotoxic, non-estrogenic, oxidative stress-induced processes of zearalenone in the fission yeast Schizosaccharomyces pombe.

This study investigates the non-estrogenic mode of zearalenone (ZEA) toxicity in a novel aspect via accumulation of reactive oxygen species (ROS) and the regulation of the activities of antioxidant enzymes in the Schizosaccharomyces pombe in acute toxicity tests. In comparison with the control, 500 µM ZEA treatment caused 66% decrease in the concentration of glutathione (GSH), which was a consequence, in the absence of ZEA-GSH interaction, of the GSH-consuming processes of the antioxidant system; this depletion of GSH initiated a 1.8- and 2.0-fold accumulation of the superoxide anion and hydrogen peroxide, but did not increase the concentration of the hydroxyl radical; ROS-induced adaptation processes via activation of the Pap1 transcription factor resulted in significantly increased activities of superoxide dismutases, catalase, glutathione reductase and glutathione S-transferase, and decreased activities of glutathione peroxidase and glucose-6-phosphate dehydrogenase. This treatment altered the sterol composition of the cells by inducing decreased concentrations of ergosterol, squalene and 24-methylene-24,25-hydrolanosterol, and also elevated the number of fragmented nuclei. Cells strived to correct the unbalanced redox state by regulation of the antioxidant system, but this was not enough to defend the cells from the disturbed sterol composition, the cell cycle arrest, and the fragmentation of nuclei.

Citrinin-induced fluidization of the plasma membrane of the fission yeast Schizosaccharomyces pombe.

Citrinin (CTN) is a toxic fungal metabolite that is a hazardous contaminant of foods and feeds. In the present study, its acute toxicity and effects on the plasma membrane of Schizosaccharomyces pombe were investigated. The minimum inhibitory concentration of CTN against the yeast cells proved to be 500 µM. Treatment with 0, 250, 500 or 1000 µM CTN for 60 min resulted in a 0%, 2%, 21% or 100% decrease, respectively, in the survival rate of the cell population. Treatment of cells with 0, 100, 500 or 1000 µM CTN for 20 min induced decrease in the phase-transition temperature of the 5-doxylstearic acid-labeled plasma membrane to 16.51, 16.04, 14.18 or 13.98°C, respectively as measured by electron paramagnetic resonance spectroscopy. This perturbation was accompanied by the efflux of essential K⁺ from the cells. The existence of an interaction between CTN and glutathione was detected for the first time by spectrofluorometry. Our observations may suggest a direct interaction of CTN with the free sulfhydryl groups of the integral proteins of the plasma membrane, leading to dose-dependent membrane fluidization. The change in fluidity disturbed the ionic homeostasis, contributing to the death of the cells, which is a novel aspect of CTN cytotoxicity.

The effect of temperature on the color of red wines.

UNLABELLED: The effect of increased temperature on the color of red wines was studied due to its importance during storage and transport. The chemical reactions induced by elevated temperature were investigated by measuring the UV-VIS spectra. The temperature of the wines was increased from its common storage temperature (about 14 °C) to higher temperatures (t= 20 °C, 25 °C, 30 °C, 35 °C, and 40 °C) and the UV/VIS spectra were recorded during several hours. The spectral changes obtained indicate the presence of quasi-first-order chemical processes justifying determination of the activation energies using their temperature dependence. The determined decay values (Villányi Portugieser: E(VP) (a,420 nm) = 90.02 kJ/mol, E(VP) (a,520 nm) = 34.18 kJ/mol, E(VP) (a,620 nm) = 54.55 kJ/mol; half-life values of 46.5 d [25 °C] and 9.5 d [35 °C] at 420 nm; 4.67 d [25 °C] and 2.0 d [35 °C] at 520 nm; 9.5 d [25 °C] and 2.4 d [35 °C] at 620 nm; Bikatory wine: E(Bk) (a,420 nm) = 82.07 kJ/mol and half-life values of 41.35 d [25 °C] and 4.001 d [35 °C] at 420 nm) of these reactions highlight a considerable change in the quality of wines stored for a few hours at elevated temperatures. Depending on polyphenol composition the wines show different half-life with regard to their color stability and browning reactions. Higher polyphenolic content helps to stabilize the wine against detrimental temperature effects. PRACTICAL APPLICATION: This research can be applicable to estimate the optimal temperature of red wines during storage and transport.