Dental dimethacrylate-based nanohybrid composite Kalore GC: Kinetic study of its light-curing

AbstractObjectiveThis study investigated the light-curing kinetic of the novel dental dimethacrylate-based nanohybrid composite (Kalore GC). Its organic matrix consists of a high molecular weight monomer called DX 511 as well as the known dimethacrylate monomers bisphenol A ethyl dimethacrylate (Bis-EMA) and urethane dimethacrylate (UDMA).MethodsFour properties were measured: degree of conversion (DC), depth of curing (DOC), polymerization shrinkage (S) and glass transition temperature (Tg) versus curing time. These properties were measured by spectroscopic imaging in Attenuated Total Reflection (ATR-FT-IR), scrape test, density measurements and dynamic mechanical thermal analysis (DMTA), respectively.ResultsAfter 10s of light curing, the DC was 2.50%, DOC 1.86 mm and S 1.48%. The composite cured for 10s showed two Tg; 56.4 °C and 112.8 °C. At this stage, the maximum rate of polymerization was noticed. The curing, however, continued with much lower and decreased rate for up to 100s. There, a maximum DC of about 40% and a maximum DOC of about 3.5 mm were observed. Tg values were raised to 59.5 and 102.3 °C, respectively.ConclusionsWithin the condition of this study, the optimum curing time of Kalore GC seems to be 100 s. The composite light-cured up to 300 s showed two Tg, indicating that this compound still contained unreacted double bonds of C=C and macroradicals, which continued to cure upon heating in DMTA

Association Between Breastfeeding and the Development of Childhood Diabetes Mellitus Type I (DM I): The Effect of Prolonged Exclusive Breastfeeding on Gut Microbiome and the Link with DM I

The role of breastfeeding and dietary habits was studied in 10 children with DM I (case group) and compared with 10 healthy controls. Our results showed that the case group had significantly shorter exclusive breastfeeding duration compared with the control group (p = 0.006). An in silico comparative analysis of gut microbiota data from two recent studies was also performed in order to identify any specific bacterial genera potentially associated with DM I, due to prolonged breastfeeding. The Pasteurellaceae family, found in breast milk, was shown to have a significantly higher population in the intestine in the control group (p = 0.010). Overall, this preliminary study showed that exclusive breastfeeding duration is strongly associated with DM I. An association between breast milk microbiome and gut microbiome was also observed. This should encourage further research, aiming to examine both the effect of breastfeeding on gut microbiome and the possible links with DM I

Progression of mouse skin carcinogenesis is associated with increased ERα levels and is repressed by a dominant negative form of ERα.

Estrogen receptors (ER), namely ERα and ERβ, are hormone-activated transcription factors with an important role in carcinogenesis. In the present study, we aimed at elucidating the implication of ERα in skin cancer, using chemically-induced mouse skin tumours, as well as cell lines representing distinct stages of mouse skin oncogenesis. First, using immunohistochemical staining we showed that ERα is markedly increased in aggressive mouse skin tumours in vivo as compared to the papilloma tumours, whereas ERβ levels are low and become even lower in the aggressive spindle tumours of carcinogen-treated mice. Then, using the multistage mouse skin carcinogenesis model, we showed that ERα gradually increases during promotion and progression stages of mouse skin carcinogenesis, peaking at the most aggressive stage, whereas ERβ levels only slightly change throughout skin carcinogenesis. Stable transfection of the aggressive, spindle CarB cells with a dominant negative form of ERα (dnERα) resulted in reduced ERα levels and reduced binding to estrogen responsive elements (ERE)-containing sequences. We characterized two highly conserved EREs on the mouse ERα promoter through which dnERα decreased endogenous ERα levels. The dnERα-transfected CarB cells presented altered protein levels of cytoskeletal and cell adhesion molecules, slower growth rate and impaired anchorage-independent growth in vitro, whereas they gave smaller tumours with extended latency period of tumour onset in vivo. Our findings suggest an implication of ERα in the aggressiveness of spindle mouse skin cancer cells, possibly through regulation of genes affecting cell shape and adhesion, and they also provide hints for the effective targeting of spindle cancer cells by dnERα

Mutational analysis of the major proline transporter (PrnB) of Aspergillus nidulans

PrnB, the L-proline transporter of Aspergillus nidulans, belongs to the Amino acid Polyamine Organocation (APC) transporter family conserved in prokaryotes and eukaryotes. In silico analysis and limited biochemical evidence suggest that APC transporters comprise 12 transmembrane segments (TMS) connected with relatively short hydrophilic loops (L). However, very little is known on the structure-function relationships in APC transporters. This work makes use of the A. nidulans PrnB transporter to address structure-function relationships by selecting, constructing and analysing several prnB mutations. In the sample, most isolated missense mutations affecting PrnB function map in the borders of cytoplasmic loops with transmembrane domains. These are I119N and G120W in L2-TMS3, F278V in L6-TMS7, NRT378NRTNRT and PY382PYPY in L8-TMS9 and T456N in L10-TMS11. A single mutation (G403E) causing, however, a very weak phenotype, maps in the borders of an extracellular loop (L9-TMS10). An important role of helix TMS6 for proline binding and transport is supported by mutations K245L and, especially, F248L that clearly affect PrnB uptake kinetics. The critical role of these residues in proline binding and transport is further shown by constructing and analysing isogenic strains expressing selected prnB alleles fused to the gene encoding the Green Fluorescent Protein (GFP). It is shown that, while some prnB mutations affect proper translocation of PrnB in the membrane, at least two mutants, K245E and F248L, exhibit physiological cellular expression of PrnB and, thus, the corresponding mutations can be classified as mutations directly affecting proline binding and/or transport. Finally, comparison of these results with analogous studies strengthens conclusions concerning amino acid residues critical for function in APC transporters

Water absorption and degradation characteristics of chitosan-based polyesters and hydroxyapatite composites

Blends of chitosan and biodegradable synthetic aliphatic polyesters (polycaprolactone, poly-(butylene succinate), poly[(butylene succinate)-co-adipate], poly[(butylene terephthalate)-co-adipate], and poly(lactic acid)) were injection-molded. These samples were immersed in isotonic solution at 37ºC for a period of 60 d. The water uptake and the degradation properties, as measured by the loss in tensile strength, were evaluated as a function of time. In this study, the rate and the equilibriumwater uptake were proportional to the amount of chitosan in the blend. The addition of HA to chitosan and polyester significantly reduced the equilibrium water uptake. The water uptake did not follow the classical Fickian phenomena and could be expressed by a two-stage sorption non-Fickian diffusion model. Contact angle measurement was used to quantify the changes in surface hydrophilicity as a function of chitosan and polyester composition. The glycerol contact angle decreased with increasing synthetic components in the blend. The blends and composites also showed increased degradation, as quantified by a loss in their mechanical properties, with increase in natural content. The degradation of properties was directly related to the water uptake of the blends; the higher the water uptake, the higher the degradation. Pure polyesters, while having low water uptake, nevertheless showed significant degradation by a precipitous drop in the strain at break. Among the polyesters, poly(lactic acid) displayed maximum degradation, while polycaprolactone displayed the least.Blends of chitosan and biodegradable synthetic aliphatic polyesters (polycaprolactone, poly(butylene succinate), poly[(butylene succinate)-co-adipate], poly[(butylene terephthalate)co-adipate], and poly(lactic acid)) were injection-molded. These samples were immersed in isotonic solution at 37 degrees C for a period of 60 d. The water uptake and the degradation properties, as measured by the loss in tensile strength, were evaluated as a function of time. In this study, the rate and the equilibrium water uptake were proportional to the amount of chitosan in the blend. The addition of HA to chitosan and polyester significantly reduced the equilibrium water uptake. The water uptake did not follow the classical Fickian phenomena and could be expressed by a two-stage sorption non-Fickian diffusion model. Contact angle measurement was used to quantify the changes in surface hydrophilicity as a function of chitosan and polyester composition. The glycerol contact angle decreased with increasing synthetic components in the blend. The blends and composites also showed increased degradation, as quantified by a loss in their mechanical properties, with increase in natural content. The degradation of properties was directly related to the water uptake of the blends; the higher the water uptake, the higher the degradation. Pure polyesters, while having low water uptake, nevertheless showed significant degradation by a precipitous drop in the strain at break. Among the polyesters, poly(lactic acid) displayed maximum degradation, while polycaprolactone displayed the least

Enzyme-catalyzed hydrolysis of dentin adhesive containing a new urethane-based trimethacrylate monomer

A new trimethacrylate monomer with urethane-linked groups, 1,1,1-tri-[4-(methacryloxyethylamino-carbonyloxy)-phenyl]ethane (MPE), was synthesized, characterized, and used as a co-monomer in dentin adhesives. Dentin adhesives containing 2-hydroxyethyl methacrylate (HEMA, 45% w/w) and 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane (BisGMA, 30% w/w) in addition to MPE (25% w/w) were formulated with H2O at 0 (MPE0), 8 (MPE8) and 16 wt % water (MPE16) to simulate the wet demineralized dentin matrix and compared with controls [HEMA/BisGMA, 45/55 w/w, at 0 (C0), 8 (C8) and 16 wt% water (C16)]. The new adhesive showed a degree of double bond conversion and mechanical properties comparable with control, with good penetration into the dentin surface and a uniform adhesive/dentin interface. On exposure to porcine liver esterase, the net cumulative methacrylic acid (MAA) release from the new adhesives was dramatically (P < 0.05) decreased relative to the control, suggesting that the new monomer improves esterase resistance

Chemorheology of photopolymerizable acrylates using a modified Boltzmann sigmoidal model

Experiments were conducted to evaluate the influence of ambient photoconversion on rheology for a range of photopolymerizable urethane dimethacrylate (UDMA) resins containing varying amounts of three comonomers including 1,6 hexane diol-dimethacrylate (HDDMA), an alkoxylated cyclohexane dimethanol diacrylate monomer (CD-582), and hydroxyethyl methacrylate (HEMA). Experiments were performed both as a function of composition and time-dependent dose varying the intensity using a photorheometer. A semilog-based sigmoidal model allowed the determination of four physical model parameters to define the relationship between reaction kinetics and its dynamic influence on viscosity. We have observed induction times and viscosity changes associated with the model that shows a trend in reaction kinetics in the following order from most to least reactive: UDMA > CD582 > HDDMA > HEMA. With increasing amounts of reactive diluent included in the formulation, the kinetics of reaction was more sluggish. The value of this sigmoidal model is that it could help define formulation and process conditions most likely to control crosslinking to maximize dimensional stability or other thermophysical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2319–2325, 2008Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61230/1/21563_ftp.pd