Effects of different particle deposition parameters on adhesion of resin cement to zirconium dioxide and phase transformation

This study evaluated the effect of air-abrasion parameters such as particle size, distance, and time on adhesion of resin cement to zirconium dioxide (Y-TZP) and t→m phase transformation. Y-TZP blocks (N = 80) (In-Ceram YZ, Vita) (4 mm^3?×?4 mm^3?×?3 mm³) were assigned into eight groups (n = 10): air-abrasion with 30 μm (CoJet Sand, S30) and 110 μm (Rocatec-Plus, S110) silica-coated alumina particles, applied for either for 10–20 s (T = time), from a distance of 10–20 mm (D = distance), composing the following groups: S₃₀T₁₀D₁₀, S₃₀T₁₀D₂₀, S₃₀T₂₀D₁₀, S₃₀T₂₀D₂₀, S₁₁₀T₁₀D₁₀, S₁₁₀T₁₀D₂₀, S₁₁₀T₂₀D₁₀, and S₁₁₀T₂₀D₂₀. Resin composite (RelyX ARC) was bonded to Y-TZP blocks in polyethylene molds. The specimens were aged (10,000 thermal cycles and water storage for 90 days) prior to shear bond test. Failure types were analyzed under stereomicroscope and SEM, and phase transformation was calculated. Data (MPa) were analyzed using 3-way ANOVA and Tukey’s tests. Air-abrasion with 110 μm silica particles (10.96) presented significantly higher bond strength (p = 0.0149) compared to 30 μm (8.96). Time (p = 0.403) and distance (p = 0.179) parameters did not affect the results significantly. Air-abrasion with 110 μm particles (12.3) promoted higher bond strength than that of 30 μm (6.4) when applied for 10 s from a distance of 10 mm (Tukey’s). Failure types were predominantly adhesive. Phase transformation ranged between 30.3 and 35.9% for 30 μm particles and 23.8–43.7% for 110 μm particles. While the size of silica-coated alumina particles were more relevant parameter for resin cement adhesion to Y-TZP, time (up to 20 s) and distance (up to 20 mm) appear to be less pertinent.     

Higher dietary magnesium intake is associated with lower body mass index,waist circumference and serum glucose in Mexican adults

Background

Obesity and diabetes mellitus (DM) are public health concerns in Mexico of top-level priority due to their high prevalence and their growth rate in recent decades. The accumulation of adipose tissue leads to an unbalanced release of pro-oxidant factors, which causes cellular damage and favors the development of comorbidities. Recent evidence suggests that oxidative stress also promotes the accumulation of adipose tissue and the development of insulin resistance. The objective of this study is to evaluate the association between usual intake of antioxidant nutrients, specifically vitamins A, C, E and magnesium with body mass index (BMI), waist circumference (WC) and serum glucose concentrations in a representative sample of Mexican adults.

Methodology

We analyzed data on diet, BMI, WC and serum glucose from the Mexican National Health and Nutrition Survey 2012. Analysis included 20- to 65-year-old adults without a known diagnosis of DM (n?=?1573). Dietary information was obtained using the five-step multiple-pass method developed by the United States Department of Agriculture and adapted to the Mexican context. Nutrient usual intake distributions were estimated using the Iowa State University method, through the “Software for Intake Distribution Estimation” (PC-Side) v.1.02. Associations were analyzed using multivariate regression models.

Results

Higher dietary magnesium intake was associated with lower markers of adiposity, so that an increase in 10?mg per 1000?kcal/day of magnesium was associated with an average decrease in BMI of 0.72% (95% CI: -1.36, ??0.08) and 0.49?cm (95% CI: -0.92, ??0.07) of WC. Additionally, in women with normal glucose concentrations, an increase in magnesium intake was associated with an average decrease in serum glucose by 0.59% (95% CI: -1.08, ??0.09).

Conclusion

The results suggest that magnesium intake is associated with lower BMI, WC and serum glucose in Mexican population. However, more studies are required to elucidate the nature of this association.

     

Dehydropeptide Supramolecular Hydrogels and Nanostructures as Potential Peptidomimetic Biomedical Materials

Supramolecular peptide hydrogels are gaining increased attention, owing to their potential in a variety of biomedical applications. Their physical properties are similar to those of the extracellular matrix (ECM), which is key to their applications in the cell culture of specialized cells, tissue engineering, skin regeneration, and wound healing. The structure of these hydrogels usually consists of a di- or tripeptide capped on the N-terminus with a hydrophobic aromatic group, such as Fmoc or naphthalene. Although these peptide conjugates can offer advantages over other types of gelators such as cross-linked polymers, they usually possess the limitation of being particularly sensitive to proteolysis by endogenous proteases. One of the strategies reported that can overcome this barrier is to use a peptidomimetic strategy, in which natural amino acids are switched for non-proteinogenic analogues, such as D-amino acids, β-amino acids, or dehydroamino acids. Such peptides usually possess much greater resistance to enzymatic hydrolysis. Peptides containing dehydroamino acids, i.e., dehydropeptides, are particularly interesting, as the presence of the double bond also introduces a conformational restraint to the peptide backbone, resulting in (often predictable) changes to the secondary structure of the peptide. This review focuses on peptide hydrogels and related nanostructures, where α,β-didehydro-α-amino acids have been successfully incorporated into the structure of peptide hydrogelators, and the resulting properties are discussed in terms of their potential biomedical applications. Where appropriate, their properties are compared with those of the corresponding peptide hydrogelator composed of canonical amino acids. In a wider context, we consider the presence of dehydroamino acids in natural compounds and medicinally important compounds as well as their limitations, and we consider some of the synthetic strategies for obtaining dehydropeptides. Finally, we consider the future direction for this research area.     

Complement-Opsonized Nano-Carriers Are Bound by Dendritic Cells (DC) via Complement Receptor (CR)3, and by B Cell Subpopulations via CR-1/2, and Affect the Activation of DC and B-1 Cells

The development of nanocarriers (NC) for biomedical applications has gained large interest due to their potential to co-deliver drugs in a cell-type-targeting manner. However, depending on their surface characteristics, NC accumulate serum factors, termed protein corona, which may affect their cellular binding. We have previously shown that NC coated with carbohydrates to enable biocompatibility triggered the lectin-dependent complement pathway, resulting in enhanced binding to B cells via complement receptor (CR)1/2. Here we show that such NC also engaged all types of splenic leukocytes known to express CR3 at a high rate when NC were pre-incubated with native mouse serum resulting in complement opsonization. By focusing on dendritic cells (DC) as an important antigen-presenting cell type, we show that CR3 was essential for binding/uptake of complement-opsonized NC, whereas CR4, which in mouse is specifically expressed by DC, played no role. Further, a minor B cell subpopulation (B-1), which is important for first-line pathogen responses, and co-expressed CR1/2 and CR3, in general, engaged NC to a much higher extent than normal B cells. Here, we identified CR-1/2 as necessary for binding of complement-opsonized NC, whereas CR3 was dispensable. Interestingly, the binding of complement-opsonized NC to both DC and B-1 cells affected the expression of activation markers. Our findings may have important implications for the design of nano-vaccines against infectious diseases, which codeliver pathogen-specific protein antigen and adjuvant, aimed to induce a broad adaptive cellular and humoral immune response by inducing cytotoxic T lymphocytes that kill infected cells and pathogen-neutralizing antibodies, respectively. Decoration of nano-vaccines either with carbohydrates to trigger complement activation in vivo or with active complement may result in concomitant targeting of DC and B cells and thereby may strongly enhance the extent of dual cellular/humoral immune responses.     

Programmed Cell Death in the Small Intestine: Implications for the Pathogenesis of Celiac Disease

The small intestine has a high rate of cell turnover under homeostatic conditions, and this increases further in response to infection or damage. Epithelial cells mostly die by apoptosis, but recent studies indicate that this may also involve pro-inflammatory pathways of programmed cell death, such as pyroptosis and necroptosis. Celiac disease (CD), the most prevalent immune-based enteropathy, is caused by loss of oral tolerance to peptides derived from wheat, rye, and barley in genetically predisposed individuals. Although cytotoxic cells and gluten-specific CD4⁺ Th1 cells are the central players in the pathology, inflammatory pathways induced by cell death may participate in driving and sustaining the disease through the release of alarmins. In this review, we summarize the recent literature addressing the role of programmed cell death pathways in the small intestine, describing how these mechanisms may contribute to CD and discussing their potential implications.     

Theoretical Study of the Water–Gas Shift Reaction on a Au/Hematite Model Catalyst

Topics in Catalysis - Using the density functional theory, the mechanism of the water–gas shift reaction has been investigated employing a model catalyst formed by a Au5 cluster supported on...     

Assessment of the Physicochemical Properties and Oxidative Stability of Kernel Fruit Oil from the Acrocomia totai Palm Tree

This study investigated the effects of variations in oil contents and fatty-acid composition, density, viscosity, acid values, saponification values, specific oxidative stability, and antioxidant concentration of Acrocomia totai kernel oil during fruit maturation. Fatty acids were quantified using ¹H nuclear magnetic resonance (NMR) spectroscopy, gas chromatograph-flame-ionization detector (GC-FID), and Fourier transform Raman (FT-Raman) spectroscopy analyses. The results showed that all physicochemical characteristics and oil composition changed during the ripening stage. The CG-FID analysis showed a reduction in the unsaturated fatty-acid content (from 78.8% to 22.1%), with a proportional increase in the saturated fatty-acid contents (from 21.6% to 77.9%). The difference in the fatty-acid composition was confirmed by analysis of the ¹H NMR and FT-Raman spectra. The degree of unsaturation was calculated to determine the oxidative stability of oil. These results suggest that the fruit's maturation contributes to the specific oxidative stability. The antioxidant concentration revealed higher contents of carotenoids in the ripe fruit (0.16 mg of carotenoid per 100 g_KERNEL) when compared to the unripe fruit (0.05 mg of carotenoid per 100 g_KERNEL). In the total phenolics analysis, there was no change in concentration over ripening time. These results show that kernel oil has physicochemical properties comparable with high-quality commercial vegetable oils, suggesting that it is a promising alternative to conventional vegetable oils.     

The Application of Biomaterials in the Treatment of Platinum-Resistant Ovarian Cancer

More than 70 % of women with ovarian cancer are diagnosed with advanced-stage disease, which is initially treated with cytoreductive surgery, and combination chemotherapy with platinum-based compounds. Most patients initially respond to platinum-based therapy, but eventually up to 80 % of this responsive cohort becomes refractory due to the development of platinum resistance. This review discusses current and potential therapeutic approaches that exploit biomaterial-based applications to combat platinum resistance either by enhancing the delivery of platinum-based drugs or prodrugs, delivering other toxic non-platinum-based bioactive factors (by themselves or in combination with platinum-based drugs) or by delivering other bioactive factors that re-sensitize resistant ovarian cancer cells to these drugs. The types of materials that are used, the bioactive factors applied (i.e., drug or gene delivery), and the specific agents that are employed to target these types of cancer cells are discussed. We conclude that the unique attributes of biomaterial-based applications can be further explored toward overcoming platinum-resistant ovarian cancer as monotherapy, or in combination with other treatment strategies.     

Nanocomposites of PBAT and cellulose nanocrystals modified by in situ polymerization and melt extrusion

Cellulose nanocrystals (CNC) were successfully grafted with a low molecular weight poly(butylene glutarate) through an in situ polymerization procedure. The grafting treatment decreased the CNC hydrophilic character and increased the onset of their thermal degradation by approximately 20°C, thus increasing the possibilities of CNC application. Composites of grafted and nongrafted CNC with a poly(butylene‐adipate‐co‐terephthalate) (PBAT) matrix were prepared by melt extrusion. The CNC addition led to an increase of 50% of the tensile elastic modulus of the PBAT. In addition, dynamic mechanical thermal analysis showed that the composite with CNC retained its high modulus even at temperatures far above the glass transition temperature of PBAT. At 60°C the storage modulus of the composite with CNC was approximately 200% higher than that of the pure PBAT. Thus, in this work, nanocomposites of improved properties were obtained through a combination of in situ polymerization and melt extrusion. POLYM. ENG. SCI., 56:1339–1348, 2016. © 2016 Society of Plastics Engineers     

Sorption of propylene and propane in polyurethane membranes containing silver nanoparticles

The preparation of a facilitated transport membrane of polyurethane (PU) containing silver nanoparticles is reported. The propylene and propane sorption was investigated aiming at the selective separation from C3s mixtures. The silver particles were photogenerated in situ into the polyurethane matrix using UV light radiation and silver triflate (AgCF₃SO₃) as precursor. The morphological properties of these membranes (PUAg) reveled great dispersion of silver particles, which size was smaller than 110 nm. The propylene solubility in PUAg resulted more than four times superior to the one for the pure PU membrane, revealing the high affinity between silver and propylene. Flory–Huggins theory was more accurate to describe the propylene sorption behavior in PUAg than Henry's model. The ideal solubility selectivity of PUAg membrane resulted 24.4, indicating that there is a good potential for an industrial application aiming at the separation of propylene/propane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42916.