Toxic trace elements at gastrointestinal level

Many trace elements are considered essential [iron (Fe), zinc (Zn), copper (Cu)], whereas others may be harmful [lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As)], depending on their concentration and chemical form. In most cases, the diet is the main pathway by which they enter our organism. The presence of toxic trace elements in food has been known for a long time, and many of the food matrices that carry them have been identified. This has led to the appearance of legislation and recommendations concerning consumption. Given that the main route of exposure is oral, passage through the gastrointestinal tract plays a fundamental role in their entry into the organism, where they exert their toxic effect. Although the digestive system can be considered to be of crucial importance in their toxicity, in most cases we do not know the events that occur during the passage of these elements through the gastrointestinal tract and of ascertaining whether they may have some kind of toxic effect on it. The aim of this review is to summarize available information on this subject, concentrating on the toxic trace elements that are of greatest interest for organizations concerned with food safety and health: Pb, Cd, Hg and As.     

Structural Behavior of Cylindrical Polystyrene‐block‐Poly(ethylene‐butylene)‐block‐Polystyrene (SEBS) Triblock Copolymer Containing MWCNTs: On the Influence of Nanoparticle Surface Modification

In this work, the influence of carbon nanotubes (CNTs) on the self‐assembly of nanocomposite materials made of cylinder‐forming polystyrene‐block‐poly(ethylene‐butylene)‐block‐polystyrene (SEBS) is studied. CNTs are modified with polystyrene (PS) brushes by surface‐initiated atom transfer radical polymerization to facilitate both their dispersion and the orientation of neighboring PS domains of the block copolymer (BCP) along modified CNT‐PS. Dynamic rheology is utilized to probe the viscoelastic and thermal response of the nanoscopic structure of BCP nanocomposites. The results indicate that nonmodified CNTs increase the BCP microphase separation temperature because of BCP segmental confinement in the existing 3D network formed between CNTs, while the opposite holds for the samples filled with modified CNT‐PS. This is explained by severely retarded segmental motion of the matrix chains due to their preferential interactions with the PS chains of the CNT‐PS. Moreover, transient viscoelastic analysis reveals that modified CNT‐PS have a more pronounced effect on flow‐induced BCP structural orientation with much lower structural recovery rate. It is demonstrated that dynamic‐mechanical thermal analysis can provide valuable insights in understanding the role of CNT incorporation on the microstructure of BCP nanocomposite samples. Accordingly, the presence of CNT has a significant promoting effect on microstructural development, comparable to that of annealing.     

Plasticization and antiplasticization of an acrylic pressure sensitive adhesive by ibuprofen and their effect on the adhesion properties

In transdermal patches, an unpredictable alteration of the mechanical behavior of the pressure sensitive adhesive (PSA) can occur if a drug is added. In the present study, the suitability of Dynamic Mechanical Analysis (DMA)/Dynamic Mechanical Thermal Analysis (DMTA) as methodologies to detect the change in adhesion properties caused by the addition of an API was examined. With DMA/DMTA, time- and temperature-dependent viscoelastic properties were determined. Tack and shear adhesion of blends of the acrylic adhesive DuroTak® 87-4287 and ibuprofen at increasing concentrations were investigated. Interestingly, the probe tack test showed highest values at 1% ibuprofen concentration in the PSA and decreasing values with increasing ibuprofen concentrations. The shear adhesion of the PSA was decreased at all investigated ibuprofen concentrations. With DMA/DMTA, it could be demonstrated that antiplasticization and plasticization are responsible for the change in tack. The main reason for the decrease in shear adhesion is a shift of the T_g to lower temperatures, while antiplasticization only has a marginal effect. The term “antiplasticizing space” was introduced because antiplasticization depends on time, temperature, stress, strain, and API concentration. In general, this antiplasticizing space can have an impact on processing, stability, and in vivo behavior of API/polymer blends in drug formulations.     

热塑性淀粉/乙烯-乙烯醇共聚物复合材料的制备与性能

利用熔融共混的方法,制备得到热塑性淀粉/乙烯-乙烯醇共聚物（TPS/EVOH）复合材料,并对该复合体系的加工性能、机械性能、动态力学性能、流变性能以及吸水性进行了研究.结果表明：随着EVOH含量增加,复合材料中分子间作用力加强;复合体系的机械性能得到改善;当EVOH含量到达30%后,复合材料的吸水性明显降低.     

Comparative Analysis of Polyurethane Drive Belts with Different Cross-Section Using Thermomechanical Tests for Modeling the Hot Plate Welding Process

The paper presents a comparative analysis of the circular and flat cross-section belts using measurements of a set of thermomechanical parameters, contributing to research about hot plate welding of drive belts. On the basis of thermogravimetric and spectrophotometric tests, information about the same chemical composition of the two belts was obtained. Dynamic thermomechanical analysis and scanning differential calorimetry provided information about a small difference between belts, which disappeared when the material was placed in a state of increased temperature and mechanical stress. On the basis of the analysis of the specific heat, thermal diffusion, density, and hardness, the values of the selected thermal properties of the belt were obtained, and a large similarity between the belts was identified. On the basis of the novel performed test cycle, it has been hypothesized that circular and flat belts made from thermoplastic polyurethane elastomer could be used interchangeably for butt-welding testing. It has also been proven that cyclic thermomechanical loads unify the properties of both materials so that multiple mechanical and thermal loads do not result in any change in the material properties of the two belts. As a consequence, changes in the weld properties after welding, compared to a solid belt, are not expected.     

Analysis of Thermomechanical Properties of Polyethylene with Cement Addition

The paper undertakes preliminary research towards the identification of the use of plastic waste, taking into account the possibility of increasing their mechanical strength and reducing flammability, as well as reducing the emission of harmful compounds to the atmosphere through the addition of cement. This is extremely important not only from the point of view of the wide use of plastic products in the industry, but also their thermal utilization. The present study deals with the aspect of the utilization of waste polyethylene (HDPE) as a matrix in composites with filler in the form of cement at 5 and 10%. The composite samples were prepared by injection molding after the prior proper mixing of the components. Comparative thermomechanical (DSC, tensile strength, DMTA), microstructure and flammability results are presented for HDPE samples and their composites with cement. It was found that the addition of cement as a filler to polyethylene made it possible to obtain composites with good thermomechanical properties.     

Structural analogs of 5'-methylthioadenosine as substrates and inhibitors of 5'-methylthioadenosine phosphorylase and as inhibitors of human lymphocyte transformation

5'-Deoxy-5'-methylthioadenosine (MTA) phosphorylase was purified 13.4-fold from human peripheral lymphocytes. The enzyme demonstrated normal Michaelis-Menten kinetics with Km values of 26 microM and 7.5 mM for the two substrates, MTA and phosphate, respectively. The rate of MTA degradation was temperature dependent, 47 degrees being the optimum temperature. Five structural analogs served as alternative substrates with Km values ranging from 31 to 53 microM while two compounds, 5'-deoxy-5'-methylthiotubercidin (MTT) (Ki = 31 microM) and adenine (Ki = 172 microM), were inhibitory. These same analogs were examined as inhibitors of mitogen-induced human lymphocyte blastogenesis. MTT was found to be the most effective inhibitor of lymphocyte transformation with an I50 of 80 microM.     

Thiol‐ene Hybrid Organic/Inorganic Nanostructured Coatings Based on Thiol‐Functionalized Zirconium Oxoclusters

The thiol‐functionalized zirconium oxocluster Zr₁₂(µ₃‐O)₈(µ₃‐OH)₈(MP)₂₄ · 4MPA was used as inorganic nanosized building block in the thiol‐ene photopolymerization of APE and TH in a 1:1 molar mixture. Transparent and crack‐free coatings were obtained, and TEM analysis showed that the inorganic particles are well dispersed within the polymeric network with no significant macroscopic agglomeration. An increase of T_g values, storage modulus in the rubbery region, and thermal stability were evidenced by increasing the zirconium oxocluster content in the photocurable formulations. XPS analysis and SIMS depth profile were carried out on UV cured films and showed the presence of a homogeneously distributed zirconium oxocluster.