Relationship between radial diffusion of copper ions released from a metal disk and cytotoxic effects. Comparison with results obtained using extracts

The extended use of metallic biomaterials yields to increasing sources of metal ions within the human body and may result in inflammation of the surrounding tissues, cell damage, and cancer. The aim of this study was to investigate the relationship between the radial diffusion of metal ions released from a metal disk by the corrosion process and the toxic effect on a cell line that grew around it. Results obtained with the metal disks (direct contact) were compared with assays made with extracts obtained from the dissolution of a metallic sample ex situ and then added to the cell culture to elucidate the cause of apparent inconsistencies in previous reports. The change of copper concentration due to corrosion and transient diffusion of copper ions from the copper disks into the cell line was evaluated according to Fick's 2nd law. Surviving cells distribution was interpreted considering the radial and time-dependence of copper concentration. We concluded that the toxic effect on those cells close to metallic biomaterials may be underestimated when only the extract methodology is employed for cytotoxic tests or when during the experiments with disks the presence of concentration gradients and the non-homogeneous distribution of dead cells are disregarded.     

Z2 topological order and the quantum spin Hall effect

The quantum spin Hall (QSH) phase is a time reversal invariant electronic state with a bulk electronic band gap that supports the transport of charge and spin in gapless edge states. We show that this phase is associated with a novel Z2 topological invariant, which distinguishes it from an ordinary insulator. The Z2 classification, which is defined for time reversal invariant Hamiltonians, is analogous to the Chern number classification of the quantum Hall effect. We establish the Z2 order of the QSH phase in the two band model of graphene and propose a generalization of the formalism applicable to multiband and interacting systems.     

Kinetics of the diels–alder addition of ethene to cyclohexa-1,3-diene and its reverse reaction in the gas phase

The addition of ethene to cyclohexa-1,3-diene has been studied between 466 and 591 K at pressures ranging from 27 to 119 torr for ethene and 10 to 74 torr for cyclohexa-1,3-diene. The reaction is of the “Diels–Alder” type and leads to the formation of bicyclo[2.2.2]oct-2-ene. It is homogeneous and first order with respect to each reagent. The rate constant (in l./mol sec) is given by The retron-Diels–Alder pyrolysis of bicyclo[2.2.2]oct-2-ene has also been studied. In the ranges of 548–632 K and 4–21 torr the reaction is first order, and its rate constant (in sec^?1) is given by The reaction mechanism is discussed. The heat of formation and the entropy of bicyclo[2.2.2]oct-2-ene are estimated.     

Searching for new heavy vector bosons inp \bar p colliders

Production and detection of new heavy vector bosons is studied at present (or near future)p \(\bar p\) collider experiments. Application to CERN and Tevatron experiments is considered in detail, but some results for the UNKp \(\bar p\) collider, at \(\sqrt s \) = 6TeV, are also presented. Rather than considering a number of detailed models, we prefer to discuss some general, although necessarily schematic, classes of new vector bosons ranging from strongly interacting Higgs sector models to extended gauge models. We study in particular signals and backgrounds in the \(\ell \overline \ell jj\) channels, where ? are leptons andj are hadron jets.     

Guest-to-host proton transfer in melatonin-beta-cyclodextrin inclusion complex by ionspray, fast atom bombardment and tandem mass spectrometry.

Ionspray (IS) and fast atom bombardment (FAB) positive ionization mass spectrometry (MS) of 1 : 1 beta-cyclodextrin (beta-CD)-melatonin (MLT) host-guest complex allowed the detection of gaseous protonated 1 : 1 beta-CD-MLT. Tandem MS collision-induced dissociation (CID) of such protonated 1 : 1 beta-CD-MLT species showed the proton (charge) to be retained to a significant extent by the host and by its cage fragmentation products, in spite of the higher proton affinity of MLT with respect to that of beta-CD. This requires an endothermic guest-to-host proton transfer to occur within the gaseous association. Collisional activation could be accounted for by the promotion of such an endothermic process; however, the proton affinity decrease of the guest determined by the loss of the elements of acetamide, which is a dominant MS dissociation reaction of pure protonated MLT, could also provide a rationale for such an endothermic guest-to-host proton transfer. This proposal parallels the reaction scheme we had previously formulated for the analogous MS and tandem MS behaviour of 1 : 1 beta-CD-5-methoxytryptamine inclusion complex with the protonated 5-methoxytryptamine guest undergoing deamination.     

Magnetic nanoparticles for a new drug delivery system to control quercetin releasing for cancer chemotherapy

Quercetin belongs to the chemical class of flavonoids and can be found in many common foods, such as apples, nuts, berries, etc. It has been demonstrated that quercetin has a wide array of biological effects that are considered beneficial to health treatment, mainly as anticancer. However, therapeutic applications of quercetin have been restricted to oral administration due to its sparing solubility in water and instability in physiological medium. A drug delivery methodology was proposed in this work to study a new quercetin release system in the form of magnetite?Cquercetin?Ccopolymer (MQC). These materials were characterized through XRD, TEM, IR, and Thermal analysis. In addition, the magnetization curves and quercetin releasing experiments were performed. It was observed a nanoparticle average diameter of 11.5 and 32.5?nm at Fe₃O₄ and MQC, respectively. The presence of magnetic nanoparticles in this system offers the promise of targeting specific organs within the body. These results indicate the great potential for future applications of the MQC to be used as a new quercetin release system.