Cross-linked iron oxides

HER2 receptor, which when overexpressed, is associated with breast cancer and stomach cancer Abbreviations CLIO, cross-linked iron oxide CNTs, carbon nanotuhes. 

Abstract CLIO cross-linked iron oxide... 

A novel polysiloxane, containing the isocyanide group pendent to the backbone, has been synthesized. It is observed to react with the metal vapors of chromium, iron and nickel to afford binary metal complexes of the type M(CN-[P])n, where n = 6, 5, 4 respectively, in which the polymer-attached isocyanide group provides the stabilization for the metal center. The product obtained from the reaction with Fe was found to be photosensitive yielding the Fe2(CN-[P])q species and extensive cross-linking of the polymer. The Cr and Ni products were able to be oxidized on exposure of thin films to the air, or electrochemically in the presence of an electron relay. The availability of different oxidation states for the metals in these new materials gives hope that novel redox-active polymers may be accessible. 

Figure 18.16 Hypothetical model for the metallobiology of AP in Alzheimer s disease. (From Bush, 2003. Copyright 2003, with permission from Elsevier.) The proposed sequence of events (1) concentration of iron and copper increase in the cortex with aging. There is an overproduction of APP and AP in an attempt to suppress cellular metal-ion levels. (2) Hyper-metallation of AP occurs which may facilitate H202 production. (3) Hyper-metallated AP reacts with H202 to generate oxidized and cross-linked forms, which are liberated from the membrane. (4) Soluble AP is released from the membrane and is precipitated by zinc which is released from the synaptic vesicles. Oxidized AP is the major component of the plaque deposits. (5) Oxidized AP initiates microglia activation. (6) H202 crosses cellular membranes to react with Cu and Fe, and generate hydroxyl radicals which oxidize a variety of proteins and lipids.

Graft polymerization of monomers such as acrylic acid on core particles consisting of magnetic iron oxide embedded in cross-linked poly (vinyl alcohol) (PVA) has been described previously (2). 

In fact, the polymer is quite stable with respect to precipitation. Once isolated it can be kept in aqueous solution indefinitely (37). This stability is presumably kinetic in origin. Since all evidence points to a different internal structure for the polymer from all crystalline ferric oxide or hydroxide phases, the reorganization required for precipitation would be expected to have a high activation energy. Addition of base to pol5maer solutions does produce an immediate precipitate, presumably by cross-linking the polymer particles. In hydrolyzed ferric nitrate solutions with less than 2.5 base equivalent per mole of iron the eventual precipitates observed are probably formed directly from low molecular weight components. The low rate of dissociation would then be another factor in polymer stability. 

Elastomers of this type are usually cross-linked during fabrication, and often contain fillers such as carbon black or iron oxide to reduce the compliance of the elastomer (i.e. to provide a greater resistance to deformation). Such materials are depicted in Figure 3.1. They are used in technology because of their flexibility and elasticity at low temperatures (-60 °C), their resistance to hydrocarbon solvents, oils, and hydraulic fluids, and their fire resistance.145 For these reasons, they are utilized in aerospace and advanced automotive applications. Some interest exists in their development as inert biomaterials, mainly because of their surface hydrophobicity and consequent biocompatibility. 

An elastomer filled with Aerosil, technical carbon (lamp or acetylene black), iron and titanium oxides and other ingredients including a vulcan-iser is raw rubber used to manufacture various products. The elasticity and resilience of silicone rubbers depend on the number of siloxane links in the chain and on the number of cross links. The higher the molecular weight of the elastomer and its elasticity the more the quantity of cross links (to a certain extent), the greater its mechanical strength. 

Resin Beads. The resin beads are prepared from commercially available Dowex 50W-X8, a sulfonic acid cation exchange resin. The 8% cross-linked resin was chosen because it does not shrink or expand excessively in acid-water systems and because it is readily available. Resin cross-linkage had no detectable effect on the final oxide products in the development test runs. The resin is hydraulically classified to produce a size fraction that is predominately 60-80 m in diameter. The classified resin is washed with 6 M HC1 to remove contaminants such as iron and rinsed thoroughly with water. 

However, the relatively high enzyme costs form an obstacle to commercialization. Inefficient laccase use is a result of its instability towards the oxidizing reaction conditions. We have recently shown that the stability of the laccase under reaction conditions can be improved by immobilization as a cross-linked enzyme aggregate (see Chapter 9). It has also been shown that a water-soluble iron complex of a sulfonated phthalocyanine ligand is an extremely effective catalyst for starch oxidation with hydrogen peroxide in an aqueous medium [11]. 

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