Osmium-containing polymers

The osmium-containing polymers can also be used for the mediated reduction of N02 to produce NO+ [96]. Rotating-disk voltammetry shows that for... 

The examples described in this chapter clearly show the potential of modified electrodes based on redox-active osmium-containing polymers. The redox potentials of these materials can be manipulated by varying the nature of the polymer-bound redox couple, which allows us to tailor polymers to particular application, especially in the sensors area. Furthermore changes can also be made in the polymer composition both with respect to polymer loading and the nature of the polymer backbone. This will allow control of such parameters as substrate diffiision and charge transport through the layer. This flexibility allows the systematic investigation of electrochemical properties of electrodes modified with such materials. 

In the past decade, much work has been done on the exploration and development of redox polymers that can rapidly and efficiently shuttle electrons. Several research groups have wired the enzyme to the electrode with a long chain polymer having a dense array of electron relays. The polymer penetrates and binds the enzyme to the electrode. Gregg and Heller have done extensive work on osmium-containing polymers. They have made a large number of such polymers and evaluated their electrochemical characteristics [14]. Their most stable reproducible redox polymer was poly(4-vinyl pyridine) to which Os(bpy)3Cl2... 

CHARGE TRANSPORT PROPERTIES OF ELECTRODES MODIFIED WITH OSMIUM CONTAINING POLYMER FILMS,... 

Charge Transport Properties of Electrodes Modified with Osmium Containing Polymer Films R.J. Forster and J.G. Vos... 

Pishko MV, Katakis I, Lindquist SE, Ye L, Gregg BA, Heller A. 1990. Direct electron exchange between graphite electrodes and an adsorbed complex of glucose oxidase and an osmium-containing redox polymer. Angew Chem 102 109-111. 

A BASJ ion-exchange microbore column (45 cm x 1 mm i.d.) 0.05 Sodium phosphate buffer of pH 8.5 containing 0.1 mM EDTA [60 pL/min]. Electrochemical at horseradish peroxidase osmium redox polymer-modified vitreous C electrodes at 0 mV versus Ag/AgCl. Rat frontal cortex dialysate samples [188]... 

Figure 6.14 Components of an osmium containing redox hydrogel used to immobilize enzymes at electrode surfaces. Typically m = 1.2, n = 4, p = 1, and <7 = 10. Cross-links between the redox polymer chains are formed by reaction between the water-soluble diepoxide and amine groups on the polymer chains. (Adapted from [118] and [123].)...

FIGURE 9.18. Components of an osmium containing redox hydrogel. The basic polymer is derived from Fig. 9.17, with n = 1, m = 4, and p = 1.2. The polymer is cross-linked using the water-soluble diepoxide according to the reaction shown (see Ref. 111). 

Polymers containing benzimidazole units in their backbones have also been used in the synthesis of coordination metallopolymers (159-162). Osmium and ruthenium coordinated polymers with bipyridine ligands have been prepared (159,160). These polymers (72, 73) possessed metal-metal interactions through their conjugated backbones. Communication between the ruthenium centers of 72 increased by deprotonating the imidazole protons (160). The osmium coordinated polymer (73) showed two reduction waves separated by 0.32 V, indicative of strong cnmmimication between the Os centers (159). 

Figure 5. Dependence of current density on hydrogen peroxide concentration for cathodes based on different peroxidases, (open circles) NaI04 treated horseradish peroxidase (closed circles) native horseradish peroxidase (open squares) lactoperoxidase (closed squares) Aithromyces ramosus. Each electrode contains approximately 10/ g osmium redox polymer, polyethylene glycol diglycidyl ether crosslinker and 1 to 4/

Electrochemical reduction of ruthenium and osmium complexes containing /ra i-chloride ligands leads to metal-containing polymers in which metal-metal bonds make up the entire polymer backbone. Hence, reduction of [M (tran5-Cl2) (bipy)(CO)2l (M=Ru, Os) (77) to M complexes generated a polymeric film (78) after loss of the chloride ligands (Scheme 23). Both the ruthenium- and osmium-based coordination polymers were selective for the reduction of carbon dioxide to carbon monoxide and formate. 

The tin, iron, and osmium examples discussed above allow one to imagine all sorts of possibilities for metal- and metalloid-containing polymers with biomedical applications. In the next section a series of selected biomedical applications of metal-bound polymers is reviewed. This is followed by a short review of some representative small molecules containing metals which have biomedical uses. 

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