Polyelectrolytes, stabilization

Perrin P, Monfreux N, Lafuma F. Highly hydrophobically modified polyelectrolytes stabilizing macroemulsions relationship between copolymer structure and emulsion type. Colloid Polym Sci 1999 277 89-94. 

G.S. Nahor, S. Mosseri, P. Neta, and A. Harriman, Polyelectrolyte-Stabilized Metal Oxide Hydrosols as Catalysts for the Photooxidation of Water by Zinc Porphyrins, J. Phys. Chem., 92 (1988) 4499. 

The process of adsorption of polyelectrolytes on solid surfaces has been intensively studied because of its importance in technology, including steric stabilization of colloid particles [3,4]. This process has attracted increasing attention because of the recently developed, sophisticated use of polyelectrolyte adsorption alternate layer-by-layer adsorption [7] and stabilization of surfactant monolayers at the air-water interface [26], Surface forces measurement has been performed to study the adsorption process of a negatively charged polymer, poly(styrene sulfonate) (PSS), on a cationic monolayer of fluorocarbon ammonium amphiphilic 1 (Fig. 7) [27],... 

N. A. Okishev, A. G. Ivanov, and I. V. Karpenko. Plugging solution for oil and gas wells with increased sedimentation stability—containing Portland cement, nitrile trimethyl phosphonic acid, polyoxyethylene, water-soluble cationic polyelectrolyte and water. Patent RU 2039207-C,1995. 

Poly(N-phenyl-3,4-dimethylenepyrroline) had a higher melting point than poly(N-phenyl-3,4-dimethylenepyrrole) (171° vs 130°C). However, the oxidized polymer showed a better heat stability in the thermogravimetric analysis. This may be attributed to the aromatic pyrrole ring structures present in the oxidized polymer, because the oxidized polymer was thermodynamically more stable than the original polymer. Poly(N-phenyl-3,4-dimethylenepyrroline) behaved as a polyelectrolyte in formic acid and had an intrinsic viscosity of 0.157 (dL/g) whereas, poly(N-pheny1-3,4-dimethylenepyrrole) behaved as a polyelectrolyte in DMF and had an intrinsic viscosity of 0.099 (dL/g). No common solvent for these two polymers could be found, therefore, a comparison of the viscosities before and after the oxidation was not possible. 

Buffer salts also can exert a secondary salt effect on drug stability. From Table 5 and Fig. 5 it is clear that the rate constant for an ionizable drug is dependent on its pKa. Increasing salt concentrations, particularly from polyelectrolytes such as citrate and phosphate, can substantially affect the magnitude of the pKa, causing a change in the rate constant. (For a review of salt effects, containing many examples from the pharmaceutical literature see Ref. 116.)... 

It should be pointed out that the addition of substances, which could improve the biocompatibility of sol-gel processing and the functional characteristics of the silica matrix, is practiced rather widely. Polyethylene glycol) is one of such additives [110— 113]. Enzyme stabilization was favored by formation of polyelectrolyte complexes with polymers. For example, an increase in the lactate oxidase and glycolate oxidase activity and lifetime took place when they were combined with poly(N-vinylimida-zole) and poly(ethyleneimine), respectively, prior to their immobilization [87,114]. To improve the functional efficiency of entrapped horseradish peroxidase, a graft copolymer of polyvinylimidazole and polyvinylpyridine was added [115,116]. As shown in Refs. [117,118], the denaturation of calcium-binding proteins, cod III parvalbumin and oncomodulin, in the course of sol-gel processing could be decreased by complexation with calcium cations. 

Encapsulation via the layer-by-layer assembly of multilayered polyelectrolyte (PE) or PE/nanoparticle nanocomposite thin shells of catalase in bimodal mesoporous silica spheres is also described by Wang and Caruso [198]. The use of a bimodal mesoporous structure allows faster immobilization rates and greater enzyme immobilization capacity (20-40 wt%) in comparison with a monomodal structure. The activity of the encapsulated catalase was retained (70 % after 25 successive batch reactions) and its stability enhanced. 

On the basis of the knowledge that different polyelectrolytes can stabilize proteins [180], even in water-organic mixtures [181], it was important to check the membraneforming polyelectrolyte itself as a potential stabilizer. Indeed, as was found from spec-trophotometric investigations, Nation stabilizes glucose oxidase suspensions in organic solvents. 

Suspending enzyme in polymer solution instead of in pure organic solvent not only simplifies preparation of the casting solution, the enzyme suspensions became more uniform and stable. It was also found that at certain concentrations (enzyme, polyelectrolyte, and water) the resulting membranes exhibited extremes in both stability and... 

N.A. Chaniotakis, Enzyme stabilization strategies based on electrolytes and polyelectrolytes for biosensor applications. Anal. Bioanal. Chem. 378, 89-95 (2002). 

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