Hydrophilic polymers polysaccharides

With the exception of some linear polysaccharides such as cellulose, polysaccharides are hydrophilic polymers which, in a suitable solvent system, form hydrocolloids with different physical properties. Many polysaccharides are used mainly because of their... 

Despite of hybridization with biological ligands, the general strategy for optimizing protein adsorption on biomaterial surfaces relies on chemical or physicochemical modulation of surface hydrophilicity [38,39]. The common approach is surface immobilization of hydrophilic polymers like polyethylene glycol [PEG] or polysaccharides. Four categories of surface-modification pathways have been developed ... 

Surface-bound, neutral, hydrophilic polymers such as polyethers and polysaccharides dramatically reduce protein adsorption [26-28], The passivity of these surfaces has been attributed to steric repulsion, bound water, high polymer mobility, and excluded volume effects, all of which render adsorption unfavorable. Consequently, these polymer modified surfaces have proven useful as biomaterials. Specific applications include artificial implants, intraocular and contact lenses, and catheters. Additionally, the inherent nondenaturing properties of these compounds has led to their use as effective tethers for affinity ligands, surface-bound biochemical assays, and biosensors. 

Other hydrophilic polymers that could not be retained in water have been separated in aprotic solvents. For example, a variety of polysaccharides have been separated in dimethyl sulfoxide (DMSO), including pullulans, dextrans, various starches, and FicolF. The latter material is a highly branched copolymer of sucrose and epichlorohydrin. Dextrans have been separated in mixtures of water and DMSO. 

It is well known that hydrophilic polymers form a hydrogel that contains excess water [46]. However, the diffusion of molecules and ions in these gels has scarcely been studied due to the lack of suitable methodology. We have found that a tight and elastic polysaccharide solid containing excess water can be used as a solid medium for electrochemical measurements in the same way as liquid water, and that diffusion of molecules and ions takes place in this solid in the same way as in a liquid [47-51]. This allows the solid to be used not only as a medium for electrochemistry, but also as a solid reactor for various chemical reactions. It is of further interest that, in this solid bulk, natural convection does not exist [51], meaning that molecular diffusion can be discriminated from bulk natural convection that should always exist on the earth due to gravity. 

Hydrophilic polymers can be adsorbed onto the capillary surface to generate a neutral semipermanent coating. Examples include polysaccharides. 

Several polymers have been characterized for their ability to form PM and PICM and are presented in Table 4.1. The hydrophilic segment can consist of polysaccharides, such as chitosan. and pullulan, or synthetic polymers, such as poly(ethylene glycol) (PEG), poly(N-vinylpyrrolidone) (PVP), poly(N-isopropylacrylamide) (PNIPAM), poly(2-ethyl-2-oxazoline) and poly(acrylic acid). Of all hydrophilic polymers, PEG (with a molecular weight of 1-20 kD) is undoubtedly the most widely used shell forming component of both PM and PICM. The neutrality, hydrophilicity and flexibility of PEG diminish the possibility of undesirable electrostatic interactions with plasma proteins. Furthermore, the presence of reactive groups at both chain ends... 

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