Surface-bound hydrophilic polymers, steric

Steric Repulsion with Surface-Bound Hydrophilic Polymers... 

It should be mentioned that the surface-bound hydrophilic polymer brushes may prevent adsorption of foulants onto membrane surface because of the steric repulsion mechanism [31]. When hydrophilic polymer chains are created on membrane surfaces, this diffuse hydrophilic layer will exert steric repulsion on the foulant that reaches the surface (Figure 18.2c). Extent of steric repulsion depends on the density, length, and regularity of grafted or deposited polymer brushes [32,33]. 

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. 

Surface modification with hydrophilic polymers, such as poly(ethylene oxide) (PEO), has been beneficial in improving the blo( compatibility of polymeric biomaterials. Surface-bound PEO is expected to prevent plasma protein adsoiption, platelet adhesion, and bacterial adhesion by the steric repulsion mechanism. PEO-rich surfaces have been prepared either by physical adsorption, or by covalent grafting to the surface. Physically adsorbed PEO homopolymers and copolymers are not very effective since they can be easily displaced from the surface by plasma proteins and cells. Covalent grafting, on the other hand, provides a permanent layer of PEO on the surface. Various methods of PEO grafting to the surface and their effect on plasma protein adsorption, platelet adhesion, and bacterial adhesion is discussed. 

In this article, we will discuss the steric repulsion of plasma proteins, platelets, and bacteria by surface-bound poly(ethylene oxide) (PEO). PEO, a neutral hydrophilic polymer, has been used most widely for surface modification of biomaterials. 

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