Surface properties of polyurethane biomaterials

Tremendous efforts have been put into surface modification of polyurethane biomaterials to promote cell adhesion [41] and/or depress platelet adhesion [42,43], biofihn formation [44], or protein adsorption [45]. CA is the quickest indirect evidence of confirming these surface modifications. Cooper et al. [41] prepared a series of polyurethanes with surfaces functionalized with three hexapeptides to improve cell adhesion. The polar peptides on the surface increase the hydrophilicity and thus decreased CAs were observed. Again, CA is only an indirect proof of a successful surface modification since there are many factors that contribute to a change in CA. Many other surface characterization techniques must be combined to obtain a fuU picture of the surface properties of polyurethane biomaterials. 

The surface properties of polyurethane biomaterials are so important that they cannot be overemphasized and there have been many innovative ways to tailor polyurethanes interfaces. In this chapter, we discussed some important but not all surface... 

Sagnella S, Mai-Ngam K. Chitosan based surfactant polymers designed to improve blood compatibility on biomaterials. Colloids SurfB Biointerfaces May 2005 42(2) 147-55. Wang Y, Hong Q, Chen Y, et al. Surface properties of polyurethanes modified by bioactive polysaccharide-based polyelectrolyte multilayers. Colloids Surf B Biointerfaces December 2012 100 77-83. 

Polyurethanes were first suggested for use as biomaterials in 1967 [36]. Polyurethane materials have excellent mechanical properties, making them suitable for many different biomedical applications. Currently, a variety of polyurethanes are used in biomedical devices like coatings for catheters and pacemaker leads (Table A.2). The biocompatibility of biomedical polyurethanes appears to be determined by their purity i.e., the effectiveness of the removal from the polymer of catalyst residues and low molecular weight oligomers [37]. The surface properties of commercially available polyurethanes, which are critically important in determining biocompatibility, can vary considerably, even among lots of the same commercially available preparation [38]. 

Lin, H.-B., et al., Surface properties of RGD-peptide grafted polyurethane block copolymers Variable take-off angle and cold-stage ESCA studies. Journal of Biomaterial Science Polymer Edition, 1993, 4(3), 183-198. 

Tan J, Brash JL. Nonfouling biomaterials based on polyethylene oxide-containing amphiphilic triblock copolymers as surface modifying additives synthesis and characterization of copolymers and surface properties of copolymer-polyurethane blends. J Appl Polym Sci 2008 108 1617-28. 

Bacterial adhesion is the altical step in the pathogenesis of biomaterial-associated infection and is critically inflnenced by numerous variables including surface properties of biomaterials, the nature of the environment, and the bacterial cell surface. In addition, adsorbed proteins play an important role in bacteria-surface interactions. One strategy for the development of antibacterial polyurethanes has focused on... 

The importance of surface enrichment in the determination of copolymer surface properties is demonstrated by a number of surface analysis studies of polyurethanes [22,27-29], The versatility of polyurethanes as biomaterials is derived from the ability to control physicochemical and biological properties of the material by altering the proportions of hard and soft segments. 

Morimoto N, Iwasaki Y, Nakabayashi N, Ishihara K. Physical properties and blood compatibility of surface-modified segmented polyurethane by semi-interpenetrating polymer networks with a phospholipid polymer. Biomaterials 2002 23(24) 4881-7. 

Lin DT, Young TH, Fang Y. Studies on the effect of surface properties on the biocompatibility of polyurethane membranes. Biomaterials 2001 22(12) 1521-9. 

Polytetrafluoroethylene, polyurethanes, polyethylene, silicones and acrylates have been proposed for replacement of both hard and soft tissues. These biomaterials must satisfy two in5)ortant criteria to provide an useful function in a biological environment they should possess the proper physical characteristics as replacement materials and should exhibit compatible interfacial properties with surroimding tissues and fluids. The interaction of blood with foreign surfaces resulting in thrombogenesis has received considerable attention, but still represents a problem. 

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