Polyurethane Surface modification techniques

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. 

Interest continues in the binding of heparin to polymers in an attempt to produce non-thrombogenic surfaces. This has been the aim in the use of glutaralde-hyde-protein complexes as coatings for latex rubber and polyurethanes. Glutaraldehyde has also been used to bind antibodies to partially hydrolysed polyamide surfaces for enzyme-linked radioassay techniques. One of the few examples of direct polymerization (as opposed to surface modification) in an attempt to produce polymers having improved compatibility involves the use of 2-methacryloyloxyethylphosphoryl choline in the formation of homopolymers and copolymers with methyl methacrylate. An isocyanato-urethane methacrylate has been synthesized from 2-hydroxyethyl methacrylate in connection with dental materials research in which the preparation of poly functional monomers for improvement of interfacial bonding with tooth tissue is a topic of some interest. 

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