Polymer surface, heparin covalently

Ikada and coworkers also studied the blood compatibility and protein denaturation properties of heparin covalently and ionically bound onto polymer surfaces [513], Both types of bound heparin gave deactivation of the coagulation process. Clotting deactivation was attributed to a heparin/ antithrombin III complex by covalently bound heparin which gave adsorbed protein denaturation and platelet deformation as compared with lack of these features with ionically bound heparin. 

A method of covalently bonding heparin to a polymer substrate is presented. The synthetic route consists of coupling heparin covalently with polyisocyanatostyrene. This reaction was made possible by the fact that formamide is a room temperature solvent for sodium heparin and this allowed a liquid-solid interface reaction to take place. Lee-White clotting tests in vitro (in hydrogel tubes) showed these surfaces to be non-clotting after 24 hours whereas untreated controls and surfaces of GBH type clotted in approximately 25-35 minutes. 

Dincer, A. K., Sc. D. Thesis, "Covalent Coupling of Heparin to Synthetic Polymer Surfaces", MIT, 1977. 

Another commercially available coating uses the anticoagulant heparin. Heparin coatings have two different mechanisms of imparting hemocompatibility. Heparin-releasing surfaces slowly release bound heparin, in an effective but impermanent route to hemocompatibility 19). Another way of utilizing heparin is to inunobilize the molecule by covalent linkage with the polymer surface 19, 20). 

In the present contribution different covalent coating procedures will be reviewed and described (Fig.l).- For ES-HS and heparin, this results in different thickness of nanocoatings and different attachment to polymer surfaces. 

Polymer linker can be used to conjugate nanoparticles to the surface of islets. One example is a heterofunctional PEG-mediated conjugation method by covalent-linkage [91]. The chemical conjugation was mediated by a heterobifunctional PEG polymer, maleimide-PEG-N-hydroxysuccinimide ester (NHS), which is biocompatible with blood, cell, and tissue. The maleimide group of the PEG polymer can react with the sulfhydryl group of the heparinized superparamagnetic... 

Chitosan-heparin coated polymers display excellent thrombo-resistance properties. The lifetime of the thromboresistance can be extended by covalently binding the heparin to chitosan with the aid of sodium cyanoborohydride. This surface treatment is useful for biomedical applications requiring blood compatibility for periods as long as four days. 

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