Heparin immobilization

Heparin immobilized using the described procedure retained only 1 % of the initial activity of heparin in solution. This fact may probably be explained by the denaturation of heparin effected by nitric acid, which was the reaction medium for the graft-copoly-merization procedure. The inaccessibility of the majority of heparin macromolecules of a copolymer not swelling in an aqueous solution, in particular, supplies... 

Table 17. Results of hemoperfusion through a column containing 865 mg of heparin immobilized in polyacrylamide gel1211...

Other surface modification reactions that are relevant to biological studies include the binding of the blood anticoagulent, heparin,189 and of dopamine190 to polyphosp-hazene surfaces. The heparin immobilization brought about a five-fold increase in the coagulation time of blood, and the immobilized dopamine generated the same response in rat pituitary cells as did free dopamine. 

In order to estimate the release of heparin from the PVC matrix in blood, the amount and the rate of release of heparin from the PVC matrix were examined at 37 °C in physiological saline. Figure 23 shows the release behavior of heparin from PVC films containing heparin-immobilized hydrogels. Too much immobilized heparin in PVC is not well sustained, however, and suitable amounts... 

Table 20. APTT of PVC with heparin-immobilized hydrogels ...

The strategy we adopted in developing thromboresistant, heparin-immobilized surfaces is ... 

Table III. Heparin Immobilization onto Agarose Gels...

Figure 9. APTT vs. spacer unit carbon number results for heparin immobilized via carboxylic groups to diaminoalkane agarose gels. Key —, the baseline APTT (i.e.y unheparinized plasma) , respective control substrate APTT (i.e., untreated diaminoalkane agarose gels) and O, respective heparin immobilized gels.

A more recently developed heparin-polyvinyl alcohol (heparin-PVA) hydrogel (> 70% water) has shown that heparin immobilized via the terminal serine group, which remains on many chains of commercially available heparin, can retain its biological activity in a... 

Park, K.D., Okano, T., Nojiri, C., and Kim S.W. 1988. Heparin immobilized onto segmented polyurethane effect of hydrophillic spacers. /. Biomed. Mater. Res., 22 977-992. 

FIGURE 19.2 Polymeric prostheses for cardiovascular applications, (a) Design (i) and prototype (ii) of a synthetic heart valve fabricated with POSS-PCU nanocomposite polymer, (b) Schematics of an ePTFE vascular graft with heparin immobilized on the surface for anticoagulant effects. Panel (a) Adapted from Kidane et al. [67] with permission from Elsevier, copyright (2009). Panel (b) Adapted from Hoshi et al. [122] with permission from Elsevier, copyright (2013). 

Yoon JJ, Chung HJ, Lee HJ. Heparin-immobilized biodegradable scaffolds for local and sustained release of angiogenic growth factor. J Biomed Mater Res 2006 79 934-42. 

Biomedical Applications. Biomedical applications were investigated by a number of polyphosphazene research groups (181). The most important studies concerned biocompatibility, biodegradation, enz5une immobilization, and drug delivery (182,183). Polyphosphazene implants and prosthe-ses were also examined. Biocompatibility through appropriate manipulation of surface or bulk chemistry was studied extensively (184). Works on the synthesis and cross-linking of amphiphilic polyphosphazenes (94), heparin immobilization (185-187), and other surface functionalizations (4,101) were reported. 

Aksoy E A, Hasirci V, Hasirci N, Motta A, Fedel M, Migliaresi C. Plasma protein adsorption and platelet adhesion on heparin-immobilized polyurethane films. J Bioact Compat Polym 2008 23 505-19. 

Park KD, Okano T, Nojiri C, Kim SW. Heparin immobilization onto segmented polyure-thaneurea surfaces—effect of hydrophilic spacers. J Biomed Mater Res 1988 22 977-92. http //dx.doi.Org/10.1002/jbm.820221103. 

Han DK, Park KD, Ahn KD, Jeong SY, Kim YH. Preparation and surface characterization of PEO-grafted and heparin-immobilized polyurethanes. J Biomed Mater Res 1989 23 87-104. 

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