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Covalent Surface Heparinization Potentiates Porous Polyurethane Scaffold Vascularization

Cardiovascular Research Unit, Chris Barnard Division of Cardiothoracic Surgery, Faculty of Health Sciences University of Cape Town, Cape Town, South Africa

^* To whom correspondence should be addressed.

	Abstract

Porous scaffolds play an integral role in many tissue-engineering approaches, and the ability to improve vascularization, without eliciting an excessive inflammatory response, would constitute an important step towards achieving long-term healing and function of devices made from these materials. After having previously optimized the dimensional requirements of the well-defined pores, the present study aimed at a further shift from inflammation to vascularization via surface immobilization with heparin. Porous polyurethane disks were produced to contain well-defined pores (147 ± 2 µm) with abundant interconnecting windows (67 ± 2 µm). After heparinization via copolymer grafting and amination to contain 32 µg of heparin, the modification appeared as a uniform layer on all exposed surfaces, with no signs of pore obliteration or significant changes in pore size. After 28 days implantation in a rat subcutaneous model, the scaffolds were assessed for vascularization/arteriolization and inflammation using CD31/actin and ED-1 staining, respectively. Heparinization resulted in a significant increase in vascularization: capillaries increased by 62% in number (66.2 ± 0.8 to 107.3 ± 1.4 vessels/mm²; p<0.03) and 56% in total area (0.9 ± 0.1 to 1.4 ± 0.02%; p<0.02). Arteriolization also increased in absolute terms (200% in number; p<0.03), but did not change significantly when normalized to capillary number. Heparinization did not significantly affect the inflammatory response at this time-point, as quantified by ED-1 positive macrophage and foreign body giant cell (FBGC) content. Thus, the in vivo vascularization of porous scaffolds could be increased without concomitant increase in the inflammatory response by employing a simple surface modification technique. This could be a valuable tool for in vivo tissue engineering applications where enhanced vascularization is required.

Key Words: angiogenesis, heparin, inflammation, surface modification, scaffold.

First published on November 25, 2008
Journal of Biomaterials Applications 2008, doi:10.1177/0885328208097565


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