Applications of advanced polymers in medicine: Bioartificial polymeric materials

A new class of biornaterials, called "bloartificial polymeric materials", was prepared blending fibrinogen (FBNG) with a segmented polyurethane (PU), and collagen (CLG) with poly(acrylic acid) (PAA), poly(acrylamide) (PAAM) , poly(vinyl alcohol) (PVAL) respectively. The PU-FBNG rna terial was processed through a phase-inversion, spraying technique to fabricate porous vascular grafts. FBNG was subsequently converted into covalently cross-linked fibrin (FBN) through the action of thrombin (Th), fibrin-stabilizing factor (FSF), and calcium ions. Cross-linked blend resulted in a higher thermal stability with respect to native cross-linked FBN. Tensile behaviors of PU-FBN materials closely matched those of a natural artery by varying the ratio PU/FBN. In vivo experiments showed a better neointima formation and tissue ingrowth for PU-FBN(50%) grafts in comparison of PU grafts. However, 50% of FBN did not assure adequate mechanical resistence, and aneurysmal changes were seen in some grafts . CLG-based materials, processed by casting, showed a consistent protective effect of the synthetic component with respect to CLG denaturation temperature, particularly noticeable for CLG-PAA and CLG-PVAL blends. Materials advantages and drawbacks are discussed.