抗凝血聚氨酯材料的研究进展

聚氨酯由于其优良的抗凝血性能和良好的物理机械性能而成为目前研究和应用最广的一种生物医用高分子材料。本文就嵌段型聚氨酯、拦枝型聚氨酯、离子型聚氨酯及其它具有良好发展前景的聚氨酯抗凝血材料的研究进展作扼要综述。     

Antithrombic activity of some polysaccharide resins

Crosslinked dextrans (Sephadex®) bearing essentially car☐ymethyl, benzylsulphonate and -amino acid groups have been synthesized. The antithrombic activity of the resins may be the result of a cooperative effect between the functional groups. The binding of benzylsulphonate to car☐ymethylated Sephadex endows these materials with activity. However the highest activity is obtained when the resins contain simultaneously benzylsulphonate, -amino acid and car☐ylic acid groups.     

抗凝血高分子

本文就便于短期应用的高分子负栽型抗凝血材料、具有良好发展前景的亲水—疏水型材料及杭凝血高分子材料中的微观相分离结构问题的研究进展,进行了扼要综述。     

A survey of surface hemorheological experiments on the inhibition of fibrinogenin formation employing surface layers of fibrinogen systems with heparins and other substances. A contribution on antithrombogenic action

In earlier studies using a modified Weissenberg Rheogoniometer, we found decreased rigidity or torque values (tau) in surface layers of heparin plasma, when compared to tau of oxalate plasma from the same blood withdrawal (Thrombosis Res. 1, 1-17, 1972). In subsequent studies of the viscoelasticity of surface layers of highly purified fibrinogen (97-100% clottability) of human and bovine origin, we found, with some heparins, marked lowering of surface viscous moduli (eta's) and of surface elastic moduli (Gs). With some heparins no changes in tau, eta's and Gs occurred. Certain low molecular weight (LMW) preparations of heparins showed decreases, but some did not. This is also the case with heparins of low and high affinity for antithrombin. Calcium heparin and Ca2+ alone always increased eta's and Gs, when added to the fibrinogen system. N-desulfated heparin both decreased or did not change eta's and Gs. Preparations of fibrinogen in dog plasma, to which sodium heparin was added, resulted in a decrease of tau values. These results appear to emphasize that plasma proteins other than fibrinogen, and other plasma constituents, may affect surface hemorheological values. These findings suggest needed interface studies of fibrinogen systems to which plasma or plasma constituents are added. We found also that other substances, i.e., dextran MW 20,000; dextran sulfate MW 17,000; sodium hyaluronate and depolymerized hyaluronate decreased tau, eta's and Gs markedly. Recent findings in the literature are discussed in relation to thrombogenesis in which fibrinogenin gelation is considered as the initial phase of blood clotting. Fibrinogenin is the new term for initial fibrinogen aggregation and subsequent fibrinogen gelation without thrombin participation. The inhibition of fibrinogenin formation extra vivum is considered to be a valid indicator of antithrombogenic activity of substances which play a significant role in investigations on the therapy and prevention of thrombotic conditions.     

A natural rubber drainage tube with antithrombogenic lumen surface

A drainage tube was made by radiation vulcanization of a high polymeric substance based on natural rubber elastomers. Pentosan polysulphate sodium bound to a carrier substance (synthetic type 4A or 13X zeolite) was incorporated in the drainage tube which was then tested for its anticoagulant properties during perfusion with Tris buffer solution, citrated plasma, and blood, resp. The amount of pentosan polysulphate sodium released from the tube walls during perfusion with human citrated plasma in an open circulatory system was sufficient to exert an anticoagulant effect on the streaming plasma. This effect was corroborated by prolonged thrombin times and by unclottability in case of recalcified plasma samples in thrombelastographic studies. The antithrombogenicity test according to Chandler in a closed circulatory system revealed thrombus formation times (TFT) of more than 24 h (control: TFT = 1–3 min in native blood).     

Chronic Antithrombogenic Biomaterials Screen

The widespread usage of chronic implantable sensors in cardiac device systems has been hampered by both sensor technology issues and the lack of surface passivations with chronic antithrombogenic capabilities. In this study, dummy pacing leads with six types of passivations were implanted for 17 weeks in 36 dogs to assess thrombogenic character, degree of tissue growth and encapulation, and general performance in providing optically clear windows into the blood or body tissues. Asceptic surgical procedures were used and complete blood work-up was performed every two weeks postop. Two dogs served as surgical shams to monitor system artifacts. At explant the devices fairly clearly divided themselves into two groups based on the percent of exposed surface area covered by gross macroscopic tissue accumulations. There were three passivated types in each group. Scanning election microscopy (SEM) and energy dispersive analysis of x-rays (EDAX) techniques were used to investigate further the samples from the three passivation types that performed "better" based an percent surface area analysis. Issues that became prominent were substrate surface finish and topography, and some mineralization phenomena. Some of the evidence raises The possibility that processes that provide chronic antithrombogenic performance might also enhance mineralization or propensity toward natural breakdown processes. These questions are now being more closely addressed in follow-up studies now in progress.