Kwak Dean, Wu Yuguang, Horbett Thomas A
Department of Chemical Engineering, University of Washington 351750, Seattle, WA 98195, USA.
J Biomed Mater Res A. 2005 Jul 1;74(1):69-83. doi: 10.1002/jbm.a.30365.
Previous studies showed that platelet adhesion to biomaterials from static suspensions was greatly increased by the adsorption of even very small amounts (<5 ng/cm2) of fibrinogen (Fg). In this study, the sensitivity of platelet adhesion to Fg was reexamined by measuring platelet adhesion under flow conditions. The role of adsorbed von Willebrand's factor (vWf) was also studied. Polyethylene (PE) tubing was preadsorbed with Fg, vWf, vWf-deficient plasma, and Fg-deficient plasma or serum with added Fg, and Fg adsorption measured with 125I Fg. Platelets in a red blood cell suspension were passed through the tubes at either low (50 s(-1)) or high (500 or 1000 s(-1)) shear rates and adhesion measured with an improved LDH assay. Adhesion from flowing suspensions measured after preadsorption with afibrinogenemic plasma or serum was very low, but increased greatly with addition of Fg. Less than 10 ng/cm2 of adsorbed Fg was enough to greatly enhance platelet adhesion. Adhesion at high shear was also strongly affected by vWf, as platelet adhesion at 500 s(-1) to PE preadsorbed with vWf-deficient plasma decreased by more than tenfold compared to adhesion at 50 s(-1), but platelet adhesion to PE preadsorbed with normal plasma increased about eightfold when shear rate was increased. The results show that very low amounts of adsorbed Fg are able to support platelet adhesion under shear flow. However, adsorbed vWf also appears to play an important cofactor role in platelet adhesion to biomaterials, as its presence greatly augments platelet adhesion under high shear.
先前的研究表明，即使吸附极少量（<5 ng/cm2）的纤维蛋白原（Fg），血小板从静态悬浮液中黏附到生物材料上的能力也会大幅增强。在本研究中，通过测量流动条件下的血小板黏附情况，重新审视了血小板对Fg黏附的敏感性。同时还研究了吸附的血管性血友病因子（vWf）的作用。用Fg、vWf、缺乏vWf的血浆、缺乏Fg的血浆或添加了Fg的血清对聚乙烯（PE）管进行预吸附，并用125I Fg测量Fg吸附量。将红细胞悬浮液中的血小板以低剪切速率（50 s(-1)）或高剪切速率（500或1000 s(-1)）通过这些管子，并用改进的乳酸脱氢酶（LDH）测定法测量黏附情况。用无纤维蛋白原血症的血浆或血清预吸附后，流动悬浮液中的黏附非常低，但添加Fg后会大幅增加。吸附的Fg少于10 ng/cm2就足以极大地增强血小板黏附。高剪切力下的黏附也受到vWf的强烈影响，因为在500 s(-1)时，血小板对预吸附有无vWf血浆的PE管的黏附比在50 s(-1)时减少了十倍以上，但当剪切速率增加时，血小板对预吸附有正常血浆的PE管的黏附增加了约八倍。结果表明，极少量吸附的Fg能够在剪切流条件下支持血小板黏附。然而，吸附的vWf在血小板与生物材料的黏附中似乎也起着重要的辅助因子作用，因为它的存在极大地增强了高剪切力下的血小板黏附。
