Department of Mechanical and Industrial Engineering, Northeastern University, 334 Snell Engineering Center, 360 Huntington Avenue, Boston, MA 02115-5000, USA.
Mater Sci Eng C Mater Biol Appl. 2013 Jul 1;33(5):2770-5. doi: 10.1016/j.msec.2013.02.042. Epub 2013 Mar 1.
Surface defects, blood flow shear rates and mechanical stresses are contributing factors in the calcification process of polymeric devices exposed to the blood flow. A number of experiments were performed to evaluate the effect of surface defects such as roughness and cracks and flow shear rate on the calcification process of a polyurethane material used in the design of prosthetic heart valves. Results showed that polyurethane surface gets calcified and the calcification is more pronounced at the lower shear rates. Roughness and cracks both increase the calcification levels. The results also suggest very little diffusion of calcium to the subsurface indicating that calcification of a polyurethane material, is a surface phenomenon. Based on a simple peeling test, the bond strength between the calcified layer and polyurethane was found to be extremely weak, suggesting that the bonding is in the form of Van-der-Waals. A limited set of experiments with polycarbonate showed that polycarbonate is less prone to calcification compared to polyurethane (p values less than 0.05), indicating its potential application in medical devices exposed to blood flow.
表面缺陷、血流切变率和机械应力是暴露于血流中的聚合体装置钙化过程的促成因素。进行了多项实验来评估表面缺陷（如粗糙度和裂纹）和流动切变率对用于人工心脏瓣膜设计的聚氨酯材料钙化过程的影响。结果表明，聚氨酯表面发生钙化，在较低的切变率下钙化更为明显。粗糙度和裂纹都会增加钙化程度。结果还表明，钙很少扩散到次表面，表明聚氨酯材料的钙化是一种表面现象。基于简单的剥离试验，发现钙化层与聚氨酯之间的结合强度非常弱，表明结合形式为范德华力。一组有限的聚碳酸酯实验表明，与聚氨酯相比，聚碳酸酯不易发生钙化（p 值小于 0.05），表明其在暴露于血流的医疗器械中的潜在应用。
