Micro-machining of microcirculation model and a method for analyzing deformability and fluidity of blood cells

采用透明微通道流动系统分析红细胞的可变形性和流动性，并采用原子力显微镜（AFM）分析细胞膜的微观弹性，分别测定了红细胞和血小板在糖尿病和其他物理化学条件下的力学性能。采用石英玻璃板作为微通道流动系统的毛细管模型。采用硅微加工技术，在玻璃板上直接切割出50条狭窄沟槽的流道。将克雷布斯-林格溶液倒入流动系统中调节血细胞悬液的浓度。施加10 ~ 30 cmH_2O静水压力，使血流顺利通过通道。在活体显微镜下观察血细胞的局部图像，用高速摄像机记录，用PC基图像处理器分析。在接触模式下使用AFM，给出了AFM悬臂梁挠度与位移的关系。用胡克定律和赫兹模型分别对力曲线数据进行了弹簧常数和杨氏模量的估计。结果表明，糖尿病红细胞的变形能力明显低于健康对照，特别是在高剪切速率下。糖尿病红细胞的弹性常数和杨氏模量明显高于正常人。这些红细胞在毛细血管流动通道中明显硬化，不易变形，可能与微血管病变的生长有关。糖尿病血小板黏附、聚集倾向增强，血栓形成加速。提示微血管内皮细胞层可能容易受到损伤，导致血小板在短时间内形成血栓。

Mechanical properties of erythrocyte and blood platelet under diabetic and some other physico-chemical conditions were measured by using transparent micro-channel flow system to analyze the blood cell deformability and fluidity, and also by using atomic force microscope (AFM) to analyze microscopic elasticity of the cell membrane respectively. The micro-channel flow system was made of quartz glass plate and used as a capillary model. Flow channels of 50narrow ditches were straight cut on the glass plate by means of silicon micro-machining technology. Concentration of blood cell suspensions was adjusted with Krebs-Ringer solution that was poured into the flow system. Hydrostatic pressure of 10〜30 cmH_2O was applied to enable the blood flow smoothly through the channels. Local area images of the blood cells were observed under intra-vital microscope, recorded using a high-speed video camera and analyzed by an image processor of PC base. AFM was used in contact mode that gives the relation between deflection and displacement of the AFM cantilever. The spring constant and Young's modulus of erythrocyte was estimated by applying the Hooke's law and the Hertz model respectively on the data of force curve. As the result, deformability of diabetic erythrocytewas significantly lower than that of healthy controls, especially at higher shear rate. The spring constant and Young's modulus of diabetic erythrocytes were much higher than those of healthy controls. These erythrocytes were obviously stiffened to be hard to deform in the capillary flow passage that may follow to the growth of microangiopathy. Diabetic platelets showed the augmented inclination of their adhesion, aggregation and more acceleration of the thrombus formation. This suggested that the endothelial cell layer of micro blood vessel might be easy to be Injured and lead the platelets to form thrombus shortly.