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

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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.