Microfluidic biosensor for monitoring temporal variations of hemorheological and hemodynamic properties using an extracorporeal rat bypass loop.

In this study, we propose a novel microfluidic biosensor for monitoring hemorheological and hemodynamic properties using an extracorporeal rat bypass loop. To monitor temporal variations of biophysical properties including viscosity, flow rate, and pressure of rat blood, a complex fluidic network is established by connecting the abdominal aorta and jugular vein to an extracorporeal bypass loop including a flow stabilizer and a microfluidic biosensor. Three biophysical properties are simultaneously measured through label-free operation and sensorless detection based on two sequential flow controls in the microfluidic channel. A discrete fluidic-circuit model is employed to derive analytical formulas for the complex fluidic network. First, to evaluate the measurement accuracy of the proposed method, a peristaltic pump is used as substitute for a rat. The flow rate and viscosity of 20% glycerin (test fluid) circulating within the fluidic network are measured, and then the results are compared with those obtained using conventional methods. The normal differences between two measurement methods are less than 4%. Then, the proposed method is used to monitor temporal variations in biophysical properties of blood circulating within the complex fluidic network under normal and continuous hemodilution conditions. Rats require at least 30 min to adapt to different fluidic environments. The flow rate, pressure, and hematocrit of rat blood tend to decrease gradually because of continuous hemodilution effect. Furthermore, the reduced flow rate increases blood viscosity under hemodilution condition. These experiments demonstrate that the proposed method can effectively monitor temporal variations of biophysical properties of rat blood under ex vivo conditions.