Assessment of Continuous Flow-Dependent Red Cell Aggregation Using a Microfluidic Chip

Measuring RBC aggregation can be considered as a valuable tool for detecting pathological diseases. Most previous methods need to stop and run blood flows periodically. Thus, it is impossible to probe RBC aggregation in continuously varying infusion flow. To resolve the issues, a novel bifurcated continuous-flow mechanism is suggested to probe RBC aggregation without periodic interruption of blood flow. A microfluidic chip is then designed to split single flow into two branches (low flow rate and high flow rate). RBC aggregation occurs in the low flow-rate channel, whereas it is dispersed fully in the high flow-rate channel. Using a syringe pump, blood is infused into a microfluidic chip at constant and sinusoidal pattern. RBC aggregation index (AI) is calculated from time-lapse imaging intensity within each channel. From fluidic circuit analysis and experimental results, the optimal infusion flow rate is determined as Qsp = 0.5~2 mL/h. The AI is higher at Hct = 30% than at Hct = 50%. The high concentration of dextran solution increases AI considerably. The period of pulsatile infusion flow rate has a strong influence on time-lapse AI. In conclusion, the present method can be capable of measuring time-lapse AI consistently, without interrupting infusion flow.