Influence of interaction time on the red blood cell (dis)aggregation dynamics in vitro studied by optical tweezers

Optical tweezers (OT) is a unique Nobel Prize winning technology that has been widely used in studying cell interaction dynamics at a single-cell level with highly accurate manipulating of living cells and the ability to detect ultra-low intercellular forces. The reversible aggregation process of red blood cells (RBCs) that strongly influences the blood rheological properties thus being critical for blood microcirculation has long been research studied. However, in spite of plentiful researches dealing with RBC aggregation behavior based on an average response of a large number of cells, the detailed mechanism and the applicability of the two coexistent yet mutually opposed models to this reversible process require additional information. In this study, a two-channel optical tweezers system is utilized to reveal the influence of the cell interaction time (0-300 sec) on the RBC (dis)aggregation dynamics. The results show that for RBC enforced disaggregation in autologous plasma, the longer the two RBCs adhere to each other, the stronger the intercellular interaction is, and the lower the degree that a certain optical pulling force can separate two cells, whereas no significant effect of cell interaction time on RBC aggregation process was observed. This observation indicates that the RBC aggregation and disaggregation in autologous plasma are governed by different mechanisms and that the hysteresis effect, namely the dependence of the disaggregation force on RBC interaction history, is a significant feature that needs special consideration in researches related to the RBC disaggregation process.