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

Abstract

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.

Optical Tweezers in Studies of Red Blood Cells

“…In studies of the characteristics of blood components and rheology at a single-cell level, the easy-to-implement and well-developed conventional dual-beam OTs are the most commonly used trapping geometry. In a typical dual-beam OTs system as shown in Figure 4 [73], by using polarizing beam splitters (PBS), one infrared laser beam is split into two polarization-based beams and focused by a large numerical aperture microscope objective. With beam positions being adjustable by rotating reflective mirrors or by moving the sample stage, two individual RBCs can be trapped and controlled simultaneously.…”

“…With the double-beam OTs system as illustrated in Figure 4 and the above-stated methods, our group recently revealed the influence of cell interaction time (up to 300 s) on RBC disaggregation dynamics [73,102]. The results showed that the RBC disaggregation force increases with initial interaction time between two RBCs, whereas the aggregation force is independent to the cell contact time.…”

“…. Schematic diagram of a typical two-channel optical tweezers system used for RBCs studies [73]. Two trapping channels are formed by focusing two light beams divided by polarizing states from a single laser source through a large numerical aperture objective.…”

“…With a given trapping power, the velocity of the flow can be slowly increased until the viscous dragging force matches the trapping strength and causes the particle to escape from the trap. The trapping force proportional to the trapping power can then be estimated by the dragging force at the escaping velocity [73].…”

“…Currently, single-cell level methods, such as micropipette aspiration technique (MAT), scanning electron microscopy (SEM) and atomic force microscopy (AFM), have been applied to RBC studies and have contributed a lot to the current understanding of the special characteristics of RBCs and blood rheology [95]. To date, many aspects of RBCs, including membrane elasticity [96], disaggregation dynamics [73], shape and electrical charge of the membrane surface [97], as well as the special characteristics under different physiological and pathological conditions [98][99][100][101] have been investigated with various OTs systems. The main research methods and results in RBC studies achieved by OTs are reviewed to provide inspiration for novel experimental design of OTs measurement systems and to spur potential new applications of OTs in blood studies.…”