Influence of Pulsed He–Ne Laser Irradiation on the Red Blood Cell Interaction Studied by Optical Tweezers

Abstract

Optical Tweezers (OT), as a revolutionary innovation in laser physics, has been extremely useful in studying cell interaction dynamics at a single-cell level. The reversible aggregation process of red blood cells (RBCs) has an important influence on blood rheological properties, but the underlying mechanism has not been fully understood. The regulating effects of low-level laser irradiation on blood rheological properties have been reported. However, the influence of pulsed laser irradiation, and the origin of laser irradiation effects on the interaction between RBCs remain unclear. In this study, RBC interaction was assessed in detail with OT. The effects of both continuous and pulsed low-level He–Ne laser irradiation on RBC aggregation was investigated within a short irradiation period (up to 300 s). The results indicate stronger intercellular interaction between RBCs in the enforced disaggregation process, and both the cell contact time and the initial contact area between two RBCs showed an impact on the measured disaggregation force. Meanwhile, the RBC aggregation force that was independent to measurement conditions decreased after a short time of pulsed He–Ne laser irradiation. These results provide new insights into the understanding of the RBC interaction mechanism and laser irradiation effects on blood properties.

Optical Tweezers in Studies of Red Blood Cells

“…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.…”

“…The experimental samples used for general RBC measurements with OTs are erythrocytes suspensions with controlled concentrations. Normal circulating human RBCs can be obtained by washing the fingertip-prick blood drops in phosphate buffer saline [102] and for evaluation of the maturing RBCs during different development stages in erythropoiesis; the immature RBCs can be obtained by aspirating bone marrow cells from the iliac crest [103]. The cells are suspended in designed solutions for different measurement purposes, such as plasma or model solutions containing different types and concentrations of fibrous biomolecules, neutral polymers or nanoparticles.…”

“…On the other hand, the "cross-bridging" model indicates that two adjacent RBCs are connected by the "bridges" formed by the macromolecules attached to the membrane of both cells, thus the strength of the interaction is associated with both the type and concentration of macromolecules in the surrounding environment [145]. In OTs-based RBC interaction measurements, the aggregation force is measured as the minimum trapping force to stop RBCs from clumping as illustrated in Figure 10a, and the disaggregation force is measured as the optical pulling force applied to break RBC bonds and decrease the contact area between the two cells as shown in Figure 10b [102]. In the prototypical procedure of RBC aggregation force measurement, linear RBC aggregate consisting of two or several cells is held and slightly stretched from two opposite end-points, and the trapping strength is slowly decreased while the interaction area remains constant.…”

“…Figure 10. Illustration of measurements of RBC mutual interaction forces in RBC aggregates containing two cells [102]. (a) The aggregate is slightly stretched by two opposite end-points and the RBC aggregation force is measured by slowly decreasing the trapping strength until the optical force matches with the intercellular force and the cells escape from the traps.…”

Editorial for the Special Issue on Optical Trapping and Manipulation: From Fundamentals to Applications

“…Two papers are concerned with the investigation of mechanical interactions of red blood cells (RBCs). Zhu et al have investigated the disaggregation of RBCs by using optical tweezers to quantify the force required to separate aggregated cells, showing that a short irradiation from a pulsed helium-neon laser may reduce the aggregation force [1]. Avsievich et al report on the effect of polymeric nanocapsules-a model for drug delivery vehicles-on the aggregation force of RBCs, finding no change and no cytotoxicity as a result of the nanocapsule treatment [2].…”