Laser-optic techniques for assessing blood microrheology in health and disease

Blood microrheology and microcirculation is a vast field of research focusing on the properties of blood passing through lesser vessels and capillaries. In this part of the circulatory system, red blood cells (RBCs) determine the parameters of the flow, which impact the efficiency of oxygen transport and tissue supply. Various pathologies, such as cardiovascular diseases, diabetes mellitus, malaria and sickle cell disease alter parameters of RBCs severely impairing microcirculation. RBC abilities of reversible aggregation and deformation are among the main cellular properties ruling the hemorheology and microcirculation. In this review, we discuss five methods for blood microrheology and microcirculation in vitro studies: optical tweezers, flow chamber-coupled microscopy, laser aggregometry, laser diffractometry (ektacytometry) and flow cytometry. These techniques allow for assessing valuable cellular properties without significant damage to the cells during measurements. Some of the methods are used for studies on the scale of single cells, while others provide summarized parameters of thousands of cells. The possibilities of these techniques to study RBC aggregation and deformability are considered along with recent advances and current limitations.