The buckling instability of aggregating red blood cells

Abstract

Plasma proteins such as fibrinogen induce the aggregation of red blood cells (RBC) into rouleaux, which are responsible for the pronounced shear thinning behavior of blood, control the erythrocyte sedimentation rate (ESR) – a common hematological test – and are involved in many situations of physiological relevance such as structuration of blood in the microcirculation or clot formation in pathological situations. Confocal microscopy is used to characterize the shape of RBCs within rouleaux at equilibrium as a function of macromolecular concentration, revealing the diversity of contact zone morphology. Three different configurations that have only been partly predicted before are identified, namely parachute, male-female and sigmoid shapes, and quantitatively recovered by numerical simulations. A detailed experimental and theoretical analysis of clusters of two cells shows that the deformation increases nonlinearly with the interaction energy. Models indicate a forward bifurcation in which the contacting membrane undergoes a buckling instability from a flat to a deformed contact zone at a critical value of the interaction energy. These results are not only relevant for the understanding of the morphology and stability of RBC aggregates, but also for a whole class of interacting soft deformable objects such as vesicles, capsules or cells in tissues.

Hydrodynamics and rheology of a vesicle doublet suspension

“…For weak to moderate adhesion strength, vesicle membranes are flattened in the contact region while the rest of vesicle maintains a nearly spherical shape [40][41][42]60]. Under a strong adhesion, however, the vesicle membranes in the contact region buckle and form a sigmoidal shape that has also been observed in RBC doublets [29,30,33]. An external electric field is also able to buckle a vesicle membrane that is adhered to a solid substrate [54].…”

“…Alternatively, researchers have used the micropipette to measure the adhesive force between two vesicles bound by strong adhesion [40,62]: Evans and Metcalfe [40] were able to measure the reduction in the free energy per unit area of membrane-membrane contact formation due to the van der Waals' attraction. For the adhesive interaction between two lipid bilayer membranes in buffer solutions, a typical range for the energy density is between 1 to 10 µJ/m 2 , similar to the adhesion energy density of 3 µJ/m 2 between two RBCs [33]. Frostad et al [62] investigated the depletion-attraction induced adhesion between two vesicles, and identified the dynamic role of membrane tension during membrane adhesion/peeling.…”

“…Using the Lennard-Jones (L.-J.) potential for point-point interaction between two vesicle membranes without the molecular details of adhesive interactions between RBCs, Flormann et al [33] found that, under strong adhesion, the membrane may buckle to a sigmoidal shape in the contact region. Such a sigmoidal vesicle shape is also observed in RBC doublets and explained in a slightly different model [30].…”

“…However, adhesive interactions between RBCs lead to RBC clusters that are expected to alter the rheological properties of the RBC suspension [31,39]. Hydrodynamic simulations of adhesive vesicles in a quiescent flow have revealed physical insights to the equilibrium shapes of RBC aggregates in both experiments [33] and theory [30]. The main goal of this work is to investigate the hydrodynamics of adhesive vesicles in flow conditions common in microfluidics such as a planar shear flow and an extensional flow.…”

Hybrid Erythrocyte Liposomes: Functionalized Red Blood Cell Membranes for Molecule Encapsulation

“…The interior of the liposomes lights up in green under the microscope indicating that the dextran is located within the hybrid liposomes. Dextran has been previously reported to interact with the RBC membrane at larger concentration of dextran (>10 mg mL −1 ) 24–26. The homogeneous color and intensity of the liposomes, however, indicate that the molecules are homogenously distributed within the liposomes (within the resolution limit of the microscope).…”