Changes in red blood cells biomechanical properties induced by albumin and fibrinogen membrane adsorption: A study using flow cytometry and optical tweezers

Despite its rheological significance, the mechanisms of red blood cells (RBC) spontaneous aggregation are not understood completely. One of the discussed models is the molecular bridging which is caused by the adsorption of proaggregant macromolecules onto RBC membrane. In this work, using laser optical techniques, we studied how adsorption of human serum albumin (HSA) and fibrinogen macromolecules onto the RBC membrane changed cellular biomechanical properties relatively to the RBC aggregation process. Flow cytometry results demonstrated that incubation of RBC in fibrinogen solution did not change values in either side (SSC) or front (FSC) scattering channel of the cytometer. Incubation of RBC in HSA solution showed that mean FSC and SSC values were slightly higher in comparison with intact RBC control. Meanwhile, RBC aggregation force (F_agg), measured by laser tweezers in autologous plasma, linearly increased with fibrinogen concentration and was almost independent of HSA content. We compared these data with the changes in light scattering intensity and aggregation forces of RBC incubated in glutaraldehyde solution. Results showed that SSC values significantly increased for RBC incubated in glutaraldehyde solution and F_agg of such cells was nearly absent. We hypothesized that serum albumin may influence the biomechanical properties of RBC due to non-specific adsorption leading to the alterations of membrane-bounded hemoglobin resulting in controversial effects on RBC aggregation.