Applying methods of diffuse light scattering and optical trapping for assessing blood rheological parameters: erythrocytes aggregation in diabetes mellitus

Background and Objectives: Aggregation parameters of blood characterize red blood cells interaction processes which play a major role in the microcirculation regulation. It was shown that these parameters are significantly different in case of Diabetes Mellitus (DM) and therefore can be proposed as a novel parameter of the disease state and therapy efficiency. Usage of diffuse methods of measuring aggregation properties in whole blood combined with the single cell level measuring technique will allow creating a new complete approach to investigate the hemorheological state of the blood in various socially important disease. Materials and Methods: For assessing the time of spontaneous aggregation, hydrodynamic strength, aggregation index and deformability properties of ensemble of RBCs in whole blood we used commercially available aggregometer Rheoscan-AnD300 (Rheomeditech, Korea). Operation of this device is based on measuring the intensity of laser light scattered by whole blood samples. Measurements of RBC aggregating/disaggregating forces were performed using home-made 2-channelled optical tweezer (OT) in high-diluted autologous plasma. Two cells were manipulated and brought to the 40% of cell surface contact forming an aggregate. The minimal trapping force required to prevent the complete aggregation (aggregating force F$_A$) was measured. The minimal trapping force required to disassemble the aggregate completely (disaggregating force F$_D$) was also measured. Results: The measurements of RBC interaction forces were performed in groups of healthy donors and patients suffering from DM. The measured value of the aggregation force in DM was F$_A$ = 4.2 $\pm$ 1.2 pN which 1.5 times exceeds the aggregating force in norm (F$_A$ = 2.7 $\pm$ 1.5 pN) while the disaggregating forces F$_D$ were found to be nearly the same. DM is characterized by enhanced aggregation. It was shown that the characteristic time of aggregates formation is reduced in whole blood of patients with DM relative to the control group. Conclusions: The statistically significant difference in aggregating forces in norm and DM allowed to propose a novel aggregating parameter R = F$_D$ / F$_A$ which can diagnose the microrheological state of the pathological blood in case of DM. Information about alterations of the time of aggregates formation can be considered as an indication of DM as well as for monitoring the patients treatment efficiency.