Аннотация:Nanodiamonds (ND) are characterized by notable biocompatibility and possibilities of surface conjugation. This is why they recently attracted high attention in regard to their potential applications in biology and medicine, especially, for bioimaging and drug delivery. Remarkable fluorescence and Raman spectroscopic properties make ND an efficient biomarker for tracking the interactions of specific molecules with biological systems. Implementing ND presumes their administration into the organism, in particular, by injecting them intravenously into the blood circulation. In this paper, we present our results in studying the effects of ND on blood fluidity via interaction with different blood constituents. Using different optical techniques (optical and fluorescence microscopy, Raman microspectroscopy, laser diffractometry, diffuse light scattering, etc.) we studied the interaction of ND of different sizes with blood plasma proteins and blood cells with special focus on red blood cells (RBC) in in-vitro and in-vivo conditions. We showed that ND do interact with RBC membrane in a concentration dependent manner. This interaction may, in certain conditions, influence the membrane structure and affect the RBC mechanical and microrheological properties, deformability and aggregation, which are the determinants of blood rheology and microcirculation. The obtained results imply that controlling the blood microrheologic properties is a necessary prerequisite for the optimization of ND application protocols.