This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Blood is a complex biological fluid composed of deformable cells and platelets suspended in
plasma, a protein-rich liquid. The peculiar nature of blood needs to be considered when designing a drug
delivery strategy based on systemically administered carriers. Here, we report on an in vitro fluid dynamic
investigation of the influence of the microcapillary flow of red blood cells (RBCs) on micron sized carriers
by high speed imaging methods. The experiments were carried out in a 50μm diameter glass capillary that
mimicked the hydrodynamic conditions of human microcirculation. Spherical μ particles (μ-Ps), with sizes
ranging between 0.5 and 3μm, were tested. Images of the flowing RBCs and μ-Ps were acquired by a highspeed/ high-magnification microscopy. The transport and distribution of rigid particles in a suspension of
RBCs under shear flow were followed for: i) the migration of RBCs towards the vessel centerline due to
their deformability; ii) the cross-flow migration of μ-Ps towards the vessel wall due to their hydrodynamic
interactions with RBCs; iii) the radial distribution of μ-Ps in the presence of RBCs. This study suggests that
the therapeutic efficacy of μ-Ps could be ultimately affected by their interactions with the flowing RBCs in
the vasculature
