Extensional flow for assessing the effect of nanocarriers on the mechanical deformability of red blood cells

•We studied the effect of nanoparticles (NPs) on the mechanical behavior of red blood cells (RBCs) under an extensional flow in a microfluidic domain.•Compared the RBCs mechanical response in contact with magnetic and non-magnetic NPs.•RBCs deformability decreased when the cells got in contact with NPs, being that difference higher for magnetic NPs.•Opens new possibilities regarding applications of cell-nanoparticle interactions in targeted drug delivery systems. The effect of nanoparticles on the mechanical behavior of red blood cells (RBCs) under an extensional flow has not been extensively studied. In this work, by using a microfluidic hyperbolic contraction, it is assessed the deformability of healthy RBCs in contact with ∼20 nm nanoparticles of magnetic iron and non-magnetic cerium. The results showed that, under a controlled extensional flow, the healthy RBCs deformability index depended on the cells’ velocity along the microfluidic contraction. Additionally, the results showed that the deformability index of the RBCs decreased when the cells got in contact with the nanoparticles, being that difference higher for the magnetic nanoparticles and for the longer exposition times. The RBCs presented a logarithmic deformability index vs velocity trend, with variations according to the magnetic or non-magnetic properties of the nanoparticles, to the concentration and to the exposure time. Thus, the representation of the deformation index as a function of velocity seems to be a promising method to evaluate the mechanical behavior of the cells. Such knowledge will be essential for further understanding how the cell-nanoparticle interactions occur in RBCs disorders, and will open new possibilities regarding future applications of these nanocarriers in targeted drug delivery systems for therapeutics.