3 years ago

High Aspect Ratio Sub-Micrometer Channels Using Wet Etching: Application to the Dynamics of Red Blood Cell Transiting through Biomimetic Splenic Slits

High Aspect Ratio Sub-Micrometer Channels Using Wet Etching: Application to the Dynamics of Red Blood Cell Transiting through Biomimetic Splenic Slits
Priya Gambhire, Emmanuèle Helfer, Cécile Iss, Scott Atwell, Catherine Badens, Igor Ozerov, Frédéric Bedu, Anne Charrier, Annie Viallat
Nanoparticles delivering drugs, disseminating cancer cells, and red blood cells (RBCs) during splenic filtration must deform and pass through the sub-micrometer and high aspect ratio interstices between the endothelial cells lining blood vessels. The dynamics of passage of particles/cells through these slit-like interstices remain poorly understood because the in vitro reproduction of slits with physiological dimensions in devices compatible with optical microscopy observations requires expensive technologies. Here, novel microfluidic PDMS devices containing high aspect ratio slits with sub-micrometer width are molded on silicon masters using a simple, inexpensive, and highly flexible method combining standard UV lithography and anisotropic wet etching. These devices enabled revealing novel modes of deformations of healthy and diseased RBCs squeezing through splenic-like slits (0.6–2 × 5–10 × 1.6–11 µm3) under physiological interstitial pressures. At the slit exit, the cytoskeleton of spherocytic RBCs seemed to be detached from the lipid membrane whereas RBCs from healthy donors and patients with sickle cell disease exhibited peculiar tips at their front. These tips disappeared much slower in patients' cells, allowing estimating a threefold increase in RBC cytoplasmic viscosity in sickle cell disease. Measurements of time and rate of RBC sequestration in the slits allowed quantifying the massive trapping of spherocytic RBCs. Microfluidic PDMS devices containing high aspect ratio slits with sub-micrometer width are used as biomimetic inter-endothelial spleen slits to study the mechanical properties of red blood cells (RBCs). New deformation shapes are observed with RBCs from patients with Sickle Cell Disease and Hereditary Spherocytosis (HS). For example, HS cells display possible membrane/cytoskeleton dissociation at the slit exit.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/smll.201700967

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