A biomimetic microfluidic chip to study the circulation and mechanical retention of red blood cells in the spleen

Abstract

Red blood cells (RBCs) are deformable and flow through vessels narrower than their own size. Their deformability is most stringently challenged when they cross micrometer-wide slits in the spleen. In several inherited or acquired RBC disorders, blockade of small vessels by stiff RBCs can trigger organ damage, but a functional spleen is expected to clear these abnormal RBCs from the circulation before they induce such complications. We analyzed flow behavior of RBCs in a microfluidic chip that replicates the mechanical constraints imposed on RBCs as they cross the human spleen. Polymer microchannels obtained by soft lithography with a hydraulic diameter of 25 lm drove flow into mechanical filtering units where RBCs flew either slowly through 5-to 2-lm-wide slits or rapidly along 10-lm-wide channels, these parallel paths mimicking the splenic microcirculation. Stiff heated RBCs accumulated in narrow slits seven times more frequently than normal RBCs infused simultaneously. Stage-dependent retention of Plasmodium falciparuminfected RBCs was also observed in these slits. We also analyzed RBCs from patients with hereditary spherocytosis and observed retention for those having the most altered mechanical properties as determined by ektacytometry. Thus, in keeping with previous observations in vivo and ex vivo, the chip successfully discriminated poorly deformable RBCs based on their distinct mechanical properties and on the intensity of the cell alteration. Applications to the exploration of the pathogenesis of malaria, hereditary spherocytosis, sickle cell disease and other RBC disorders are envisioned.

Splenic Retention of Plasmodium falciparum Gametocytes To Block the Transmission of Malaria

“…Mature gametocytes from 2 different laboratory strains and a sample directly collected from the blood of a P. falciparum-infected patient were exposed to calyculin at 50 nM for 2 h and then infused through microfluidic chips. This method has been shown to recapitulate the mechanical constraints imposed on RBC as they cross interendothelial slits in the human spleen and has been validated with an array of poorly deformable RBC (32). Exposure to calyculin induced a marked enrichment to 72.40% Ϯ 13.64% in mature gametocytes in the narrowest slits of the chips versus 27.60% Ϯ 13.64% for the DMSO-exposed gametocytes (Fig.…”

“…The microfluidic biochips were cast in polydimethylsiloxane (PDMS; Sylgard, France), a silicone elastomer produced as described previously (32). Each biochip comprised 8 parallel filtering units connected to infusion tubing.…”

Monitoring Biological Cell Flow within a Mimicking Capillary Device with Impedance Measurement

“…The blood flow and the mechanical constraints imposed on RBC as they crossed microcapillaries with hydraulic diameter down to 5 μm can be obtained ( Figure 1B). A SU8 mold is used with PDMS molding step to obtain the microfluidic chip [4]. This mold has two different thicknesses corresponding to two steps of mold fabrication: the first step use a spin coating of is a thin 5 μm SU8 layer for the restriction channel associated to a UV photolithography process.…”

Automatic counting method for complex overlapping erythrocytes based on seed prediction in microscopic imaging

“…1 Mature RBCs are nonnucleated, biconcave disc-shaped cells of 7-8 m in diameter, 2 m-thick with an average volume of 80-100 m 3 . 2 RBC counting is one of the most commonly performed medical tests as it plays a vital role in the diagnosis of various diseases.…”