Drag-reducing polymers (DRPs) are nontoxic water-soluble blood additives that have been shown to beneficially alter hemodynamics when delivered intravenously in nanomolar concentrations. This study examines the ability of DRPs to alter the traffic of mixtures of normal and less-deformable red blood cells (RBCs) through branched microchannels and is intended to support and expand upon previous experiments within straight capillary tubes to promote DRPs for future clinical use. Branched polydimethylsiloxane microchannels were perfused with a mixture of normal bovine RBCs also containing heat-treated less-deformable RBCs at a hematocrit of 30% with 10 ppm of the DRP poly(ethylene oxide) (MW 4M Da). Suspensions were driven by syringe pump, collected at outlets, and RBC dimensions measured while subject to shear stress to determine the proportion of healthy RBCs in each sample. DRPs eliminated evidence of the plasma skimming phenomena and significantly increased the pressure drop across microchannels. Further, DRPs were found to cause an increase in the proportion of healthy RBCs exiting the branch outlet from -8.5 ± 2.5% (control groups) to +12.1 ± 5.4% (n = 6, p = 0.02). These results suggest DRP additives may be used to improve the perfusion of less-deformable RBCs in vivo and indicates their potential for future clinical use.
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