Assessment of transient changes in oxygen diffusion of single red blood cells using a microfluidic analytical platform

Red blood cells (RBCs) capability to deliver oxygen (O 2 ) has been routinely measured by P50. Although this defines the ability of RBCs to carry O 2 under equilibrium states, it cannot determine the efficacy of O 2 delivery in dynamic blood flow. Here, we developed a microfluidic analytical platform (MAP) that isolates single RBCs for assessing transient changes in their O 2 release rate. We found that in vivo (biological) and in vitro (blood storage) aging of RBC could lead to an increase in the O 2 release rate, despite a decrease in P50. Rejuvenation of stored RBCs (Day 42), though increased the P50, failed to restore the O 2 release rate to basal level (Day 0). The temporal dimension provided at the single-cell level by MAP could shed new insights into the dynamics of O 2 delivery in both physiological and pathological conditions.