Single-cell measurement of red blood cell oxygen affinity

TL;DR

This study introduces a high-throughput system for measuring oxygen saturation, cell volume, and hemoglobin concentration in individual red blood cells, revealing variability in oxygen affinity linked to hemoglobin concentration.

Contribution

The paper presents a novel method for single-cell measurement of oxygen affinity, providing insights into cellular variability and its determinants in blood cells.

Findings

Peak variability at 2.5% oxygen partial pressure

Oxygen affinity correlates with hemoglobin concentration

Independence from osmolarity suggests variation in hemoglobin to DPG ratio

Abstract

Oxygen is transported throughout the body by hemoglobin in red blood cells. While the oxygen affinity of blood is well understood and is routinely assessed in patients by pulse oximetry, variability at the single-cell level has not been previously measured. In contrast, single-cell measurements of red blood cell volume and hemoglobin concentration are taken millions of times per day by clinical hematology analyzers and are important factors in determining the health of the hematologic system. To better understand the variability and determinants of oxygen affinity on a cellular level, we have developed a system that quantifies the oxygen saturation, cell volume and hemoglobin concentration for individual red blood cells in high-throughput. We find that the variability in single-cell saturation peaks at an oxygen partial pressure of 2.5%, which corresponds to the maximum slope of the oxygen-hemoglobin dissociation curve. In addition, single-cell oxygen affinity is positively correlated with hemoglobin concentration, but independent of osmolarity, which suggests variation in the hemoglobin to 2-3 DPG ratio on a cellular level. By quantifying the functional behavior of a cellular population, our system adds a new dimension to blood cell analysis and other measurements of single-cell variability.