(23d) Hemoglobin Nanoparticles Made By Desolvation Precipitation May Function As a Therapeutic Artificial Oxygen Carrier

Purpose/Introduction: Blood transfusion is a lifesaving treatment for hypoxia, when organs and tissues are starved of oxygen. Unfortunately, blood cannot be available in all situations, including pre-hospital, battlefield, and remote care settings. Despite substantial research, no red blood cell substitute has ever been approved for clinical use. This work describes a new type of oxygen carrier based on the combination of hemoglobin (Hb), the oxygen carrying component of blood, and nanoparticle technology originally designed for drug delivery.

Experimental Design/Method: Hemoglobin nanoparticles (Hb-NPs) were formed by the desolvation process resulting in a suspension of uniform particles with no blood type limitations. During desolvation, ethanol, in which Hb is poorly soluble, is steadily added to a Hb solution resulting in effective supersaturation. At a critical saturation, precipitation into nanoparticles occurs, and a protein cross-linker is added to stabilize their size and shape. Finally, tangential flow filtration is used to rapidly exchange the final Hb-NPs into a physiological buffer solution. These Hb-NPs were characterized using traditional methods such as DLS, as well as more advanced assays for Hb activity and oxygen carrying potential.

Major Findings/Results: Hb-NPs made by this process had a mean diameter of 245 nm, similar in size to liposomes and other particles approved for intravenous use. Oxygen release kinetics revealed a dissociation constant of similar order of magnitude to that of a red blood cell. The oxygen binding equilibria of Hb-NPs showed high affinity and reversible binding and release of oxygen.

Summary of your interpretation of the data or conclusion: These findings suggest that Hb-NPs can be readily synthesized with a high Hb content and uniform size. They retain the oxygen carrying properties of the Hb protein, mimicking the red blood cell without constraints such as blood type or strict storage requirements. The uniform size and shape of Hb-NPs may overcome some barriers facing traditional oxygen therapeutics such as polymerized Hb products.