A simple method for preparing poly(ethylene glycol) surface conjugated liposome encapsulated hemoglobins: physico-chemical properties long-term storage stability and their reactions with O2 CO and NO

摘要

During the last few decades, liposome encapsulated hemoglobin (LEH) dispersions have been investigated for use as red blood cell (RBC) substitutes. However, the process for formulating LEHs is cumbersome and the composition of the lipid mixture is often complex. This work investigates a simple approach for formulating LEHs from a simple lipid mixture composed of the high phase transition lipid distearoylphosphatidylcholine (DSPC) and cholesterol. In order to improve the circulation half-life and colloidal state of LEHs, the surface of unmodified LEHs was conjugated with poly(ethylene glycol) (PEG-LEHs). The results of this work show that PEG-LEH dispersions exhibited average diameters ranging from 166–195 nm that were colloidally stable for 4–5 months, hemoglobin (Hb) concentrations ranging from 9.6–14 g/dL, methemoglobin levels less than 1%, oxygen affinities (i.e. P50s) ranging from 20–23 mm Hg and cooperativity coefficients ranging from 1.4–2.2.The reactions of PEG-LEHs with physiologically important ligands, such as oxygen (O2), carbon monoxide (CO) and nitric oxide (NO), were also measured. It was observed that PEG-LEHs and RBCs exhibited retarded gaseous ligand binding/release kinetics compared to acellular Hbs. This result provides important insight into the pivotal role that the intracellular diffusion barrier plays in the transport of gases into and out of these structures. Collectively, our results demonstrate that the PEG-LEH dispersions prepared in this study show good potential as a RBC substitute.