Structure and Solution Properties of Lipidheme-Microsphere

Abstract

Triglyceride microsphere emulsified with phospholipid derivative of heme (5, 10, 15, 20-tetrakis[α,α,α,α-o-[2,2-dimethyl-20-[2-(trimethylammonioethoxy) phosphonatoxy]eicosanamido]phenyl]porphinatoiron(II); lipidheme) provides a totally synthetic artificial red cell (lipidheme-microsphere; LH-M). Its structure, solution properties and O₂ binding ability are described. The particle diameter of the LH-M was ca. 90 nmϕ elucidated by electron microscopy. Viscosity of the LH-M suspension (∼1.5 cP) was much lower than that of human blood and the viscosity of mixed system of LH-M/human blood (1/1(v/v)) was 2.5 cP. Specific gravity, osmotic pressure, and colloid osmotic pressure of the LH-M suspension also satisfied the physiological needs. The LH-M can bind O₂ reversibly in response to O₂ pressure (P₅₀(O₂): 41 torr (pH 7.4, 37°C)). O₂ solubility of the LH-M was more than that of human blood caused by its high heme concentration.