The stabilization of hemoglobin multiple emulsion for use as a red blood cell substitute

Abstract

Utilizing emerging multiple emulsion and liquid membrane technology to form stable hemoglobin-in-oil-in-water (Hb/O/W) multiple emulsion (ME) droplets, efforts were aimed at formulating an artificial red blood cell for use as a blood substitute or organ perfusion system, which provides adequate oxygen-carrying capacity. With the development of this methodology, using large-scale fabrication methods, a concentrated Hb solution (to 35 g/100 ml) was emulsified in oil to form microdroplets by using an appropriate nontoxic surfactant in the oil phase, followed by dispersion of the primary emulsion into an outer aqueous phase containing surfactant to form the ME. Of the various oils tested both white (mineral) and tricaproin (triglyceride) showed the highest encapsulation efficiency for hemoglobin. Surfactants were used in the liquid membrane and outer aqueous phases to form and stabilize the multiple emulsion droplets (artificial cells). The Hb encapsulation efficiency and the oxygen content of freshly prepared multiple emulsion were as much as 98% and 14 ml/100 ml ME, respectively. The average diameter of the prepared ME droplets was about 2 to 3 μm. The steady shear viscosity of the ME was similar to that of whole blood over the shear rate range studied. Sensitivity to shear was evaluated for shear rates to 2160 s −1 and showed only very small leakage of Hb from the ME droplets into the outer aqueous phase; also the stability of the “artificial cells” during short-term storage (i.e., less than 30 days)