Oxygen Carrier Based on Hemoglobin/Poly(l-lysine)-block-poly(l-phenylalanine) Vesicles

An oxygen carrier was prepared by encapsulating carbonylated hemoglobin (CO-Hb) molecules into polypeptide vesicles made from poly(L-lysine)-block-poly(L-phenylalanine) (PLL-b-PPA) diblock copolymers in aqueous medium at pH 5.8. The encapsulation was confirmed by confocal laser scanning microscopy (CLSM). The morphology and size of the vesicles were studied by field-emission scanning electron microscopy (ESEM). They had a spherical shape with a mean diameter of about 4 to 5 microm. The encapsulation efficiency of hemoglobin was 40 wt %, and the hemoglobin content in the vesicles was 32 wt %. The CO-Hb encapsulated in the PLL-b-PPA vesicles was more stable than free CO-Hb under ambient conditions. In the presence of a O(2) atmosphere, the CO-Hb in the vesicle could be converted into oxygen-binding hemoglobin (O(2)-Hb) under irradiation of visible light for 2 h. Therefore, the CO-Hb/PLL-b-PPA vesicles are expected to be used as red blood cell substitutes.