ERYTHROCYTES AS CARRIERS FOR RECOMBINANT-HUMAN-ERYTHROPOIETIN

Purpose. The aim of this work was to encapsulate recombinant human ery thropoietin (rHuEpo) in human and mouse red blood cells (RBCs) to impr ove the stability of encapsulated rHuEpo. Methods. The encapsulation o f rHuEpo was achieved by an hypotonic dialysis-isotonic resealing proc edure. A radioimmunoassay method was used for the estimation of rHuEpo . The hypoosmotic resistance of carrier erytrhocytes was studied by os motic fragility measurements. Cell morphology was observed under scann ing electron microscopy. Encapsulated rHuEpo was identified by an immu nogold labeling assay. Results. Encapsulation yields were 22% for huma n RBCs and 14% for mouse RBCs. Cell recovery was around 70%. Carrier-R BCs exhibited a tendency to spherocytic morphology, and showed the typ ical higher hypoosmotic resistance than normal RBCs. The presence of r HuEpo inside carrier RBCs was identified. The stability of encapsulate d rHuEpo seems to be related to the experimental conditions used durin g the encapsulation procedure. An increase with time of released rHuEp o was observed in carrier-RBC suspensions. Conclusions. The encapsulat ion of rHuEpo in RBCs has been achieved for the first time. These carr ier RBC-preparations may serve as an alternative sustained cell delive ry system for the in vivo administration of rHuEpo.