Erythrocytes as carriers for recombinant human erythropoietin

The aim of this work was to encapsulate recombinant human erythropoietin (rHuEpo) in human and mouse red blood cells (RBCs) to improve the stability of encapsulated rHuEpo. The encapsulation of rHuEpo was achieved by an hypotonic dialysis-isotonic resealing procedure. A radioimmunoassay method was used for the estimation of rHuEpo. The hypoosmotic resistance of carrier erytrhocytes was studied by osmotic fragility measurements. Cell morphology was observed under scanning electron microscopy. Encapsulated rHuEpo was identified by an immunogold labeling assay. Encapsulation yields were 22% for human RBCs and 14% for mouse RBCs. Cell recovery was around 70%. Carrier-RBCs exhibited a tendency to spherocytic morphology, and showed the typical higher hypoosmotic resistance than normal RBCs. The presence of rHuEpo inside carrier RBCs was identified. The stability of encapsulated rHuEpo seems to be related to the experimental conditions used during the encapsulation procedure. An increase with time of released rHuEpo was observed in carrier-RBC suspensions. The encapsulation of rHuEpo in RBCs has been achieved for the first time. These carrier RBC-preparations may serve as an alternative sustained cell delivery system for the in vivo administration of rHuEpo.