In vivo survival of selected murine carrier red blood cells after separation by density gradients or aqueous polymer two-phase systems

In order to explore possibilities of using erythrocytes as carrier systems for delivery of pharmacological agents, we have studied the ill vivo surviv al of murine carrier red blood cell populations enriched in young or old ce lls. Hypotonic-isotonic dialysis has been used to modify the cells as carri er systems and Percoll/albumin density gradients or counter-current distrib ution in aqueous polymer two-phase systems to separate them according to ag e. Hypotonic-isotonic dialysis produces a decrease in the red blood cell po pulations in vivo survival rate (from 9.5 to 7.8 days). Among the cells mod ified as carriers, the enriched young red blood cell populations show a hig her in vivo survival (half-life 6.5-7.4 days) than populations made up of p redominantly old red blood cells (half-life 4.7-6.2 days). Half-life of you ng or old circulating red blood cells was approximately one day longer when these cells were separated by counter-current distribution rather than by Percoll density gradients. Based on these results, hypotonic-isotonic dialy sis of whole and enriched young or old red blood cell populations, with hig her or lower survival rates, can be considered as a useful tool for modific ation of these cells as carriers. The final outcome of such changes can be translated into better control of plasma drug delivery during therapy.