INSERTION OF POLY(ETHYLENE GLYCOL) DERIVATIZED PHOSPHOLIPID INTO PREFORMED LIPOSOMES RESULTS IN PROLONGED IN-VIVO CIRCULATION TIME

Transfer of MPEG(1900)-DSPE from micellar phase to pre-formed liposome s imparts long in vivo circulation half-life to an otherwise rapidly c leared lipid composition, MPEG(1900)-DSPE transfers efficiently and qu ickly in a time and temperature dependent manner, There is negligible content leakage and a strong correlation between assayed mol% MPEG(190 0)-DSPE, liposome diameter increase, and pharmacokinetic parameters su ch as distribution phase half-life, Since a biological attribute (lipo some clearance rate) can be modified by the insertion process, it sugg ests a simple and economical way to impart site-specific targeting to a variety of liposome delivery systems, This method is also a convenie nt way to measure the 'brush' thickness of such conjugates directly.