SPECIFIC TARGETING WITH POLY(ETHYLENE GLYCOL)-MODIFIED LIPOSOMES - COUPLING OF HOMING DEVICES TO THE ENDS OF THE POLYMERIC CHAINS COMBINES EFFECTIVE TARGET BINDING WITH LONG CIRCULATION TIMES
G. Blume et al., SPECIFIC TARGETING WITH POLY(ETHYLENE GLYCOL)-MODIFIED LIPOSOMES - COUPLING OF HOMING DEVICES TO THE ENDS OF THE POLYMERIC CHAINS COMBINES EFFECTIVE TARGET BINDING WITH LONG CIRCULATION TIMES, Biochimica et biophysica acta, 1149(1), 1993, pp. 180-184
One possibility for bringing drugs to their specific targets is to use
the drug-laden liposomes that have been made target- specific by the
attachment of appropriate proteins. Such 'directed' proteoliposomes an
d most other particles are rapidly removed from the bloodstream, howev
er, by the mononuclear phagocytes in the liver and spleen. This causes
suboptimal drug accumulation at the target site. Coating the liposome
surface with poly(ethylene glycol) (PEG) may prolong the circulation
time of liposomes. Using plasminogen as a homing device we have shown
that the PEG-modified liposomes with such a homing device coupled to t
he ends of the long PEG chains may combine long vesicle circulation ti
mes in the blood with high target binding capability. The PEG-coated p
roteoliposomes with homing devices attached at the very bilayer surfac
e, on the contrary, are longlived but have only little or no capabilit
y to bind to their targets.