Amphiphilic polymers of N-vinylpyrrolidone, which contain fragments of water-soluble polymer and hydrophobic end groups and are able, to build into liposome coats were synthesized.
These polymers were obtained by two-phase method. Fist the radical polymerization of monomers (N-vinylpyrrolidone, acrylamide) in presence of initiator (dinitrile of azobisisobutyric acid) and functional chain transmitters (mercaptanes) was carried out.
Changing the mercaptane amount, yield and molecular weight of polymers xan be controlled. Polymers with different molecular weight (Mn=1500-14000) were synthesized. Coincidence of molecular weights obtained by titration and by ebullioscopy corroborates that these polymers have only one functional end group.
For introduction of a long chain aliphatic group the reaction between polymer with carboxylic end group and stearylamine in the presence of dicyclohexylcarbodiimide or reaction between polymer with amine end group and chloranhydride of stearic acid was carried out.
Obtained polymers were soluble in water and as it was shown form associates with the compounds, which contains hydrophobic fragments. Also polymers form micelles in water solutions. The influence of polymer molecular weight on critical concentration of aggregation was studied. Obtained modified liposomes were of 165-190 nm sizes.
Synthesized polymers protect liposomes from destroying effect of polycation. These studies were carried out by means of fluorescent marker and method of studying of modified-by-polymers liposomes fraught by pyren.
Behavior of modified by synthesized polymers of N-vinylpyrrolidone liposomes was studied on white linear mice. It was determined that introduction of polymers increases time of liposome circulation in blood and decreases liposome capture by liver.
V.P. Torchilin, M.I. Shtilman et al. // Biochim. Biophys. Acta. 1994. V.1195. P.181-184.