DNA-containing interpolyelectrolyte complexes: interaction with liposomes
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Formation of complexes of DNA with cetylpyridinium bromide and polycations [viz., poly-N-ethyl-4-vinylpyridinium bromide and N-ethyl-4-vinylpyridinium and N-cetyl-4-vinylpyridinium bromides random copolymer (PVPEC)] and interaction of such complexes with negatively charged liposomes were studied. The dissociation constants of all the DNA-cation complexes are extremely low, and all the molecules are incorporated into the complexes. The complexes are large aggregates in which the number of molecules of cetylpyridinium bromide (or polycation monomer units) approximately is equal to that of the monomer units of DNA (ratio f1). Ether an increase or a decrease in the cation content produce a drastic decrease in the size of the particles of the complex. Complexes of DNA with cetylpyridinium bromide (f=0.1) dissociate completely after the addition of liposomes, as surfactant molecules fit into the lipid bilayer and the DNA chains are released into solution. In contrast, complexes of DNA with poly-N-ethyl-4-vinylpyridinium bromide (f=0.1) exhibit no interaction with liposomes. After the insertion of cetyl substituents into the polycation chain, DNA molecules are conveyed to the liposome surface: PVPEC/DNA complexes bind with liposomes without their dissociation to form ternary DNA-liposomes-PVPEC complex.