DNA-CONTAINING INTERPOLYELECTROLYTE COMPL EXES - INTERACTION WITH LIPOSOMES

Formation of complexes of DNA with cetylpyridinium bromide and polycat ions [viz., poly-N-ethyl-4-vinylpyridinium bromide and N-ethyl-4-vinyl pyridinium and N-cetyl-4-vinylpyridinium bromides random copolymer (PV PEC)] and interaction of such complexes with negatively charged liposo mes were studied. The dissociation constants of all the DNA-cation com plexes 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 f al most-equal-to 1). Either an increase or a decrease in the cation conte nt produce a drastic decrease in the size of the particles of the comp lex. Complexes of DNA with cetylpyridinium bromide (f = 0.1) dissociat e completely after the addition of liposomes, as surfactant molecules fit into the lipid bilayer and the DNA chains are released into soluti on. In contrast, complexes of DNA with poly-N-ethyl-4-vinylpyridinium bromide (f = 0.1) exhibit no interaction with liposomes. After the ins ertion of cetyl substituents into the polycation chain, DNA molecules are conveyed to the liposome surface: PVPEC/DNA complexes bind with li posomes without their dissociation to form ternary DNA-liposomes-PVPEC complex.