Layer-by-layer deposition of oppositely charged polyelectrolytes on the surface of condensed DNA particles

DNA can be condensed with an excess of polycations in aqueous solutions for ming stable particles of submicron size with positive surface charge. This charge surplus can be used to deposit alternating layers of polyanions and polycations on the surface surrounding the core of condensed DNA, Using pol y-L-lysine (PLL) and succinylated PLL (SPLL) as polycation and polyanion, r espectively, we demonstrated layer-by-layer architecture of the particles. Polyanions with a shorter carboxyl/backbone distance tend to disassemble bi nary DNA/PLL complexes by displacing DNA while polyanions with a longer car boxyl/backbone distance effectively formed a tertiary complex. The zeta pot ential of such complexes became negative, indicating effective surface rech arging. The charge stoichiometry of the DNA/PLL/SPLL complex was found to b e close to 1:1:1, resembling polyelectrolyte complexes layered on macrosurf aces. Recharged particles containing condensed plasmid DNA may find applica tions as non-viral gene delivery vectors.