Complexes of star-shaped cationic polyelectrolytes with anionic liposomes: Towards multi-liposomal assemblies with controllable stability

Abstract

Complexes were formed via the electrostatic interaction between 30–50 nm anionic liposomes and a star-shaped polyelectrolyte, poly{[2-(methacryloyloxy)ethyl]trimethyl ammonium iodide}, having cationic arms that radiate from a silicon-based central core. The complexation was investigated with attention given to assessing the capacity of the cationic stars for the anionic liposomes (both liquid and solid); the integrity of the complexed liposomes; and the stability of the resulting star/liposome complexes in aqueous salt solutions. We have found that by changing the content of anionic groups in the liposomal membrane as well as the phase-state of membrane, the stability of star/liposome complexes in aqueous salt media can be controlled. The liquid liposomes with 0.1 mol fraction of anionic palmitoyloleoylphosphatidylserine (POPS1−), and solid liposomes with 0.1 mol fraction of POPS1−, retain their integrity when bound to the stars, with the resulting star/liposome complexes being stable in physiological solution, i.e. [NaCl] = 0.15 M. Multi-liposomal complexes containing up to 12 liposomes per star seem to hold promise as carriers for biologically active compounds.