Stimuli-responsive liposome fusion mediated by gold nanoparticles

We report a new approach to controlling the fusion activity of liposomes by adsorbing carboxyl-modified gold nanoparticles to the outer surface of phospholipid liposomes. The bound gold nanoparticles can effectively prevent liposomes from fusing with one another at neutral pH value, while at acidic environments (e.g., pH < 5), the gold particle stabilizers will detach from the liposomes, with liposome fusion activity resuming. The binding of carboxyl-modified gold nanoparticles to cationic phospholipid liposomes at neutral pH and detaching at acidic pH values are evaluated and confirmed by dynamic light scattering, electron microscopy, fluorescence and UV-vis absorption experiments. The relative fusion efficiency of gold-nanoparticle- stabilized cationic liposomes with anionic liposomes is ∼25% at pH = 7 in contrast to ∼80% at pH = 4. Since liposomes have been extensively used as drug nanocarriers and the infectious lesions on human skin are typically acidic with a pH < 5, these acid-responsive liposomes with tunable fusion ability hold great promise for dermal drug delivery to treat a variety of skin diseases such as acne vulgaris and staph infections.