Triggered interactions between nanoparticles and lipid membranes: design principles for gel formation or disruption-and-release.

Lipid bilayer vesicles offer exciting possibilities for stimulated response, taking advantage of the membrane's flexibility and impermeability. We show how synergistic interactions between vesicles and polymer-based nanoparticles can be triggered at the nanoscale using UV light. This interaction leads either to adhesion and a membrane-based gel, or to nanoscale wrapping of the particles by the membrane and then vesicle destruction. To map the response, we varied the particle-membrane interactions via their surface charge densities. We found a crossover from adhesion to destruction at a well-defined region in parameter space. We modeled these results by accounting for the electrostatic attraction and the energy of membrane bending. We then synthesized amphiphilic polymers containing a UV-responsive nitrobenzyl moiety that switches its charge, and showed how a trigger predictably led to either a vesicle gel or disruption and release. The results pave the way to a new triggering mechanism and new response modes in soft materials.