ACS Nano (2013)

The surfaces of bones undergo continual restructuring as osteoclast cells pick up debris and osteoblast cells deposit new material. Inspired by this process, Anna Balazs and co-workers at the University of Pittsburgh have now devised a self-assembled lipid vesicle that can pick up nanoparticles from a surface and then drop them off at a different and controlled location.

Using dissipative particle dynamics simulations — a method similar to molecular dynamics but that also takes into account the hydrodynamics of the system — the researchers show that a lipid bilayer vesicle can be pushed along a hydrophilic surface by an imposed shear flow of a hydrophilic solvent. When the vesicle encounters a Janus particle exposing its hydrophobic side to the solution, it can incorporate the particle in its membrane structure detaching it from the surface. A vesicle with a diameter of 10 nm can pick up four particles that are around three times smaller than itself without breaking apart. The Janus particles can then be dropped off when the vesicle encounters a suitably sticky surface.