Enhanced Optical Collection of Micro- and Nanovesicles in the Presence of Gold Nanoparticles

We describe a process for collecting micro- and nanovesicles on a glass substrate using the optical pressure of a laser beam. The laser beam was focused on a glass substrate that sandwiched a solution containing vesicles prepared using a phospholipid. The optical pressure generated at the surface of the vesicles pulled them into the center of the beam where they formed an aggregate on the glass surface. The vesicles prepared with a buffer solution were successfully collected via adsorption onto the glass surface, whereas the vesicles prepared with pure water exhibited no such tendency. The time required to collect a certain amount of vesicles was inversely proportional to their concentration. To enhance the collection efficiency, we added gold nanoparticles to the vesicle solution. The addition of gold nanoparticles into the solution reduced the collection time to one-tenth of that without it, and this was attributed to thermal mixing promoted by the heat generated by the absorption from the gold nanoparticles in the solution, as well as to an enhancement of light scattering induced by the gold nanoparticles. The optical collection of vesicles coupled with gold nanoparticles shows a promise for the collection of trace amounts of extracellular vesicles in biological fluids.