Invited Paper
Optothermal Manipulation of Cells with Plasmonic Nanoparticles

Light absorbed by plasmonic nanoparticles is very efficiently converted into heat. Gold particles, for example, can reach temperatures up to several hundred degrees centigrade within nanoseconds when they are irradiated with a focused laser beam at their plasmon resonance frequency. A single gold nanoparticle can thus be used as a fine tool to apply heat to a nanosopic area which opens the door to exciting experimental applications were temperature sensitive biological processes can be studied in great detail and with unprecedented resolution.

As an example, I will show how plasmonic heating can be applied to control the permeability of cell membranes. Lipid bilayers are almost impermeable to charged molecules and ions which, under normal circumstances, can only pass the membrane barrier with the help of specialized transport proteins. The physical properties of lipid membranes, however, are also affected by local temperature changes. In our experiment, we probe the temperature dependent permeability of a bilayer membrane in absence of any carrier proteins or ion channels. Single gold nanoparticles are used as small, localized sources of heat. Adjusting the nanoparticle temperature renders it possible to reversibly alter the bilayer resistance and ion current across the membrane. Shifting to real cells, we could show that gold nanoparticles can also be injected into living cells by a combination of temperature and optical force.

Overall, these results illustrate how plasmonic heating can be employed to achieve nanoscale control over biological systems and to actively deliver nanoscopic objects into living cells, which paves the way for future biomedical applications in nanotheranostics and drug delivery.

t.lohmueller@lmu.de