Nanometric Phase Transitions on Phospholipid Membranes Using Plasmonic Heating of Single Gold Nanoparticles

Abstract

Lately impressive advances have been made revealing the structure and pathways of cellular and subcellular systems by optical techniques with nanometric resolution [1]. Full understanding of the function of these systems requires additional energetic information of the processes involved. In order to obtain such information locally, it is necessary to develop remotely controlled nanoscale heat sources.We demonstrate the capability of single gold nanoparticles as optically controlled nanoscopic sources of heat. Gold nanoparticles attached to giant unilamellar vesicles in the gel-phase can induce reversible, local phase transitions to the fluid-phase when illuminated at their plasmon resonance [2]. The optically heated nanoparticles melt a nanoscale region of the membrane and exhibit an enhanced diffusion over the membrane. The diffusion is analyzed by single particle tracking for various phospholipids and laser power densities. As a result, we can control the nanoscale phase transition and obtain local information on the dynamics of the membrane.The results illustrate the use of single gold nanoparticles for local nanoscale thermodynamic investigations on phospholipid membranes. The approach presented here can be easily extended by combining it with other microscopy methods and optical tweezers techniques. This may also open new possibilities to position nanoparticles on cell membranes and thermally manipulate biomolecules or membrane processes.[1] R. Schmidt, C. A. Wurm, S. Jakobs, J. Engelhardt, A. Egner and S.W. Hell, Nat. Methods (2008) 5, 539[2] A.S. Urban et al., Nanoletters (2009) 9, 2903-2908