Out-of-Plane Nanoscale Reorganization of Lipid Molecules and Nanoparticles Revealed by Plasmonic Spectroscopy.

Matthew R Cheetham,Jeremy J Baumberg,Rohit Chikkaraddy,Bart De Nijs,Stephen D Evans,Jack Griffiths,George R Heath

doi:10.1021/acs.jpclett.0c00182

Matthew R Cheetham, Jeremy J Baumberg + Show 5 more

Open Access

https://doi.org/10.1021/acs.jpclett.0c00182

Copy DOI

Abstract

Lipid bilayers assembled on solid substrates have been extensively studied with single-molecule resolution as the constituent molecules diffuse in 2D; however, the out-of-plane motion is typically ignored. Here we present the subnanometer out-of-plane diffusion of nanoparticles attached to hybrid lipid bilayers (HBLs) assembled on metal surfaces. The nanoscale cavity formed between the Au nanoparticle and Au film provides strongly enhanced optical fields capable of locally probing HBLs assembled in the gaps. This allows us to spectroscopically resolve the nanoparticles assembled on bilayers, near edges, and in membrane defects, showing the strong influence of charged lipid rafts. Nanoparticles sitting on the edges of the HBL are observed to flip onto and off of the bilayer, with flip energies of ∼10 meV showing how thermal energies dynamically modify lipid arrangements around a nanoparticle. We further resolve the movement of individual lipid molecules by doping the HBL with low concentrations of Texas Red (TxR) dye-labeled lipids.

Highlights

NPs either rupture through the cell membrane furnishing their use as therapeutic agents[4] and inducing cytotoxicity[5,6] or rest on the membrane providing imaging capabilities. These contradictory behaviors are linked to the different chemical and physical properties of NPs within membranes.[7−9]
We use hybrid lipid bilayers (HBLs) as model systems and study their interaction with AuNPs to develop tools to better understand the nanoscale inhomogeneity of HBLs12,13 and the complex diffusion of NPs on such surfaces.[14,15]
The diffusivities of mobile NPoMs remain unchanged for different dark-field white-light intensities (Figure S11). This shows that the optical absorption of NPoMs has negligible effects on the diffusion dynamics measured here

Summary

Corresponding Authors

Cheetham − NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom. Jack Griffiths − NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom. Bart de Nijs − NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom. Heath − School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom; orcid.org/00000001-6431-2191. Evans − School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom.

■ ACKNOWLEDGMENTS

Findings

■ REFERENCES