Label-Free Time-Resolved Monitoring of Photolipid Bilayer Isomerization by Plasmonic Sensing

The photo-isomerization of the photolipid azo-PC, a derivative of phosphatidylcholine containing an azobenzene group in its sn2 acyl chain, enables optical control over key properties of supported lipid bilayers (SLBs), such as membrane fluidity and bilayer thickness. However, azobenzenes are well-known for their interaction with various dyes through photo-modulation and -sensitization pathways, presenting a challenge in bilayer characterization by fluorescence microscopy. Label-free tools capable of monitoring the switching process of photolipid SLBs at the nanoscale are therefore highly desired. In this study, the use of dark field scattering spectroscopy on gold nanorods as a highly sensitive approach is demonstrated for analyzing the reversible photo-isomerization dynamics of photolipid SLBs in real time at the single particle level. Photoswitchable lipid azo-PC, which undergoes photoisomerization between trans and cis states by illumination of UV and blue light, enables optical control over membrane properties of supported lipid bilayers. Here, plasmonic nanorods are used as a label-free and highly sensitive tool to monitor the reversible photoisomerization dynamics of photolipid supported lipid bilayers. image