Understanding Light-Responsive Release from Liquid Crystal Nanoparticles

Stimuli-responsive materials are crucial to advance delivery systems for drugs and catalysts, where a targeted response would grant control in the time and location of delivery. We have recently demonstrated the first example of light-responsive cubic lyotropic liquid crystal (LLC) lipid dispersions, or cubosomes, for on-demand release of entrapped guest molecules. In these systems, photoswitchable azobenzene photosurfactants (AzoPS) are light-responsive additives that impart structural control. Upon irradiation with light, the AzoPS within the cubosomes undergo trans-cis photoisomerisation, which leads to "squeezing" of the cubic lattice and release of entrapped cargo. However, the mechanism for photoisomerisation of azobenzene, especially in condensed, self-assembled states, and the knock-on effect this has on the long-range structural order, are still poorly understood. This knowledge is essential to inform the targeted, bottom-up design of next-generation systems where the light-response is harnessed for optimal control. The aim of this study is to use selective deuteration in small-angle neutron scattering (SANS) to understand where the photosurfactant resides in cubosomes containing AzoPS and the lipid monoolein (MO). We will then use this knowledge to explore how photoisomerisation affects the long-range structural order and release in these systems.