Emerging methods to control the delivery of small molecules have wide-spread applications spanning from pharmaceuticals, notably for COVID-19 mRNA vaccines, to catalytic reactions, agriculture, and food. Targeting the release of entrapped payloads, in response to an external stimulus, ensures that they are used in a direct manner, which can reduce waste or harmful side-effects. 

Lyotropic liquid crystals have well-defined internal structures suitable to entrap small-molecule payloads and can be broken up into low-viscosity dispersions, aiding their use as delivery systems. In this collaborative project between the Photoactive Materials group and the B21 beamline at Diamond Light Source, we demonstrate the first example of light-responsive cubic lyotropic liquid crystal dispersions, or cubosomes, using photoswitchable azobenzene surfactants to enable external control over the structure. Upon UV irradiation, the cubic lattice contracts, squeezing the entrapped payload out of the structure. The ability to control the internal liquid crystal structure using light, and the dramatic effect this has on the retention of entrapped molecules, suggests that these systems may have huge potential as the next generation of delivery devices for drugs or catalysts. 

Figure: Formation and release mechanism in light-responsive cubosomes. Azobenzene surfactants (AzoPS) are combined with a lipid, water and dye, mixed and broken up into a dispersion of particles with internal, cubic liquid crystal phases. On irradiation with UV light, the lattice contracts and squeezes out the entrapped dye particles.