LAUSR

The unique multicompartmental nanostructure of lipid-based mesophases can be triggered, on-demand, in order to control the release of encapsulated drugs. In this study, these nanostructured matrices have been designed to respond to a specific enzyme, invertase, an enzyme which catalyses the hydrolysis of sucrose. The effect of two sugar esters upon the phase behaviour of two different lipids which form cubic phases, phytantriol and monolinolein, was investigated. Factors affecting the hydrolysis of the sucrose headgroup are discussed in terms of the molecular structure of the sugar surfactant and also its ability to incorporate into the lipid bilayer. By hydrolysing the incorporated sugar esters, a dynamic change in mesophase nanostructure from vesicles to a cubic phase was observed. This phase change resulted in the triggered release of an encapsulated model drug, fluorescein. This investigation demonstrates, for the first time, that changes on a molecular level by subtly controlling the hydrophilic and hydrophobic features of an amphiphilic additive at the interface by enzymatic hydrolysis can result in a global change in the system and so paves the way towards the design and development of lipid-based matrices which are responsive to specific enzymes for the controlled delivery of pharmaceutically active molecules or functional foods.