Speaker
Description
Stimuli-responsive supramolecular materials are smart materials whose molecular organization, and consequently their properties can be controlled using external triggers such as temperature, pH, and light. In recent years, significant efforts have been devoted into developing active liposomes with precisely controllable structural properties. These systems can be leveraged for the programmable transport and delivery of molecular cargoes, such as drugs, as well as for applications in synthetic biology. Among these, pH responsive vesicles are particularly attractive as they can respond to pH gradients that exist in biological environments. pH variations trigger changes in the designed constituent molecular units, leading to vesicle disassembly and cargo release. Despite considerable progress, active self-assembly of liposomes are rarely reported and active liposomes that are capable of programmable assembly-disassembly in response to stimuli are scarce. In this study, phospholipids are formed in-situ from simple molecular precursors and are made active through their pH responsiveness. The dynamic nature of imine bonds, makes the lipids and their vesicular assemblies responsive to pH changes in the environment. Since imine bonds are stable at neutral pH but dissociates under acidic conditions, lowering the pH leads to breakdown of vesicles and release of encapsulated molecules into the surroundings. By employing Gluconolactone, which slowly hydrolyzes into gluconic acid, a temporally programmable vesicle disassembly has been achieved. Notably, vesicle actively assemble and disassemble as the cycle can be repeated by switching the pH, establishing a key feature of responsive systems. Furthermore, the vesicles exhibit diameters of approximately 200 nm, placing them within the optimal size range for drug delivery applications. Combined with its pH responsiveness, this feature gives the minimal chemical design strong potential to develop pH responsive active drug delivery systems. In addition, this dynamic system closely mimics the adaptive behaviour of biological structures, providing a platform to better understand the operation of such complex mechanisms.
