Onion-like vesicle for drug delivery

A drug delivery vesicle akin to an onion has been developed by researchers at the University of Pennsylvania. The team have discovered that a certain kind of dendrimer – a molecule with tree-like branches – offers a simple way of creating vesicles, and tailoring their diameter and thickness. Additionally, these vesicles self-assemble with concentric layers of membranes, much like an onion. The study – led by Professor Virgil Percec – focussed on Janus dendrimers, a class of molecules with two faces, each tree-like, rather than the head and tail found in molecules that make up biological membranes. These molecules are amphiphilc, meaning one face is hydrophobic and one is hydrophilic. It builds on work by Percec in 2010 in which he discovered that dissolving Janus dendrimers in an alcohol solution and injecting them into water formed stable, evenly sized vesicles, but producing vesicles with multiple bilayers was difficult. "The only way it has been achieved in the past was through a complicated mechanical process, which was a dead end," Percec said. "This was not a viable option for mass-producing multilayered vesicles, but, with our library of amphiphilic Janus dendrimers, we were lucky to find some molecules that have in their chemicals instructions needed to self-assemble into these very beautiful structures." [caption id="attachment_38725" align="alignright" width="200"] University of Pennsylvania researchers have shown that a certain kind of dendrimer, a molecule that features tree-like branches, offers a simple way of creating vesicles and tailoring their diameter and thickness. Moreover, these dendrimer-based vesicles self-assemble with concentric layers of membranes, much like an onion. Here, black and white CryoTEM images of the vesicles were turned into colourised 3-D models to better show their layers. Credit: University of Pennsylvania[/caption] The team tested different dendrimers with different organic solvents and found they could produce these onion-like structures and control the number of layers they contained. By altering the concentration of the dendrimers in solution, they could produce vesicles with as many as 20 layers when the solution was introduced to water. This opens up the possibility of releasing drugs over time, with a new dose in each layer, or even a cocktail of drugs in a different layer so each is released in sequence. "If you want to deliver a single drug over the course of 20 days, you could think about putting one dose of the drug in each layer and have it released over time," Percec said. "Or you might put one drug in the first layer, another drug in the second and so on. Being able to control the diameter of the vesicles may also have clinical uses; target cells might only accept vesicles of a certain size."