Lipid bilayers, which make up cell membranes, can change shape in response to external stimuli. To reproduce this behaviour in a synthetic system, Jan van Esch at Delft University of Technology in the Netherlands and his co-workers have produced a vesicle — a water-filled compartment bounded by a bilayer membrane — that forms and collapses in response to changes in pH.
The system comprises a solution containing a molecule with two 'tails', each of which can form reversible covalent bonds with another molecule. When there is a sufficiently high number of the molecules, the bonds form and the vesicles spontaneously take shape; conversely, when bonds break, the vesicles eventually collapse (pictured). The stability of the bonds is also affected by the solution's pH, with vesicles forming at a pH of more than 7, and dissociating completely when pH falls below 4.
These reversible vesicles might be useful for applications that require controlled encapsulation and delivery.
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Vesicles form with pH shift. Nature 471, 550 (2011). https://doi.org/10.1038/471550c
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DOI: https://doi.org/10.1038/471550c