Langmuir 32, 3794–3802 (2016)

Microtubules — the cell's cytoskeleton formed through the polymerization of tubulin proteins — are important for cell morphogenesis, movement and protein transport. Tubulin has been encapsulated in giant liposomes and shown to polymerize and form protrusions similar to those produced by living cells. However, repeated and controlled formation of these protrusions has not been possible. Researchers in Japan now report that applying hydrostatic pressure can reversibly and repeatedly alter the polymerization and depolymerization of microtubules inside liposomes, forming artificial motile cell models for molecular robotics.

Kingo Takiguchi and co-workers — from Nagoya University, Kyoto University and the University of Tokyo — encapsulated tubulin inside giant liposomes and used microscopy to monitor the morphological changes at different hydrostatic pressures. At ambient pressure (0.1 MPa), tubulin was seen to polymerize, elongate and push the liposomal membrane outward to form protrusions. When the pressure was increased to 60 MPa, the protrusions shortened rapidly but were regenerated at the same location within several minutes of the pressure being released. This process was induced several times, suggesting that microtubules are sensitive to hydrostatic pressure and reversible deformation can be exploited to control their polymerization state.