Towards Mechanically-Activated Artificial Cell

Artificial cells are minimal and well-defined systems that can be used to decipher the design principles behind biological complexity. One current platform for building artificial cells involve the encapsulation of in vitro transcription-translation system in compartmentalized structures such as single or double emulsions or lipid vesicles. Information is encoded in artificial cells through the use of gene circuits and the control of artificial cells has largely been limited to the addition of membrane-permeable small molecule inducers. To expand the capability of information processing by artificial cells, we seek to construct artificial cells that can respond to mechanical forces, which are arguably the most primitive sensory information cells can perceive. As a model of artificial cells, we generated double emulsion droplets with surfactant-stabilized oil in the middle phase. We developed a multilayer microfluidic device capable of trapping individual double emulsion droplet, and apply controlled aspiration and compression to the trapped droplet to simulate different mechanical loading on an artificial cell. We demonstrated the salient features of this single droplet manipulation device and showed that aspiration of the middle phase oil can lead to thinning of the oil. By encapsulating mammalian cell free expression system encoding a calcium biosensor, we show that thinning of oil combined with hypoosmotic shock can lead to calcium influx into the artificial cell. The transport of calcium ions through otherwise impermeable oil represents an advance in artificial cell research and opens up a new dimension in artificial cell activation using a mechanical stimulus.