Droplet based synthetic biology: chemotaxis and interface with biology

Life-like behaviors such as fission, fusion and movement can be artificially re-created exploiting highly simplified protocell systems. This thesis is mainly focused on chemotaxis protocell systems and their integration with biological systems in order to show potential future applications. 1-Decanol droplets, formed in an aqueous medium containing decanoate at high pH, become chemotactic when a chemical gradient is placed in the external aqueous environment. We investigated the behavior of these droplets, their ability to transport and deposit living and non-living objects and to interface them with biofilms. To make the artificial system compatible with natural living systems we developed a partially hydrophobic alginate capsule as a protective unit that can be precisely embedded in a droplet, transported along chemical gradients and deposited. We developed a system that was able to transport: Escherichia coli, Bacillus subtilis and Saccharomyces cerevisiae. Both bacteria survived the transport. However, yeast survived but not in a consistent and repeatable way. Next, we evolved the system to transport human cell lines. We found that A549 cells survive encapsulation but not the transport. A549 cells are in fact very sensitive to toxic 1-decanol. We however found out that this cell line secretes compounds able to decrease the surface tension and to increase the capsule-droplet affinity. Finally we discuss future solutions for the effective transport of human cells.