High-Resolution Patterned Delivery of Chemical Signals From 3D-Printed Picoliter Droplet Networks.

Synthetic cells, such as giant unilamellar vesicles, can be engineered to detect and release chemical signals to control target cell behavior. However, control over the targeting of cell populations is limited due to poor spatial or temporal resolution and the inability of synthetic cells to deliver patterned signals. Here, 3D-printed picoliter droplet networks are described that direct gene expression in underlying bacterial populations by patterned release of a chemical signal with temporal control. Shrinkage of the droplet networks prior to use achieves spatial control over gene expression with ≈50 µm resolution. Ways to store chemical signals in the droplet networks and to activate release at controlled points in time are also demonstrated. Finally, it is shown that the spatially-controlled delivery system can regulate competition between bacteria by inducing the patterned expression of toxic bacteriocins. This system provides the groundwork for the use of picoliter droplet networks in fundamental biology and in medicine in applications that require the controlled formation of chemical gradients (i.e., for the purpose of local control of gene expression) within a target group of cells.