Harnessing Motile Amoeboid Cells as Trucks for Microtransport and ‐Assembly

Abstract Cell‐driven microtransport is one of the most prominent applications in the emerging field of biohybrid systems. While bacterial cells have been successfully employed to drive the swimming motion of micrometer‐sized cargo particles, the transport capacities of motile adherent cells remain largely unexplored. Here, it is demonstrated that motile amoeboid cells can act as efficient and versatile trucks to transport microcargo. When incubated together with microparticles, cells of the social amoeba Dictyostelium discoideum readily pick up and move the cargo particles. Relying on the unspecific adhesive properties of the amoeba, a wide range of different cargo materials can be used. The cell‐driven transport can be directionally guided based on the chemotactic responses of amoeba to chemoattractant gradients. On the one hand, the cargo can be assembled into clusters in a self‐organized fashion, relying on the developmentally induced chemotactic aggregation of cells. On the other hand, chemoattractant gradients can be externally imposed to guide the cellular microtrucks to a desired location. Finally, larger cargo particles of different shapes that exceed the size of a single cell by more than an order of magnitude, can also be transported by the collective effort of large numbers of motile cells.


Supporting Movies
Movie S1: Cells moving randomly on a glass plate. When cells collide with a microbead, the bead stays attached to the cell and is carried along. Experiments have been conducted in HL5 medium in a Petri dish. For image acquisition we used an Olympus IX71 microscope with an ORCA-Flash 4.0 camera and 20x magnification. We took one image every 20 seconds, time is displayed in hours and minutes (hh:mm). Movie S5: Cells moving in a cAMP gradient inside an ibidi "µ-Slide Chemotaxis" chamber.
The cAMP concentration increases from 0 (right) to 10µM (left) over a distance of 1 mm, see also Figure S2. On their way, the cells pick up microparticles and carry them along. For image acquisition we used an Olympus IX71 microscope with an ORCA-Flash 4.0 camera and 10x magnification. We took one image every 30 seconds, time is displayed in hours and minutes (hh:mm).
3 Movie S6: Cells moving on a glass plate towards a laser spot where cAMP is released by photo-uncaging. Experiments have been conducted in phosphate buffer containing 10µM BCMCM-cAMP in a glass bottom Petri dish. For image acquisition we used an Olympus IX71 microscope with an Olympus XM 10 camera and 20x magnification. We took one image every 30 seconds, time is displayed in hours and minutes (hh:mm).
Movie S7: Cells transporting microbeads into a narrow side channel towards a laser spot where cAMP is photo-chemically released. Experiments have been conducted in phosphate buffer containing 10µM BCMCM-cAMP. For image acquisition we used an Olympus IX71 microscope with an Olympus XM 10 camera and 20x magnification. We took one image every 30 seconds, time is displayed in hours and minutes (hh:mm).
Movie S8: Cells and cell aggregates transporting microbeads into a narrow side channel towards a laser spot where cAMP is photo-chemically released. Experiments have been conducted in phosphate buffer containing 10µM BCMCM-cAMP. For image acquisition we used an Olympus IX71 microscope with an Olympus XM 10 camera and 20x magnification.
We took one image every 30 seconds, time is displayed in hours and minutes (hh:mm).
Movie S9: Cells streaming and aggregating on a glass plate towards a laser spot where cAMP is photo-chemically released. While aggregating, the cells transport and assemble microobjects of different size and shape. Experiments have been conducted in phosphate buffer containing 10µM BCMCM-cAMP inside a custom-made microchamber, see Figure S1.
For image acquisition we used an Olympus IX71 microscope with a Hamamatsu R² camera and 10x magnification. We took one image every 30 seconds, time is displayed in hours and minutes (hh:mm).
Movie S10: Cells and cell clusters migrating towards a micropipette filled with a solution of 100µM cAMP. While aggregating at the pipette tip, they transport and assemble microobjects of different size and shape. Experiments have been conducted in phosphate buffer in a Petri dish. For image acquisition we used an Olympus BX51WI microscope with a Hamamatsu R² camera and 4x magnification. We took one image every 30 seconds, time is displayed in hours and minutes (hh:mm).