Date Published: November 28, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Oliver Nagel, Manuel Frey, Matthias Gerhardt, Carsten Beta.
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.
Cell Culture: D. discoideum AX2 wild‐type cells were cultivated in HL5 medium (Formedium, Norwich, England) at 22 °C on polystyrene Petri dishes (Sarstedt, Nümbrecht, Germany), or shaken in suspension at 150 rpm. Suspensions of 4 × 104 cells mL−1 and 1 × 104 beads mL−1 (single cell carrying a single bead), 6 × 106 cells mL−1 and 2 × 105 beads mL−1 (ibidi chamber), 1.5 × 106 cells mL−1 and 2 × 105 beads mL−1 (uncaging dish), 1.5 × 107 cells mL−1 and 2 × 107 beads mL−1 (uncaging in microchannel), 2 × 105 cells mL−1 (all other experiments) were used. Before the experiments of single cells carrying a single particle where carried out, the HL5 medium was renewed and cells and beads were distributed equally across the wells of a 24 well plate. The experiments started after an attachment time of 30 min. Prior to the other experiments, the cells were washed and transferred into 25 mL shaking phosphate buffer solution (150 rpm), composed of 14.6 mm KH2PO4 and 2 mm Na2HPO4 (Merck KGaA, Darmstadt, Germany) with a pH‐value of 6.0. In this solution the cell were starved. After ≈3 h (experiments in the gradient chamber and uncaging experiments in the microchannel and in the dish), or after ≈6 h (micropipette experiment and spontaneous aggregation experiments), or after ≈8 h (aggregation of the larger micro‐objects) the cells were centrifuged at 1000 rpm for 5 min (micropipette experiments), or 3 min (all other experiments). Afterwards, cells were mixed with a suspension of either polystyrene beads (Polysciences Europe GmbH, Hirschberg, Germany), or WGA coated agar beads (Bioworld, Dublin, OH 43 017, USA), or SU‐8 based micro‐objects to prepare them for the different experiments. For the photo uncaging experiments 10 µm BCMCM caged cAMP (BIOLOG Life Science Institute, Bremen, Germany) was added to the suspension. The cells were settled for 30 min inside the flow chambers or on the petri dishes to attach before the experiment was conducted.
The authors declare no conflict of interest.