Mapping of the field distribution around dielectrophoretically aligned cells by means of small particles as field probes

Abstract

For the prediction of the conditions of electrofusion knowledge about the strength and divergence of the local field around dielectrophoretically aligned cells is required. Bacteria and chloroplasts (showing positive dielectrophoresis) as well as polystyrene and glass beads (exhibiting negative dielectrophoresis) are used as small probes for the field line distribution generated by aligned plant protoplasts. The biological particles gather at the poles of terminal protoplasts and close to the contact zones of adhered protoplasts in the chain, whereas the artificial beads form concentric rings around the individual aligned protoplasts. The position of these concentric rings and of bacterial assembly depends on the volume of the aligned protoplasts and on their location in the chain. These phenomena occur at much lower field strengths than those required for the alignment of these particles in the absence of protoplasts. This suggests that the field strength and the inhomogeneity close to the contact zone of aligned protoplasts may be considerably higher than in the external space. This may also explain why symmetric breakdown leading to fusion can occur in both hemispheres of aligned cells despite the fact that in freely suspended cells an asymmetric breakdown is observed under the experimental conditions.