Near-surface effects on the controlled motion of magnetotactic bacteria

摘要

Magnetotactic bacteria have the potential to controllably reach stagnant fluids inside the human body and achieve targeted drug delivery. In this application, motion of the magnetotactic bacteria is influenced by the near-surface effects such as the background flows and surface interactions. Here, we provide a hydrodynamic model of bipolarly-flagellated magnetotactic bacteria (Magnetospirillum gryphiswaldense strain MSR-1) based on the resistive-force theory to resemble the helical body and the two flagella bundles, and investigate their swimming characteristics in two environments, i.e., free-space and near flat walls. The free-space is studied using capillary tubes with depth of 200 μm, whereas the effect of the flat walls is investigated using microfluidic chips with depth of 5 μm. We find that the linear speeds of bacteria near- and far-surface are 36±16.4 μm/s (mean±s.d.) and 46±6.8 μm/s, respectively, whereas their respective angular velocities are 12.5±5.7 rad/s and 13.5±5.0 rad/s.