Influence of the magnetic field on the two-dimensional control of Magnetospirillum gryphiswaldense strain MSR-1

Magnetotactic bacteria have the potential to controllably reach deep-seated regions of the body via vessels and achieve targeted drug delivery. In this application, motion of the magnetotactic bacteria is influenced by the strength of the external magnetic field. Here, we investigate the swimming characteristics of magnetotactic bacteria (Magnetospirillum gryphiswaldense strain MSR-1) under the influence of uniform and adaptive magnetic fields inside microfluidic chip with depth of 5 µm. This depth enables tracking of single bacterium and comparison of uniform and adaptive magnetic field on the positioning accuracy. We find that under the influence of magnetic field reversal with approximately twice the field strength, the diameter of the U-turn trajectories taken by the magnetotactic bacteria is decreased by 63%. In addition, the adaptive magnetic field decreases the size of region-of-convergence of the controlled bacteria within the vicinity of the reference position by 65.5%, compared to control using uniform magnetic field. The comparisons between motion control using uniform and adaptive magnetic fields are done on the same culture of magnetotactic bacteria and using the same cell in each motion control trial.