Michael Christiansen


Last Name

Christiansen

First Name

Michael

ORCID

0000-0002-6420-1616

Organisational unit

09619 - Schürle-Finke, Simone / Schürle-Finke, Simone

Filters

2023 - 20253
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Publications 1 - 3 of 3
  • Untethered: using remote magnetic fields for regenerative medicine
    Item type: Review Article
    Chansoria, Parth; Liu, Hao; Christiansen, Michael; et al. (2023)
    Trends in Biotechnology
    Magnetic fields are increasingly being used for the remote, noncontact manipulation of cells and biomaterials for a wide range of regenerative medical (RM) applications. They have been deployed for their direct effects on biological systems or in conjunction with magnetic materials or magnetically tagged cells for a targeted therapeutic effect. In this work, we highlight the recent trends on the broad use of magnetic fields for the homing of therapeutic cells and particles at targeted tissue sites, biomimetic tissue fabrication, and control of cell fate and proliferation. We also survey the design and control principles of magnetic manipulation systems, including their capabilities and limitations, which can guide future research into developing more effective magnetic field-based regenerative strategies.
  • Engineering bacterial-based biohybrid microrobots for magnetic torque-driven control
    Item type: Journal Article
    Regazzoni , Lisa; Totter , Elena; Menghini , Stefano; et al. (2025)
    Cell Reports Physical Science
    Biohybrid microrobots combine living organisms with synthetic nanomaterials, unlocking new possibilities in micromanipulation. Magnetic functionalization enables their remote control, complementing innate sensing and taxis. While most bacterial-based microrobots primarily rely on magnetic directing- or gradient-based pulling fields, rotating magnetic fields (RMFs) provide torque-driven, feedback-free navigation with superior energy transfer and deeper tissue penetration. Nevertheless, previous designs prioritized steering or pulling over continuous torque actuation and commonly featured limited nanoparticle coverage. Here, we develop a high-throughput method to covalently attach ∼1,000 magnetic nanoparticles per Escherichia coli cell, generating sufficient anisotropy for rotational actuation at several hertz. Steric hindrance from lipopolysaccharides is mitigated by reversible calcium complexation. Functionalization under a directing magnetic field further enhances torque and responsiveness, consistent with simulations indicating that increased anisotropy can outperform higher particle loading. In 3D tumor spheroids, these biohybrid microrobots displayed 5-fold increase in colonization under RMF exposure, underscoring the potential of torque-based functionalization for magnetic micromanipulation.
  • Spatially selective delivery of living magnetic microrobots through torque-focusing
    Item type: Journal Article
    Mirkhani, Nima; Christiansen, Michael; Gwisai, Tinotenda; et al. (2024)
    Nature Communications
    Rotating magnetic fields enable biomedical microrobots to overcome physiological barriers and promote extravasation and accumulation in tumors. Nevertheless, targeting deeply situated tumors requires suppression of off-target actuation in healthy tissue. Here, we investigate a control strategy for applying spatially selective torque density to microrobots by combining rotating fields with magnetostatic selection fields. Taking magnetotactic bacteria as diffuse torque-based actuators, we numerically model off-target torque suppression, indicating the feasibility of centimeter to millimeter resolution for human applications. We study focal torque application in vitro, observing off-target suppression of actuation-dependent effects such as colonization of bacteria in tumor spheroids. We then design and construct a mouse-scale torque-focusing apparatus capable of maneuvering the focal point. Applying this system to a mouse tumor model increased accumulation of intravenously injected bacteria within tumors receiving focused actuation compared to non-actuated or globally actuated groups. This control scheme combines the advantages of torque-based actuation with spatial targeting.
Publications 1 - 3 of 3