Engineering Magnetic Micro-and Nanorobots for Biomedicine

Engineering robots at the cellular scale could allow us to gain new insights into disease development and provide more targeted means for diagnostic and therapeutic interventions. Magnetic fields have proven to serve as safe strategy to wirelessly power magnetic microrobots for remote control in physiological environments. In this talk I will give an overview of three distinct examples of magnetic micro-and nanorobots for biomedical applications and describe their respective design and control schemes.<br/><br/>First, I will present a method for 3D spatiotemporal probing of tissue models from a single cell perspective using microrobots. We fabricated rod-shaped magnetic microrods and leveraged 3D magnetic field generation, physical modeling, and image analysis to reveal local shear moduli and remotely apply mechanical stimuli [1]. The heterogenous mechanical landscape of a tumor’s extracellular matrix (ECM) is in part a result of increased local release of enzymes, in particular certain proteases, which degrades the ECM and is associated with tumor invasion. In a next example, I will describe nanorobots that are either activated or detected via magnetic fields and designed to report a tumor’s proteolytic activity as novel diagnostic [2].<br/><br/>Last, I will show how an individual, synthetic and swarms of living magnetic microbots can help to locally enhance transport of nanoparticles (NPs) mimicking drug carriers in a tissue model [3]. We employed two distinct micropropeller designs powered by rotating magnetic fields to increase diffusion-limited transport of NPs by enhancing local fluid convection. In the first approach, we use a single synthetic magnetic microrobot called an artificial bacterial flagellum, and in the second approach, we control swarms of magnetotactic bacteria to create a directable “living ferrofluid” by exploiting ferrohydrodynamics. With both strategies, we demonstrated the ability to locally and wirelessly drive convective transport in tissue models. The latter strategy has also shown to outperform synthetic ferrofluids in terms of ferrohydrodynamic coupling to drive NP transport (Fig.1) [4]. Lastly, I will share insights into how these living magnetic microrobots can be further engineered to function as therapeutic vectors themselves that can be magnetically controlled [5].<br/><br/><b>References</b><br/>[1] Asgeirsson et al.,<i>Lab Chip</i><b>, <b>21</b>,</b> 3850-3862, 2021<br/>[2] Schuerle et al. <i>Nano Lett.</i>, 16, 10, 6303-6310, 2016<br/>[3] Schuerle et al., <i>Sci. Adv.</i>, vol. 5, no. 4, eaav4803, 2019<br/>[4] Mirkhani, et al, <i>Adv. Funct. Mater.</i>, 2003912, 2020<br/>[5] Gwisai et al, bioRxiv, doi.org/10.1101/2022.01.03.473989, 2022