Engineering Magnetotactic Bacteria as Medical Microrobots.

Nature's ability to create complex and functionalized organisms has long inspired engineers and scientists to develop increasingly advanced machines. Magnetotactic bacteria (MTB), a group of Gram-negative prokaryotes that biomineralize iron and thrive in aquatic environments, have garnered significant attention from the bioengineering community. These bacteria possess chains of magnetic nanocrystals known as magnetosomes, which allow them to align with Earth's geomagnetic field and navigate through aquatic environments via magnetotaxis, enabling localization to areas rich in nutrients and optimal oxygen concentration. Their built-in magnetic components, along with their intrinsic and/or modified biological functions, make them one of the most promising platforms for future medical microrobots. Leveraging an externally applied magnetic field, the motion of MTBs can be precisely controlled, rendering them suitable for use as a new type of biohybrid microrobotics with great promise in medicine for bioimaging, drug delivery, cancer therapy, antimicrobial treatment, and detoxification. This mini-review provides an up-to-date overview of recent advancements in MTB microrobots, delineates the interaction between MTB microrobots and magnetic fields, elucidates propulsion mechanisms and motion control, and reports state-of-the-art strategies for modifying and functionalizing MTB for medical applications.