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Magnetic Actuation Methods in Bio/Soft Robotics

Sequential Magneto-Actuated and Optics-Triggered Biomicrorobots for Targeted Cancer Therapy

Magnetic iron oxide nanoparticles (IONPs) have wide applications in magnetic resonance imaging (MRI), biomedicine, drug delivery, hyperthermia therapy, catalysis, magnetic separation, and others However, these applications are usually limited by irreversible agglomeration of IONPs in aqueous media because of their dipole-dipole interactions, and their poor stability A protecting polymeric shell provides IONPs with not only enhanced long-term stability, but also the functionality of polymer shells Therefore, polymer-grafted IONPs have recently attracted much attention of scientists In this tutorial review, we will present the current strategies for grafting polymers onto the surface of IONPs, basically including "grafting from" and "grafting to" methods Available functional groups and chemical reactions, which could be employed to bind polymers onto the IONP surface, are comprehensively summarized Moreover, the applications of polymer-grafted IONPs will be briefly discussed Finally, future challenges and perspectives in the synthesis and application of polymer-grafted IONPs will also be discussed

Surface engineering of magnetic iron oxide nanoparticles by polymer grafting: synthesis progress and biomedical applications

Microrobots driven by multiple propelling forces hold great potential for noninvasively targeted delivery in the physiologic environment. However, the remotely collective perception and precise propelling in a low Reynold's number bioenvironment remain the major challenges of microrobots to achieve desired therapeutic effects in vivo. Here, we reported a biohybrid microrobot that integrated with magnetic, thermal, and hypoxia sensitivities and an internal fluorescent protein as the dual reporter of thermal and positioning signals for targeted cancer treatment. There were three key elements in the microrobotic system, including the magnetic nanoparticle (MNP)-loaded probiotic Escherichia coli Nissle1917 (EcN@MNP) for spatially magnetic and hypoxia perception, a thermal-logic circuit engineered into the bacteria to control the biosynthesis of mCherry as the temperature and positioning reporter, and NDH-2 enzyme encoded in the EcN for enhanced anticancer therapy. According to the fluorescent-protein-based imaging feedback, the microrobot showed good thermal sensitivity and active targeting ability to the tumor area in a collective manner under the magnetic field. The cancer cell apoptosis was efficiently triggered in vitro and in vivo by the hybrid microrobot coupled with the effects of magnetothermal ablation and NDH-2-induced reactive oxygen species (ROS) damage. Our study demonstrates that the biohybrid EcN microrobot is an ideal platform to integrate the physical, biological, and chemical properties for collective perception and propelling in targeted cancer treatment.

An Engineered Bacteria-Hybrid Microrobot with the Magnetothermal Bioswitch for Remotely Collective Perception and Imaging-Guided Cancer Treatment.

Nanomotor-based adsorbent for blood Lead(II) removal in vitro and in pig models.

Micro-/nanomotors are widely used in micro-/nanoprocessing, cargo transportation, and other microscale tasks because of their ability to move independently. Many biological hybrid motors based on bacteria have been developed. Magnetotactic bacteria (MTB) have been employed as motors in biological systems because of their good biocompatibility and magnetotactic motion in magnetic fields. However, the magnetotaxis of MTB is difficult to control due to the lack of effective methods. Herein, a strategy that enables control over the motion of MTB is presented. By depositing synthetic Fe3 O4 magnetic nanoparticles on the surface of MTB, semiartificial magnetotactic bacteria (SAMTB) are produced. The overall magnetic properties of SAMTB, including saturation magnetization, residual magnetization, and blocking temperature, are regulated in a multivariate and multilevel fashion, thus regulating the magnetic sensitivity of SAMTB. This strategy provides a feasible method to manoeuvre MTB for applications in complex fluid environments, such as magnetic drug release systems and real-time tracking systems. Furthermore, this concept and methodology provide a paradigm for controlling the mobility of micro-/nanomotors based on natural small organisms.

Haitao Chen

Papers

Nanoparticle-Regulated Semiartificial Magnetotactic Bacteria with Tunable Magnetic Moment and Magnetic Sensitivity.