Diverse applications of nanoparticles (NPs) have revolutionized various sectors in society. In the recent decade, particularly magnetic nanoparticles (MNPs) have gained enormous interest owing to their applications in specialized areas such as medicine, cancer theranostics, biosensing, catalysis, agriculture, and the environment. Controlled surface engineering for the design of multi-functional MNPs is vital for achieving desired application. The MNPs have demonstrated great efficacy as thermoelectric materials, imaging agents, drug delivery vehicles, and biosensors. In the present review, first we have briefly discussed main synthetic methods of MNPs, followed by their characterizations and composition. Then we have discussed the potential applications of MNPs in different with representative examples. At the end, we gave an overview on the current challenges and future prospects of MNPs. This comprehensive review not only provides the mechanistic insight into the synthesis, functionalization, and application of MNPs but also outlines the limits and potential prospects.

/pdf/review-on-recent-progress-in-magnetic-nanoparticles-us9xjjzwxz.pdf

Review on Recent Progress in Magnetic Nanoparticles: Synthesis, Characterization, and Diverse Applications

Magnetic helical micro-/nanomachines: Recent progress and perspective

Biofilm eradication from medical implants is of fundamental importance, and the treatment of biofilm‐associated pathogen infections on inaccessible biliary stents remains challenging. Magnetically driven microrobots with controlled motility, accessibility to the tiny lumen, and swarm enhancement effects can physically disrupt the deleterious biostructures while not developing drug resistance. Magnetic urchin‐like capsule robots (MUCRs) loaded with magnetic liquid metal droplets (MLMDs, antibacterial agents) are designed using natural sunflower pollen, and the therapeutic effect of swarming MUCR@MLMDs is explored for eradicating complex mixtures of bacterial biofilm within biliary stents collected from patients. The external magnetic field triggers the emergence of the microswarm and induces MLMDs to transform their shape into spheroids and rods with sharp edges. The inherent natural microspikes of MUCRs and the obtained sharp edges of MLMDs actively rupture the dense biological matrix and multiple species of embedded bacterial cells by exerting mechanical force, finally achieving synergistic biofilm eradication. The microswarm is precisely and rapidly deployed into the biliary stent via endoscopy in 10 min. Notably, fluoroscopy imaging is used to track and navigate the locomotion of microswarm in biliary stents in real‐time. The microswarm has great potential for treating bacterial biofilm infections associated with medical implants.

Magnetic Microswarm and Fluoroscopy‐Guided Platform for Biofilm Eradication in Biliary Stents

Urinary-based infections affect millions of people worldwide. Such bacterial infections are mainly caused by Escherichia coli (E. coli) biofilm formation in the bladder and/or urinary catheters. Herein, the authors present a hybrid enzyme/photocatalytic microrobot, based on urease-immobilized TiO2 /CdS nanotube bundles, that can swim in urea as a biocompatible fuel and respond to visible light. Upon illumination for 2 h, these microrobots are able to remove almost 90% of bacterial biofilm, due to the generation of reactive radicals, while bare TiO2 /CdS photocatalysts (non-motile) or urease-coated microrobots in the dark do not show any toxic effect. These results indicate a synergistic effect between the self-propulsion provided by the enzyme and the photocatalytic activity induced under light stimuli. This work provides a photo-biocatalytic approach for the design of efficient light-driven microrobots with promising applications in microbiology and biomedicine.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/smll.202106612

Enzyme-Photocatalyst Tandem Microrobot Powered by Urea for Escherichia coli Biofilm Eradication.

Multi-stimuli-response programmable soft actuators with site-specific and anisotropic deformation behavior

Biofilm is difficult to thoroughly cure with conventional antibiotics due to the high mechanical stability and antimicrobial barrier resulting from extracellular polymeric substances. Encouraged by the great potential of magnetic micro-/nanorobots in various fields and their enhanced action in swarm form, we designed a magnetic microswarm consisting of porous Fe3O4 mesoparticles (p-Fe3O4 MPs) and explored its application in biofilm disruption. Here, the p-Fe3O4 MPs microswarm (p-Fe3O4 swarm) was generated and actuated by a simple rotating magnetic field, which exhibited the capability of remote actuation, high cargo capacity, and strong localized convections. Notably, the p-Fe3O4 swarm could eliminate biofilms with high efficiency due to synergistic effects of chemical and physical processes: (i) generating bactericidal free radicals (•OH) for killing bacteria cells and degrading the biofilm by p-Fe3O4 MPs; (ii) physically disrupting the biofilm and promoting •OH penetration deep into biofilms by the swarm motion. As a demonstration of targeted treatment, the p-Fe3O4 swarm could be actuated to clear the biofilm along the geometrical route on a 2D surface and sweep away biofilm clogs in a 3D U-shaped tube. This designed microswarm platform holds great potential in treating biofilm occlusions particularly inside the tiny and tortuous cavities of medical and industrial settings.

Magnetic Microswarm Composed of Porous Nanocatalysts for Targeted Elimination of Biofilm Occlusion

Occlusion of the T-tube (tympanostomy tube) is a common postoperative sequela related to bacterial biofilms. Confronting biofilm-related infections of T-tubes, maneuverable and effective treatments are still challenging presently. Here, we propose an endoscopy-assisted treatment procedure based on the wobbling Fe2O3 helical micromachine (HMM) with peroxidase-mimicking activity. Different from the ideal corkscrew motion, the Fe2O3 HMM applies a wobbling motion in the tube, inducing stronger mechanical force and fluid convections, which not only damages the biofilm occlusion into debris quickly but also enhances the catalytic generation and diffusion of reactive oxygen species (ROS) for killing bacteria cells. Moreover, the treatment procedure, which integrated the delivery, actuation, and retrieval of Fe2O3 HMM, was validated in the T-tube implanted in a human cadaver ex vivo. It enables the visual operation with ease and is gentle to the tympanic membrane and ossicles, which is promising in the clinical application.

Endoscope-assisted magnetic helical micromachine delivery for biofilm eradication in tympanostomy tube

Electrical stimulation is a promising method to modulate gastrointestinal disorders. However, conventional stimulators need invasive implantation and removal surgeries associated with risks of infection and secondary injuries. Here, we report a battery-free and deformable electronic esophageal stent for wireless stimulation of the lower esophageal sphincter in a noninvasive fashion. The stent consists of an elastic receiver antenna infilled with liquid metal (eutectic gallium-indium), a superelastic nitinol stent skeleton, and a stretchable pulse generator that jointly enables 150% axial elongation and 50% radial compression for transoral delivery through the narrow esophagus. The compliant stent adaptive to the dynamic environment of the esophagus can wirelessly harvest energy through deep tissue. Continuous electrical stimulations delivered by the stent in vivo using pig models significantly increase the pressure of the lower esophageal sphincter. The electronic stent provides a noninvasive platform for bioelectronic therapies in the gastrointestinal tract without the need for open surgery.

https://www.science.org/doi/pdf/10.1126/sciadv.ade8622?download=true

Wirelessly powered deformable electronic stent for noninvasive electrical stimulation of lower esophageal sphincter

Bacterial biofilms are widely found in nature, and they can be a major factor in many local chronic infections inside the human body. To date, effective elimination of biofilms is intractable for conventional antibiotic therapies due to the existence of bacteria-protecting extracellular polymeric substances. For biofilm eradication in tiny tubular structures, magnetic hydrogel micromachines (MHM) are designed that are capable of performing mechanical disruption of biofilms while releasing antibacterial agents in a controllable fashion. Two modes of motion controlled by external magnetic fields, namely planar rotation and wobbling modes, have been investigated to drive the micromachines to interact and destruct biofilms. In addition, the presented micromachines are composed of thermosensitive PNIPAm hydrogel that can load with the antibacterial agent (H2O2) and release them upon heating. The Fe3O4 nanoparticles embedded in the hydrogel matrix act as catalysts for the Fenton reaction, generating bacteria-killing free radicals. The synergetic biofilm elimination effect has been experimentally demonstrated in well plates and small tubes. The presented MHMs may provide a new design to treat biofilm-related infections in narrow and confined spaces. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/aisy.202300092

Zifeng Zhang

Papers

Magnetic Microswarm Composed of Porous Nanocatalysts for Targeted Elimination of Biofilm Occlusion

Magnetic Microswarm and Fluoroscopy‐Guided Platform for Biofilm Eradication in Biliary Stents

Endoscope-assisted magnetic helical micromachine delivery for biofilm eradication in tympanostomy tube

Wirelessly powered deformable electronic stent for noninvasive electrical stimulation of lower esophageal sphincter

Magnetic Hydrogel Micromachines with Active Release of Antibacterial Agent for Biofilm Eradication