Researchers create magnetic microrobots to remove biofilms

The new technology uses iron oxide nanoparticle robots with a dual catalytic-magnetic mechanism to break down matrix, kill bacteria and remove the debris

Magnetically-driven robots designed to precisely, efficiently, and controllably kill, degrade, and remove biofilms have been created at the University of Pennsylvania. A group of engineers, dentists and biologists have teamed up to create the microscopic solution to the harmful buildup.

Biofilms are hardy, firmly attached structures of microorganisms that can lead to drug-resistant infection and surface destruction. Their problematic existence, and specifically how to remove them, is the subject of much research and innovation.

The inter-disciplinary team formed as a result of pure chance that saw them discover they were working on congruent projects. Together, with the knowledge and experience from their hugely diverse backgrounds, the team designed the catalytic antimicrobial robots (CARs).

Mechanism

The robots are iron oxide nanoparticles (NPs) moulded into helicoid shapes that use dual catalytic-magnetic functionality to attack the structure on a multitude of fronts.

Firstly they generate bactericidal free radicals, this in turn, breaks down the biofilm exopolysaccharide (EPS) matrix, and finally removes the fragmented biofilm debris via magnetic field–driven robotic assemblies.

Biofilms grow in so many places that the implications of a removal method could have an impact on many industries.

The compelling factor in this approach is that the robots not only degrade the matrix and kill the bacteria, but also physically remove the debris. This removal decreases the chance of the film growing back.

Hyun (Michel) Koo, lead research of the uPenn team, said: "These robots can do all three at once very effectively, leaving no trace of biofilm whatsoever."

Microrobots clear a glass plate of a biofilm in this time-lapse image
Credit: Geelsu Hwang and Edward Steager/University of Pennsylvania

Robot breeds

Two distinct CAR platforms were developed during the study. The biohybrid CAR platform was formed from NPs and biofilm degradation products. After catalytic bacterial killing and EPS disruption, magnetic field gradients assembled NPs and the biodegraded products into a plow-like superstructure. When driven with an external magnetic field, the biohybrid CAR completely removed biomass in a controlled manner, preventing biofilm regrowth. Biohybrid CARs could be swept over broad swathes of surface or moved over well-defined paths for localised removal with microscale precision.

Alternatively, the 3D-moulded CAR platform is a polymeric soft robot with embedded catalytic-magnetic NPs, formed in a customised 3D-printed mould to perform specific tasks in enclosed domains. Vane-shaped CARs remove biofilms from curved walls of cylindrical tubes, and helicoid-shaped CARs drill through biofilm clogs while simultaneously killing bacteria.

The real world

The next step for this technology would be to clinical applications. In this, the researchers have the support of the Penn Center for Health, Devices and Technology. Due to the background of the researchers in the study, the primary focus of this is within the dental field. However, the team has also expressed hope that it could be used in reducing the risk of contamination of implants and keeping water pipes and catheters clean.

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