Swarms of magnetic nanorobots to disrupt bacterial biofilms

Infections caused by bacteria organized in biofilms are very difficult to treat. In a study published in Advanced Healthcare Materials, scientists demonstrate that a new class of nanoparticles, magnetic nanochains, can disrupt biofilms with unprecedented efficiency. This disruption significantly enhances the action of antibiotics, paving the way for new prospects in the fight against bacterial resistance.

Bacterial biofilms: Structures that reinforce antibiotic resistance
Biofilms are communities of bacteria embedded within a protective layer known as the extracellular matrix. Composed of extracellular polymeric substances (polysaccharides, proteins, lipids, and DNA), this matrix acts as a physical and chemical barrier, making biofilms highly resistant to treatments and immune cells. These bacterial aggregates are involved in numerous chronic infections and contribute to the failure of antimicrobial therapies. Consequently, developing innovative, unconventional, and effective strategies to enhance antibiotic action—particularly by directly targeting the biofilm matrix—is crucial.

Mechanism of action of magnetic nanochains
To address this challenge, in a study published in Advanced Healthcare Materials, scientists present a solution based on the use of magnetic nanochains. Inspired by planktonic bacilli, these elongated structures consist of multiple superparamagnetic maghemite nanoparticles and possess unique properties that enable precise manipulation under magnetic fields. Specifically, they can be remotely controlled, form larger structures depending on the field intensity, generate localized rotating structures, and redisperse in the absence of the field.

These nanostructures can penetrate biofilms due to their shape, magnetic properties, and negative zeta potential—a surface characteristic that facilitates interactions with and infiltration into the biofilm’s protective matrix. Under the influence of a low-intensity, low-frequency rotating magnetic field, they can be activated in a controlled and multidirectional manner. They self-assemble into dynamic swarms, forming micro-bundles or micro-mats, which can exert mechanical forces within biofilms.

Figure: Bacterial biofilms prevent the penetration and action of antibiotics. By using magnetic nanochains, biofilms can be destabilized, allowing antibiotics to penetrate more effectively into the extracellular matrix and reach the bacteria. This significantly enhances their bactericidal effect, even at sub-inhibitory doses, reducing bacterial resistance and promoting bacterial elimination.

A combined treatment for maximum efficacy
By penetrating biofilms and exerting mechanical forces, magnetic nanochains disrupt the extracellular matrix but are not sufficient to kill the bacteria on their own. However, when combined with low doses of antibiotics (such as methicillin), magnetic nanochains can eliminate up to 99.99% of previously antibiotic-resistant bacteria. This mechanism relies on a combination of physical and chemical strategies, maximizing the bactericidal effect in the presence of the antibiotic while leaving bacteria unaffected in its absence. This synergy between the mechanical action of nanochains and the effect of antibiotics represents a significant breakthrough in treating resistant infections, particularly those involving Staphylococcus epidermidis biofilms.

Magnetic nanochains offer a promising solution to overcoming antibiotic resistance associated with biofilm formation. Their ability to penetrate and disrupt the protective structures of biofilms, combined with their controlled activation via a magnetic field, opens new avenues for developing more effective treatments. The potential applications of this technology are vast, ranging from the decontamination of medical devices to the management of chronic infections. Future research should focus on optimizing these nanostructures and integrating them into clinical protocols to maximize their impact on public health.

Reference

Kralj S, Da Silva C, Nemec S, et al. Dynamically Assembling Magnetic Nanochains as New Generation of Swarm-Type Magneto-Mechanical Nanorobots Affecting Biofilm Integrity. Adv Healthc Mater. Published online January 5, 2025. doi:10.1002/adhm.202403736

Contacts

CNRS Scientist | Jelena Kolosnjaj-Tabi | jelena.Kolosnjaj-tabi@ipbs.fr

Press | Françoise Viala | communication@ipbs.fr | 06 01 26 52 59

Swarms of magnetic nanorobots to disrupt bacterial biofilms