Dynamically Assembling Magnetic Nanochains as New Generation of Swarm‐Type Magneto‐Mechanical Nanorobots Affecting Biofilm Integrity

A swarm-type magneto-mechanical actuation strategy based on magnetic nanorobots aimed at combating methicillin-resistant bacteria that form biofilms is presented. These nanorobots can be propelled in a controlled and remote way by the exposure to a low-intensity and low-frequency rotating magnetic field. The nanorobots combine magnetic force-driven and torque-driven motions enabling multidirectional circulatory movements throughout the biofilm making bacteria accessible to antibiotic treatment.

Abstract

Bacterial resistance is gaining ground and novel, unconventional strategies are required to improve antibiotic treatments. As a synthetic analog of planktonic bacilli, the natural bacterial swimmers that can penetrate bacterial biofilms, ultra-short propelling magnetic nanochains are presented as bioinspired magnetic nanorobots, enhancing the antibiotic treatment in biofilm-forming Staphylococcus epidermidis. Propelling nanochains, activated by a low intensity (<20 mT) and low frequency (<10 Hz) rotating magnetic field (RMF), prompt the otherwise resistant biofilm-forming bacteria to become sensitive to methicillin, resulting in the killing of 99.99% of bacteria. While magnetic force-driven spherical magnetic nanoparticles were previously reported as unidirectional biofilm channel diggers, propelling nanochains emerge as second-generation magnetic nanorobots, which, due to their magnetic core, shape anisotropy, and negative zeta potential, combine magnetic responsiveness, torque-driven movement, and attractive electrostatic interactions to attach to bacterial aggregates and multi-directionally protrude throughout the biofilm, indulging mechanical forces. These synergistic effects, in combination with an antibiotic drug, destroy the bacterial extracellular matrix and eradicate the formed biofilm, as confirmed with several complementary techniques.