Breaking the Biofilm—Magnetic Nanoparticles for Cleaning Surfaces in Marine Environment

Marine biofilms, which are formed by the growth of various organisms, can significantly compromise underwater equipment especially for devices like sensors and camera lenses, by obscuring sensor readings and camera clarity. They can also escalate fuel consumption and corrosion on ships by altering hydrodynamics. These persistent biofilms necessitate costly removal and maintenance, posing a challenge to marine operations. Removing bacterial biofilms early on can prevent the attachment of harmful macro-organisms. This project proposes using magnetic nanoparticles (MNPs) to remove marine biofilms under alternating magnetic fields. Spherical iron oxide MNPs (diameter ~20 nm) were synthesized by the hydrothermal method, and their morphology, crystallinity, and magnetic properties were evaluated by electron microscopy, X-ray diffraction, and static and dynamic magnetometry. The synthesized MNPs have a polyethyleneimine coating, a positively charged polymer with antimicrobial properties. The integrity of these coatings was verified and quantified using Transmission Electron Microscopy (TEM), Z-potential measurements, Energy Dispersive X-ray Spectroscopy (EDS), and Electron Energy Loss Spectroscopy (EELS). The MNPs were internalized within lab grown <i>C. marina</i> biofilms and placed under alternating magnetic fields. Several high-frequency alternating magnetic fields, in the hundreds of kHz range were tested. This frequency range is designed to promote MNP heating for the MNP morphology and composition. Also, the MNPs were placed in a low-frequency magnetic field, which caused the particles to rotate due to their interaction with the magnetic field. This rotation generates mechanical torque that can disrupt the biofilm physically, augmenting the MNP’s ability to disturb and displace the biofilm matrix. The morphology of the biofilm and viability of the bacteria before and after alternating magnetic field treatment were evaluated by fluorescence microscopy and crystal violet absorbance. The study investigated the most effective MNP treatment regime and the effects of mechanical or thermal excitation on biofilm and bacterial physiology. The proposed research holds potential for providing a new and effective approach to addressing the problem of marine biofilms and could be used to treat biofilm caused by antibiotic-resistant bacteria strains.