Alternating Magnetic Fields Remove Biofilms but Damage Cells on Implant Models Also with Negligible Bulk Heating

Implant-associated infections caused by bacterial biofilms remain a major clinical challenge, with high morbidity, often necessitating prolonged antibiotic therapy or implant revision surgery. To address the need for noninvasive alternatives, we investigated the use of alternating magnetic fields (AMFs) as a localized treatment modality for eradicating Staphylococcus aureus biofilms on titanium implant model surfaces. We demonstrate that AMF exposure effectively removes biofilms and kills bacteria at moderately elevated temperatures on the implant. Importantly, our results demonstrate that the antimicrobial efficacy of AMF treatment is primarily not due to heating. AMF vastly outperforms pure heating to the same temperatures for biofilm removal, despite inductive heating being the generally proposed mechanism for AMF antimicrobial action. Based on complementary imaging methods, we provide evidence that mechanical disruption, not a pure thermal effect, potentially driven by cavitation phenomena induced by transient, localized high temperature gradients, removes bacterial biofilms from titanium surfaces during AMF exposure. However, this mechanism also compromises the integrity of adjacent mammalian cells; confluent layers of SaOS-2 osteoblast-like cells exhibited actin cytoskeleton disintegration, membrane perforation, and a loss of viability even after brief AMF exposures. Our findings highlight a dual effect of AMF treatment: efficient biofilm removal is accompanied by collateral cytotoxicity, which requires further mechanistic research for clinically safe and effective AMF-based infection management strategies.