Employing high-frequency alternating magnetic fields for the non-invasive treatment of prosthetic joint infections

Abstract

Treatment of prosthetic joint infection (PJI) usually requires surgical replacement of the infected joint and weeks of antibiotic therapy, due to the formation of biofilm. We introduce a non-invasive method for thermal destruction of biofilm on metallic implants using high-frequency (>100 kHz) alternating magnetic fields (AMF). In vitro investigations demonstrate a >5-log reduction in bacterial counts after 5 minutes of AMF exposure. Confocal and scanning electron microscopy confirm removal of biofilm matrix components within 1 minute of AMF exposure, and combination studies of antibiotics and AMF demonstrate a 5-log increase in the sensitivity of Pseudomonas aeruginosa to ciprofloxacin. Finite element analysis (FEA) simulations demonstrate that intermittent AMF exposures can achieve uniform surface heating of a prosthetic knee joint. In vivo studies confirm thermal damage is confined to a localized region (<2 mm) around the implant, and safety can be achieved using acoustic monitoring for the presence of surface boiling. These initial studies support the hypothesis that AMF exposures can eradicate biofilm on metal implants, and may enhance the effectiveness of conventional antibiotics.

Temperature-sensitive liposomal ciprofloxacin for the treatment of biofilm on infected metal implants using alternating magnetic fields

“…This sample preparation protocol has been described previously for SEM imaging of biofilms [31]. The dried specimens were mounted on aluminum stubs, sputter coated with gold/palladium, and examined using the scanning electron microscope operating at 5kV (Zeiss ΣIGMA VP Field Emission Scanning Electron Microscope, Carl Zeiss Microscopy LTD, UK) [4]. …”

“…It was observed that a 4–5 log reduction in bacterial count (measured as colony forming units (CFU)) could be achieved within 5–7 minutes of heat treatment (20W of power) when Pseudomonas aeruginosa or Staphylococcus aureus biofilms were grown on metal washers [4]. This study also revealed a potential synergistic relationship between the antimicrobial ciprofloxacin and AMF exposures in the treatment of P. aeruginosa biofilms.…”

“…The rapidly increasing number of joint replacements that are projected due to population trends is expected to translate into hundreds of thousands of infected joints per year by 2030 [1]. The projected total annual cost to treat patients with PJIs in the United States in 2020 is about $1.6 billion [3, 4]. Multiple surgeries are usually required including replacement of the infected joint along with prolonged antibiotic administration, adding significant costs to the healthcare system [5].…”

“…Recently Coffel et al [19] described the possibility of using AMF exposures on implants coated with a ferromagnetic nanoparticle to generate heating to treat biofilms, although direct heating of metals may not need these coatings. In a recent study, we reported the safety of using AMF exposure to eradicate biofilm on a metal surface, methods to achieve uniform heating of a prosthetic joint, and in vivo methods to assess the extent of thermal damage to surrounding tissues after an AMF exposure [4]. …”

“…Our recent study also shows the successful treatment in vitro of Pseudomonas aeruginosa (PAO1) and Staphyloccocus aureus biofilms grown on metals using high-frequency alternating magnetic fields (AMF) [4]. It was observed that a 4–5 log reduction in bacterial count (measured as colony forming units (CFU)) could be achieved within 5–7 minutes of heat treatment (20W of power) when Pseudomonas aeruginosa or Staphylococcus aureus biofilms were grown on metal washers [4].…”