Nanosecond pulsed plasmas for biomedical disinfection

Summary form only given. Non-equilibrium atmospheric-pressure plasma has emerged as a novel technology for biomedical and environmental applications. We present here the generation of 100 ns-pulsed, atmospheric-pressure, 2-3 cm long, pencil or needle-like plasma plumes, and their applications in root canal and wound disinfections. Well-established bacterial biofilms derived from saliva and inoculated into root canals were disinfected after 5-minute treatment with a 2-3 mm diameter plasma plume. Scanning electron microscopy (SEM) shows complete destruction of endodontic biofilms for a depth of 1 mm inside the root canal. A recently-developed plasma dental needle (~1 mm in diameter) is able to extend into the entire root canal of an instrumented human tooth, indicating the promising clinical potential in application of the room temperature plasmas for endodontic disinfection. In addition, effective inactivation of typical wound bacteria, Staphylococcus aureus, Pseudomonas aeruginosa, and Staphylococcus epidermidis on nutrient agar plates was observed after treatment with the plasma needle for 5 minutes and incubation for 24 hours. The bacteria-free (>99%) voids on agar plate created by plasma exposure are larger than 3 cm in diameter for an initial bacterial concentration of >105 CFUs/cm2, which implies that the nanosecond pulsed plasma needle can also be an efficient, effective, and safe wound disinfection tool. Possible plasma bactericidal mechanisms including oxidation with reactive chemical species (O, 03, OH, etc.), surface detachment, electrostatic disruption, and UV radiation are discussed.