title: Enhancement of the killing effect of low-temperature plasma on Streptococcus mutans by combined treatment with gold nanoparticles.
abstract: BACKGROUND
  Recently, non-thermal atmospheric pressure plasma sources have been used for biomedical applications such as sterilization, cancer treatment, blood coagulation, and wound healing. Gold nanoparticles (gNPs) have unique optical properties and are useful for biomedical applications. Although low-temperature plasma has been shown to be effective in killing oral bacteria on agar plates, its bactericidal effect is negligible on the tooth surface. Therefore, we used 30-nm gNPs to enhance the killing effect of low-temperature plasma on human teeth.
  
  
  RESULTS
  We tested the sterilizing effect of low-temperature plasma on Streptococcus mutans (S. mutans) strains. The survival rate was assessed by bacterial viability stains and colony-forming unit counts. Low-temperature plasma treatment alone was effective in killing S. mutans on slide glasses, as shown by the 5-log decrease in viability. However, plasma treatment of bacteria spotted onto tooth surface exhibited a 3-log reduction in viability. After gNPs were added to S. mutans, plasma treatment caused a 5-log reduction in viability, while gNPs alone did not show any bactericidal effect. The morphological changes in S. mutans caused by plasma treatment were examined by transmission electron microscopy, which showed that plasma treatment only perforated the cell walls, while the combination treatment with plasma and gold nanoparticles caused significant cell rupture, causing loss of intracellular components from many cells.
  
  
  CONCLUSIONS
  This study demonstrates that low-temperature plasma treatment is effective in killing S. mutans and that its killing effect is further enhanced when used in combination with gNPs.
authors.forename: Sang Rye
authors.initials: SR
authors.lastname: Park
authors.forename: Hyun Wook
authors.initials: HW
authors.lastname: Lee
authors.forename: Jin Woo
authors.initials: JW
authors.lastname: Hong
authors.forename: Hae June
authors.initials: HJ
authors.lastname: Lee
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Byul Bo-Ra
authors.initials: BB
authors.lastname: Choi
authors.forename: Gyoo Cheon
authors.initials: GC
authors.lastname: Kim
authors.forename: Young Chan
authors.initials: YC
authors.lastname: Jeon
mesh_terms: D015169:Colony Count, Microbial; D006046:Gold / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry*; D050296:Microbial Viability / Q000187:drug effects*; D008963:Molar / Q000382:microbiology*; D058626:Plasma Gases / Q000737:chemistry / Q000494:pharmacology*; D013295:Streptococcus mutans / Q000187:drug effects*; D013696:Temperature
chemical_list: D058626:Plasma Gases; D006046:Gold
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