title: In vitro investigation of the biological effects associated with human dermal fibroblasts exposed to 2.52 THz radiation.
abstract: BACKGROUND
  Terahertz (THz) radiation sources are increasingly being used in military, defense, and medical applications. However, the biological effects associated with this type of radiation are not well characterized. In this study, we evaluated the cellular and molecular response of human dermal fibroblasts exposed to THz radiation.
  
  
  METHODS
  In vitro exposures were performed in a temperature-controlled chamber using a molecular gas THz laser (2.52 THz, 84.8 mW cm(-2), durations: 5, 10, 20, 40, or 80 minutes). Both computational and empirical dosimetric techniques were conducted using finite-difference time-domain (FDTD) modeling approaches, infrared cameras, and thermocouples. Cellular viability was assessed using conventional MTT assays. In addition, the transcriptional activation of protein and DNA sensing genes were evaluated using qPCR. Comparable analyses were also conducted for hyperthermic and genotoxic positive controls.
  
  
  RESULTS
  We found that cellular temperatures increased by 3°C during all THz exposures. We also found that for each exposure duration tested, the THz and hyperthermic exposure groups exhibited equivalent levels of cell survival (≥90%) and heat shock protein expression (∼3.5-fold increases). In addition, the expression of DNA sensing and repair genes was unchanged in both groups; however, appreciable increases were observed in the genotoxic controls.
  
  
  CONCLUSIONS
  Human dermal fibroblasts exhibit comparable cellular and molecular effects when exposed to THz radiation and hyperthermic stress. These findings suggest that radiation at 2.52 THz generates primarily thermal effects in mammalian cells. Therefore, we conclude that THz-induced bioeffects may be accurately predicted with conventional thermal damage models.
authors.affiliation: 711th Human Performance Wing, Radio Frequency Radiation Branch, Air Force Research Laboratory, Brooks City-Base, Texas, USA. gerald.wilmink@brooks.af.mil
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Wilmink
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Rivest
authors.forename: Caleb C
authors.initials: CC
authors.lastname: Roth
authors.forename: Bennett L
authors.initials: BL
authors.lastname: Ibey
authors.forename: Jason A
authors.initials: JA
authors.lastname: Payne
authors.forename: Luisiana X
authors.initials: LX
authors.lastname: Cundin
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Grundt
authors.forename: Xomalin
authors.initials: X
authors.lastname: Peralta
authors.forename: Dustin G
authors.initials: DG
authors.lastname: Mixon
authors.forename: William P
authors.initials: WP
authors.lastname: Roach
mesh_terms: D000328:Adult; D002470:Cell Survival / Q000528:radiation effects; D004249:DNA Damage; D020405:Dermis / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000528:radiation effects*; D006360:Heat-Shock Proteins / Q000096:biosynthesis; D006801:Humans; D006979:Hyperthermia, Induced / Q000009:adverse effects; D066298:In Vitro Techniques; D009152:Mutagenicity Tests; D016133:Polymerase Chain Reaction; D011874:Radiometry; D013696:Temperature; D055053:Terahertz Radiation / Q000009:adverse effects*
chemical_list: D006360:Heat-Shock Proteins