title: The potential effectiveness of nanoparticles as radio sensitizers for radiotherapy.
abstract: BACKGROUND
  Application of nanoparticles as radio sensitizer is a promising field to improve efficiency of radiotherapy.
  
  
  METHODS
  This study was conducted to review nano radio sensitizers. PubMed, Ovid Medline, Science Direct, Scopus, ISI web of knowledge, and Springer databases were searched from 2000 to May 2013 to identify relevant studies. Search was restricted to English language.
  
  
  RESULTS
  We included any study that evaluated nanoparticles, volunteer of radio enhancement at radiotherapy on animals or cell lines. Nanoparticles can increase radio sensitivity of tumor cells. This effect was shown in vivo and in vitro, at kilovltage or megavoltage energies, in 24 reviewed studies. Focus of studies was on gold nanoparticles. Radio sensitizing effects of nanoparticles depend on nanoparticles' size, type, concentration, intracellular localization, used irradiation energy and tested cell line.
  
  
  CONCLUSIONS
  Literature suggests potency of nanoparticles for increasing cell radio sensitivity. Reviewed results are promising and warrant future clinical trials.
authors.affiliation: Department of Radiotherapy Oncology, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Babaei
authors.affiliation: Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Ganjalikhani
keywords: Gold nanoparticles; Nanoparticles; Radiation therapy; Radio sensitizer