title: Synergistic Cytotoxic Effect of Gold Nanoparticles and 5-Aminolevulinic Acid-Mediated Photodynamic Therapy against Skin Cancer Cells.
abstract: BACKGROUND
  Photodynamic therapy (PDT) is a promising therapeutic modality for the treatment of cancer and other diseases. In this study, the epidermoid carcinoma cell line A431 and the normal fibroblasts were used to investigate whether gold nanoparticles (GNPs) can induce an increase in cell death during PDT using 5-aminolevulinic acid (5-ALA) as a photosensitizer.
  
  
  METHODS
  Human fibroblast and A431 cells were grown in 96-well plates. The effect of GNPs on the efficacy of 5-ALA-mediated PDT (5-ALA-PDT) was evaluated by comparing the effect of 5-ALA with GNPs to the effect of 5-ALA alone. Cell viability was determined by the methyl- tetrazolium assay.
  
  
  RESULTS
  Dark toxicity experiments showed that 5-ALA at concentrations 0.5, 1 and 2 mM had no significant effect on cell viability of both cell lines. However, treatment of cells with 5-ALA (0.5 to 2 mM) and light dose of 25 Jcm(-2) led to 5-10% and 31-42% decrease in cell viability of fibroblast and A431 cells respectively. The data also shows that GNPs in both the absence and the presence of light, results in a dose-dependent decrease in cell viability of both cell lines. However, the sensitivity of cancer cells to GNPs at concentrations more than 24 μg/ml was approximately 2.5- to 4-fold greater than healthy cells. Furthermore, data indicates that 5-ALA in combination with GNPs results in a synergistic reduction in viability of A431 cells.
  
  
  CONCLUSIONS
  In summary, the findings of this study suggest that concomitant treatment with 5-ALA and GNPs may be useful in enhancing the effect of 5-ALA-PDT.
authors.affiliation: Biotechnology Center, Iranian Research Organization for Science and Technology, Tehran, Iran;
authors.forename: Mahnaz
authors.initials: M
authors.lastname: Hadizadeh
authors.affiliation: Medical Laser Research Center, Iranian Center for Medical lasers, Academic Center for Education, Culture and Research, Tehran, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Fateh
keywords: Aminolevulinic acid; Nanoparticles; Photochemotherapy