title: Photosensitized breakage and damage of DNA by CdSe-ZnS quantum dots.
abstract: Strand breakages and nucleobase damages in plasmid DNA (pDNA) by CdSe-ZnS quantum dots (QDs) are investigated under different conditions of photoactivation. Here, streptavidin functionalized CdSe-ZnS QDs are conjugated to biotinylated pDNA, and photosensitized strand breakages and nucleobase damages in the conjugates are investigated using atomic force microscopy (AFM) imaging, gel electrophoreses analyses, and assay of reactive oxygen intermediates (ROI). Also, reactions of photoactivated pDNA-QD conjugates with base excision repair enzymes such as formamidopyrimidine glycosylase (Fpg) and endonuclease III (Endo III) show damages of purine and pyrimidine bases. The base excision repair enzymes recognize and remove the damaged bases. The base excision reactions of photoactivated pDNA-QD conjugates resulted in pDNA strand breakages, which appeared as sheared bands in agarose gel images. On the basis of AFM imaging, reactions of Fpg and Endo III with damaged pDNA, ROI assay, and literature reports, we attribute the breakage and damage of pDNA to its reactions with ROI. The production of ROI by photoactivated QDs is confirmed by nitroblue tetrazolium (NBT) assay. The current work shows that photoactivation of QD-conjugated nucleic acids for an extended period of time is not favorable for their stability. On the other hand, photoinduced production of ROI by QDs is an emerging research area with potential applications in the photodynamic therapy of cancer. In this regard, photosensitized damage of pDNA observed in the current work shows possibilities of QDs in nucleus-targeted photodynamic therapy.
authors.affiliation: Nanobioanalysis Team, Health Technology Research Center, National Institute of Advanced Industrial Science and Technology, 2217-14 Hayashi-cho, Takamatsu, Kagawa 761-0395, Japan.
authors.forename: AbdulAziz
authors.initials: A
authors.lastname: Anas
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Akita
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Harashima
authors.forename: Tamitake
authors.initials: T
authors.lastname: Itoh
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Vasudevanpillai
authors.initials: V
authors.lastname: Biju
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D004249:DNA Damage; D004587:Electrophoresis, Agar Gel; D018625:Microscopy, Atomic Force; D010777:Photochemistry; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; C058667:cadmium selenide; C031238:zinc sulfide