title: X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield.
abstract: Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 10(8) and (2.0 ± 0.1) × 10(9) singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 10(7)-2 × 10(9) singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality.
authors.affiliation: Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
authors.forename: Sandhya
authors.initials: S
authors.lastname: Clement
authors.affiliation: Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
authors.forename: Wei
authors.initials: W
authors.lastname: Deng
authors.affiliation: Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Camilleri
authors.affiliation: Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.|Department of Medical Biophysics, University of Toronto/University Health Network, Ontario, Canada.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Wilson
authors.affiliation: Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
authors.forename: Ewa M
authors.initials: EM
authors.lastname: Goldys
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage*; D026082:Singlet Oxygen / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D014965:X-Rays
chemical_list: D017319:Photosensitizing Agents; D026082:Singlet Oxygen
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