title: Single cell responses to spatially controlled photosensitized production of extracellular singlet oxygen.
abstract: The response of individual HeLa cells to extracellularly produced singlet oxygen was examined. The spatial domain of singlet oxygen production was controlled using the combination of a membrane-impermeable Pd porphyrin-dendrimer, which served as a photosensitizer, and a focused laser, which served to localize the sensitized production of singlet oxygen. Cells in close proximity to the domain of singlet oxygen production showed morphological changes commonly associated with necrotic cell death. The elapsed postirradiation "waiting period" before necrosis became apparent depended on: (1) the distance between the cell membrane and the domain irradiated, (2) the incident laser fluence and, as such, the initial concentration of singlet oxygen produced and (3) the lifetime of singlet oxygen. The data imply that singlet oxygen plays a key role in this process of light-induced cell death. The approach of using extracellularly generated singlet oxygen to induce cell death can provide a solution to a problem that often limits mechanistic studies of intracellularly photosensitized cell death: it can be difficult to quantify the effective light dose, and hence singlet oxygen concentration, when using an intracellular photosensitizer.
authors.affiliation: Department of Chemistry, Center for Oxygen Microscopy and Imaging, Aarhus University, Århus, Denmark.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Pedersen
authors.forename: Louise E
authors.initials: LE
authors.lastname: Sinks
authors.forename: Thomas
authors.initials: T
authors.lastname: Breitenbach
authors.forename: Nickolass B
authors.initials: NB
authors.lastname: Schack
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Vinogradov
authors.forename: Peter R
authors.initials: PR
authors.lastname: Ogilby
mesh_terms: D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D002462:Cell Membrane / Q000187:drug effects / Q000528:radiation effects; D005110:Extracellular Space; D005260:Female; D006367:HeLa Cells; D006801:Humans; D007834:Lasers; D008652:Mesoporphyrins / Q000494:pharmacology*; D008665:Metalloporphyrins / Q000494:pharmacology*; D008853:Microscopy; D010778:Photochemotherapy / Q000379:methods; D017319:Photosensitizing Agents / Q000494:pharmacology*; D059010:Single-Cell Analysis / Q000295:instrumentation / Q000379:methods; D026082:Singlet Oxygen / Q000009:adverse effects* / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D008652:Mesoporphyrins; D008665:Metalloporphyrins; D017319:Photosensitizing Agents; C079625:palladium-meso-tetra(4-carboxyphenyl)porphine; D026082:Singlet Oxygen