title: The use of magnetic field effects on photosensitizer luminescence as a novel probe for optical monitoring of oxygen in photodynamic therapy.
abstract: The effect of a magnetic field on the steady-state and time-resolved optical emission of a custom fullerene-linked photosensitizer (PS) in liposome cell phantoms was studied at various oxygen concentrations (0.19-190 microM). Zeeman splitting of the triplet state and hyperfine coupling, which control intersystem crossing between singlet and triplet states, are altered in the presence of low magnetic fields (B < 320 mT), perturbing the luminescence intensity and lifetime as compared to the triplet state at B = 0. Measurements of the luminescence intensity and lifetime were performed using a time-domain apparatus integrated with a magnet. We propose that by probing magnet-affected optical emissions, one can monitor the state of oxygenation throughout the course of photodynamic therapy. Since the magnetic field effect (MFE) operates primarily by affecting the radical ion pairs related to type I photodynamic action, the enhancement or suppression of the MFE can be used as a measure of the dynamic equilibrium between the type I and II photodynamic pathways. The unique photo-initiated charge-transfer properties of the PS used in this study allow it to serve as both cytotoxic agent and oxygen probe that can provide in situ dosimetric information at close to real time.
authors.affiliation: Biophotonics Group, INO, 2740, Einstein St, Québec, QC, G1P 4S4, Canada. ozzy.mermut@ino.ca
authors.forename: O
authors.initials: O
authors.lastname: Mermut
authors.forename: K R
authors.initials: KR
authors.lastname: Diamond
authors.forename: J-F
authors.initials: JF
authors.lastname: Cormier
authors.forename: P
authors.initials: P
authors.lastname: Gallant
authors.forename: N
authors.initials: N
authors.lastname: Hô
authors.forename: S
authors.initials: S
authors.lastname: Leclair
authors.forename: J-S
authors.initials: JS
authors.lastname: Marois
authors.forename: I
authors.initials: I
authors.lastname: Noiseux
authors.forename: J-F
authors.initials: JF
authors.lastname: Morin
authors.forename: M S
authors.initials: MS
authors.lastname: Patterson
authors.forename: M L
authors.initials: ML
authors.lastname: Vernon
mesh_terms: D037741:Fullerenes / Q000737:chemistry; D049408:Luminescent Agents / Q000138:chemical synthesis / Q000737:chemistry*; D008280:Magnetics; D010100:Oxygen / Q000032:analysis*; D019047:Phantoms, Imaging; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000138:chemical synthesis / Q000737:chemistry*; D013997:Time Factors
chemical_list: D037741:Fullerenes; D049408:Luminescent Agents; D017319:Photosensitizing Agents; D010100:Oxygen