title: A hand-held fiber-optic implement for the site-specific delivery of photosensitizer and singlet oxygen.
abstract: We have constructed a fiber optic device that internally flows triplet oxygen and externally produces singlet oxygen, causing a reaction at the (Z)-1,2-dialkoxyethene spacer group, freeing a pheophorbide sensitizer upon the fragmentation of a reactive dioxetane intermediate. The device can be operated and sensitizer photorelease observed using absorption and fluorescence spectroscopy. We demonstrate the preference of sensitizer photorelease when the probe tip is in contact with octanol or lipophilic media. A first-order photocleavage rate constant of 1.13 h(-1) was measured in octanol where dye desorption was not accompanied by readsorption. When the probe tip contacts aqueous solution, the photorelease was inefficient because most of the dye adsorbed on the probe tip, even after the covalent ethene spacer bonds have been broken. The observed stability of the free sensitizer in lipophilic media is reasonable even though it is a pyropheophorbide-a derivative that carries a p-formylbenzylic alcohol substituent at the carboxylic acid group. In octanol or lipid systems, we found that the dye was not susceptible to hydrolysis to pyropheophorbide-a, otherwise a pH effect was observed in a binary methanol-water system (9:1) at pH below 2 or above 8.
authors.affiliation: Department of Chemistry and Graduate Center, City University of New York (CUNY), Brooklyn College, Brooklyn, NY, USA.
authors.forename: Adaickapillai
authors.initials: A
authors.lastname: Mahendran
authors.forename: Yasemin
authors.initials: Y
authors.lastname: Kopkalli
authors.forename: Goutam
authors.initials: G
authors.lastname: Ghosh
authors.forename: Ashwini
authors.initials: A
authors.lastname: Ghogare
authors.forename: Mihaela
authors.initials: M
authors.lastname: Minnis
authors.forename: Bonnie I
authors.initials: BI
authors.lastname: Kruft
authors.forename: Matibur
authors.initials: M
authors.lastname: Zamadar
authors.forename: David
authors.initials: D
authors.lastname: Aebisher
authors.forename: Lesley
authors.initials: L
authors.lastname: Davenport
authors.forename: Alexander
authors.initials: A
authors.lastname: Greer
mesh_terms: D002851:Chromatography, High Pressure Liquid; D005336:Fiber Optic Technology; D008081:Liposomes; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000008:administration & dosage*; D026082:Singlet Oxygen / Q000008:administration & dosage*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008081:Liposomes; D017319:Photosensitizing Agents; D026082:Singlet Oxygen