Fluorine End-Capped Optical Fibers for Photosensitizer Release and Singlet Oxygen Production

Abstract

The usefulness of a fiber optic technique for generating singlet oxygen and releasing the pheophorbide photosensitizer has been increased by the fluorination of the porous Vycor glass tip. Singlet oxygen emerges through the fiber tip with 669-nm light and oxygen, releasing the sensitizer molecules upon a [2 + 2] addition of singlet oxygen with the ethene spacer and scission of a dioxetane intermediate. Switching from a non-fluorinated to a fluorinated glass tip led to a clear reduction of the adsorbtive affinity of the departing sensitizer with improved release into homogeneous toluene solution and bovine tissue. But no difference was found in water since the sensitizer was insoluble. High surface coverage of the nonafluorohexylsilane enhanced the cleavage efficiency by 15% at the ethene site. The fluorosilane groups also caused crowding and seemed to reduce access of 1O2 to the ethene site, which attenuated the total quenching rate constant kT, although there was less wasted 1O2 (from surface physical quenching) at the fluorosilane-coated than the native SiOH silica. The observations support a quenching mechanism that the replacement of the SiOH groups for the fluorosilane C-H and C-F groups enhanced the 1O2 lifetime at the fiber tip interface due to less efficient electronic-to-vibronic energy transfer.

Photoactive Fluoropolymer Surfaces That Release Sensitizer Drug Molecules

“…This can be understood by the tendency of PEGylated compounds to adhere to surfaces with O−H groups. This result is similar with our recent work 48 where a pheophorbide sensitizer increased its adsorptive affinity for silica with higher quantities of O−H groups. The number of O−H bonds was important to tabulate because they can serve as adsorption sites.…”

“…48 Briefly, Vycor pieces were added to the nonafluorotrimethoxysilane in 0.07 wt/wt % in toluene and refluxed for 24 h under N 2 . Unreacted nonafluorotrimethoxysilane was washed off of the silica by Soxhlet extraction in methanol for 24 h. TriPEG chlorin 5 reacted with (3-iodopropyl)trimethoxysilane and was added to 0.33 g fluorinated silica 6 [shaped into pieces sized ∼5 mm × ∼8 mm ( d × l )] in refluxing toluene for 24 h to reach 7 .…”

“…48 Under subdued light, n -butanol solutions were presaturated with O 2 for 20 min and then illuminated with red light for 1.5 h, upon which 1 O 2 was generated and trapped by the alkene sites on the solid supports. These heterogeneous photolysis reactions contained 0.328 and 0.214 g of solids 7 and 10 , respectively.…”

Autocatalytic-Assisted Photorelease of a Sensitizer Drug Bound to a Silica Support

“…Scheme 1 shows a fluorinated silica surface [Vycor glass monolith coated with (CH 3 O) 3 SiCH 2 CH 2 CF 2 CF 2 CF 2 CF 3 = 1.6 mmol/g silica], 4 studied here that photoreleases the sensitizer, 4-formatebenzyl-pyropheophorbide ester (sensU, Scheme 1). The photorelease of sensU occurs by a reaction of singlet oxygen with the vinyl ether bond linking the pheophorbide to the silica with the subsequent scission of a dioxetane intermediate.…”

Synthesis and Characterization of Mono-, Di-, and Tri-Poly(ethylene glycol) Chlorin e6 Conjugates for the Photokilling of Human Ovarian Cancer Cells

“…(7) For 2 and 3 , the data pointed to a Type-II mechanism based on azide ion quenching, whereas for chlorin e 6 and 1 the situation is more complex where some contribution from a Type-I mechanism was evident. This brings us to our final point: because of our interest in fiber-based photosensitizer and singlet oxygen delivery methods, 40 desirable aspects of the tri-PEG chlorin conjugate, 3 , make it a potential sensitizer for incorporation into a fiber optic device, particularly for the area of ovarian cancer photodynamic therapy.…”