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 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 reduced the adsorbtive affinity of the departing sensitizer in homogeneous toluene solution and bovine tissue.  High surface coverage of the nonafluorohexylsilane favored the cleavage of the ethene site.   The fluorosilane groups caused crowding and seemed to reduce access of 1O2 to the ethene site, whereas non-fluorinated glass tended to physically quench 1O2 to a greater extent.  The observations support a quenching mechanism that the replacement of the fiber tip SiOH groups for C-H and C-F groups enhances the 1O2 lifetime due to reduced efficiency for electronic-to-vibronic energy transfer.

Fluorine end-capped optical fibers for photosensitizer drug delivery and singlet oxygen production

244th National Meeting (2012)

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