Hybrid fiber-optic device for spatiotemporal control of photosensitizer release and singlet oxygen delivery

This thesis outlined the gradual progress towards the development of the first fiber-optic singlet-oxygen generator designed for releasing singlet oxygen locally, which can surmount the challenges associated with current photodynamic therapy and water disinfection.;We developed a photochemical approach to clean generation of singlet oxygen in aqueous solution with a sensitizer (meso-tetra(N-methyl-4 pyridyl)porphine) adsorbed onto solid porous Vycor glass (PVG)]. Photophysical analysis revealed that oxygen collision onto the sensitizer adsorbed porous Vycor glass matrix converts ground-state oxygen into singlet oxygen ( 1O2) which diffuses into bulk aqueous solution. Singlet oxygen was detected in water by time-resolved methods and by chemical trapping with alkene, N-benzoyl methionine, and anthracene derivative to give hydroperoxide, N-benzoyl sulfoxide, and anthracene endoperoxide derivative. Based on this study, we developed a device that channels light and oxygen through a hollow core fiber optic into the sensitizer adsorbed Vycor glass which acts as a cap. Singlet oxygen was generated on a microscale at the fiber cap site selectively which then diffused out into the surrounding aqueous solution. A complete Escherichia coli inactivation was observed in 2 h when the fiber cap was immersed in 0.1 mL aqueous samples of 0.1--4.4 x 107 cells.;The prototype device was further modified to enhance singlet oxygen diffusion in aqueous solution as singlet oxygen has lifetime's ranges from microseconds to milliseconds and the corresponding diffusion distances of singlet oxygen ranges from nanometers to millimeters. Our efforts included 1O 2 generation by cleaving off sensitizer molecules away from the fiber optic probe to increase 1O2 formation at a distance from the probe tip. Synthetic methodology was developed to modify the glass probe to release photosensitizer molecules into the surrounding medium by an oxidative self-cleaving mechanism where 1O 2 was used as a sole reagent. We successfully attached pyropheophorbide photosensitizer containing a photosensitive electron rich alkene covalently to porous Vycor glass which is triggered for release on-site by visible light irradiation, via dioxetane decomposition to give two carbonyl fragments. The cleaved photosensitizer diffuses into solution to produce singlet oxygen at a distance from the glass surface which also improves the photooxidation efficiency of the heterogenous photosensitizer. Finally, a review of the literature on 'singlet oxygen as a reagent in organic synthesis' was accomplished, which represent the last chapter of the thesis.