My talk will focus on fundamental and applied topics in the photosciences. First, a photoconversion of heptamethine cyanine to trimethine cyanine will be described that involves singlet oxygen and subsequent 2-carbon or 4-carbon truncations. The latter truncation appears to proceed through an allene hydroperoxide intermediate and then a downstream retro-Diels-Alder reaction for a potentially useful photobluing optical tool (∆lem of ~200 nm). Mechanistic details on this somewhat unusual cyanine phototruncation will be provided. Secondly, the development of a hand-held fiber device will be described which delivers singlet oxygen but not sensitizer by a superhydrophobic-tip. Red light emitted by the fiber tip is transmitted through the backside of a polydimethylsiloxane strip before irradiating a verteporfin coating facing a biofilm-covered tooth or gingival surface. The device shows promising results based on a Wistar rat model of periodontitis. Results will be highlighted from our collaborations with the groups of Martin J. Schnermann (National Cancer Institute), Alan Lyons (College of Staten Island), and Tayyaba Hasan (Harvard Medical School).