Cationic oligo-p-phenylene ethynylenes are very effective light-activated biocides and biosensors but degrade upon exposure to light. In this study, we explore the photochemistry of a class of "end-only" compounds from this series, which have cationic moieties on the ends of the backbone. Product characterization by mass spectrometry reveals that the photoreactivity of these molecules is higher than that of a previously studied oligomer and that the primary products of photolysis result from the addition of water or oxygen across the triple bond. In addition, a product suggesting the addition of peroxide or other reactive oxygen species across the triple bond was observed. To explore avenues by which the photodegradation of these compounds can be mitigated, the effects of complexation with sodium dodecyl sulfate micelles on their photochemistry was explored. Classical molecular dynamics simulations revealed that compounds that were protected from photolysis by SDS buried their phenylene ethynylene backbones into the interior of the micelle, protecting it from contact with water. This work has revealed a molecular basis for the protection of a novel class of light-activated biocides from irradiation that is consistent with the proposed photochemistry of these compounds. This information can be useful for developing photodegradation-resistant biocidal materials and applications for current compounds and leads to new molecular design.
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Article Synopsis
- Photodynamic therapy (PDT) is being studied as a treatment for neurodegenerative diseases like Alzheimer's by targeting toxic amyloid aggregates, although traditional methods face challenges with harmful off-target oxidation.
- A novel class of oligo--phenylene ethynylenes (OPEs) specifically binds and fluoresces in the presence of amyloid aggregates, demonstrating their ability to selectively generate singlet oxygen and photosensitize these aggregates under light.
- Compared to the conventional photosensitizer methylene blue, OPEs effectively oxidize amyloid fibrils without damaging surrounding cells, showcasing their potential as safer and more targeted theranostics in PDT for treating neurodegenerative disorders.
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