Photosensitizing agents that oxidatively cleave DNA are important to photodynamic therapy (PDT), an emerging treatment option for localized diseases that include early stage cancer. Most routinely used PDT agents require activation by a visible light source that emits at wavelengths less than 690 nm. However, the effective penetration depth of light through living tissue continues to increase as a function of increasing wavelength up to ~ 840 nm. While near-infrared excitation is highly desirable, so far DNA photo-cleavage above 800 nm has not been reported. The excited triplet state energies of many photosensitizers that absorb in this region are not high enough to efficiently generate reactive oxygen species. We have recently investigated the DNA interactions of symmetrical carbocyanine dyes in which two quinoline rings are joined by a central polymethine bridge that is <i>meso</i>-substituted with a hydrogen, chlorine, or bromine atom. In reactions containing halogenated dye, we report that irradiation at 808 nm and 830 nm sensitizes cleavage of plasmid DNA in good yields (pH 7.2 and 22 °C). Mechanisms underlying the photo-cleavage chemistry will be discussed.

DNA photo-cleavage by symmetrical quinoline carbocyanine dyes irradiated with near-infrared light

251st National Meeting (2016)

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