Abstract A molecular beacon-based platform that enables the switchable, DNA-structure-dependent generation of singlet oxygen ( 1O2) was designed. We prepared stem-and-loop structured oligodeoxynucleotides with an excellent photosensitizer, ruthenium complex, and cyclooctatetraene quencher attached at each strand end. The stem-and-loop structured oligodeoxynucleotides suppressed the photosensitized generation of 1O2 from the ruthenium photosensitizer owing to intramolecular quenching by the quencher located near the chromophore. Strikingly, hybridization with its complementary strand triggered a stem-and-loop to duplex transition that spatially separated the photosensitizer and quencher, thereby unleashing 1O2 generation upon photoirradiation. The duplex form showed strong cytotoxic effects owing to the efficient generation of 1O2. Thus, the structural change of DNA could regulate the generation of 1O2 and the following cytotoxic effects.
Harada et al. (Sun,) studied this question.