Ultrafast spectroscopy study of DNA photophysics after proflavine intercalation

Proflavine (PF), an acridine DNA intercalating agent, has been widespread applied as an anti-microbial and topical antiseptic agent due to its ability to suppress DNA replication. On the other hand, various studies show that PF intercalation to DNA can increase photogenotoxicity and has potential chances to induce carcinomas of skin appendages. However, the effects of PF intercalation on the photophysical and photochemical properties of DNA have not been sufficiently explored. In this study, the excited state dynamics of the PF intercalated d(GC)₉ • d(GC)₉ and d(AT)₉ • d(AT)₉ DNA duplex are investigated in an aqueous buffer solution. Under 267 nm excitation, we observed ultrafast charge transfer (CT) between PF and d(GC)₉ • d(GC)₉ duplex, generating a CT state with an order of magnitude longer lifetime compared to that of the intrinsic excited state reported for the d(GC)₉ • d(GC)₉ duplex. In contrast, no excited state interaction was detected between PF and d(AT)₉ • d(AT)₉. Nevertheless, a localized triplet state with a lifetime over 5 µs was identified in the PF-d(AT)₉ • d(AT)₉ duplex.