Optimized Heptamethine Cyanines for Photodynamic Therapy

Over 10 near-IR fluorescent sensitizers were prepared to explore their properties relevant to potential applications in photodynamic therapy (PDT). Key properties of these compounds are that they can be excited around 800 nm, (i) are hydrophilic, (ii) generate singlet oxygen with acceptable quantum yields, and (iii) are imported into cancer cells via the organic anion transporter proteins (OATPs). (This is crucial to tumor localization.) The N-substituents of these cyanines were varied to adjust their charges and polarities and to accommodate conjugation to other entities (e.g., biomolecules or fragments to expand their theranostic modalities). Thus, it was possible to optimize their photocytotoxicities without compromising their other desirable characteristics for PDT. Overall, sensitizers like this have superior characteristics relative to clinically approved sensitizers for PDT insofar as they can be excited at greater depths in tissue.