Photoreactive, water-soluble conjugates of hypericin with polyphosphazenes

The naturally occurring drug hypericin has invoked much interest in a wide variety of biomedical applications as an antiviral, antibacterial, or antitumor agent, as well as its use as a photosensitizer for photodynamic therapy. However, hypericin suffers from notoriously poor solubility, in particular in aqueous solution, a requirement for many biomedical applications. Using state-of-the-art living polymerization techniques, conjugates of hypericin with biodegradable polyphosphazenes were prepared which show significantly enhanced solubility in ethanol and water compared with the parent compound. Herein, we report the synthesis and structural characterization of these novel polymer-drug conjugates as well as initial testing of their photoreactivity.