The bromoporphyrins as promising anti-tumor photosensitizers in vitro.

The synthesis of ideal photosensitizers (PSs) is considered to be the most significant bottleneck in photodynamic therapy (PDT). To discover novel PSs with excellent photodynamic anti-tumor activities, a series of novel photosensitizers 5,15-diaryl-10,20-dibromoporphyrins (I) were synthesized by a facile method. Compared with hematoporphyrin monomethyl ether (HMME) as the representative porphyrin-based photosensitizers, it is found that not only the longest absorption wavelength of all compounds was red-shifted to therapeutic window (660 nm) of photodynamic therapy, but also the singlet oxygen quantum yields were significantly increased. Furthermore, all compounds exhibited lower dark toxicity (except I) and stronger phototoxicity (except I) against Eca-109 tumor cells than HMME. Among them, I possessed the highest singlet oxygen quantum yield (Φ = 0.205), the lower dark toxicity and the strongest phototoxicity (IC = 3.5 μM) in vitro. The findings indicated the compounds I had the potential to become anti-tumor agents for PDT.