Water-Soluble Rotaxane-Type\nPorphyrin Dyes as a Highly\nMembrane-Permeable and Durable Photosensitizer Suitable for Photodynamic\nTherapy

Porphyrins have emerged as highly effective photosensitizers\nin\nthe field of photodynamic therapy (PDT) because of their high singlet\noxygen generation efficiency. However, most porphyrin derivatives\ndo not have adequate water solubility and cell membrane permeability\nsuitable for use in PDT. In addition, they frequently suffer from\nlow durability under photoirradiation. Here, we propose rotaxane-type\nphotosensitizers, in which a porphyrin axle is irreversibly encapsulated\nwithin cyclodextrins (CDs), to overcome the drawbacks of porphyrins\nfor PDT. The rotaxane-type photosensitizers were synthesized in high\nyields by employing a cooperative capture strategy. The CD derivatives\nworked as a transparent shell to impart a porphyrin axle not only\nwith water solubility but also with photostability. These rotaxanes\nshowed higher cell membrane permeability and photoinduced cytotoxic\nabilities than talaporfin sodium, presently used as a clinical photosensitizer.\nThe rotaxane-based photosensitizer could have potential for being\nideal PDT drugs.