Methotrexate-loaded, photosensitized erythrocytes: a photo-activatable carrier/delivery system for use in cancer therapy.

With a view towards the design of a system incorporating both the use of chemotherapeutics and photodynamic therapy for use in cancer treatment modalities, erythrocytes have been loaded with methotrexate and subsequently photosensitized by exposure to hematoporphyrin derivative. Loading of methotrexate into erythrocytes has been optimized by examining variations in electroporation conditions. Maximum loading indices observed were in the region of 64%. In order to obtain rapid pre-defined release of chemotherapeutic from the system, the erythrocytes were photosensitized. Light-dependent release of methotrexate from the system was examined. In addition, studies measuring the cytotoxic effects of light-activated release from the system using Hela cells as a target, suggested that decreases in cell viability following exposure to light resulted from the combined effects of chemotherapy and photoradiation therapy. Potential applications and advantages associated with this novel system are discussed.