In this article the novel design of an anticancer drug delivery system is reported based on a pH-sensitive liposome retaining the Fe-porphyrin as a superoxide dismutase(SOD) mimic. The liposomes contained cationic/ anionic lipid combinations and were composed of Fe-porphyrin, L-α-phosphatidylcholine (DMPC), dimethylditetradecylammonium bromide (DTDAB), sodispdum oleate (OANa), and Tween-80. The size of the liposome was approximately 30 nm. The EC50 value (the effective concentration of compound required to produce a 50% lethal dose against cells) of the liposome was found to be significantly smaller than that of cisplatin as the control drug, suggesting that the liposome showed a high cytotoxicity toward the cancer cells. This is due to the fact that the pH-sensitive liposome rapidly corresponds to the acidic environments of the endosomes and is unstable, and the Fe-porphyrin is delivered into the cytosol. This result suggests that O2- may be useful as a target molecule to induce the selective death of cancer cells and that a pH-sensitive liposome retaining Fe-porphyrin as an SOD mimic is a new class of anticancer agent.
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