Photodynamic Therapy Using Gold Nanorods for Squamous Cell Carcinoma in Mice

Introduction: Photodynamic therapy for patients with esophageal cancer has been conducted as an alternative treatment. The general thermal treatment involves non-tumor-specific heating, and a good antitumor effect is not necessarily obtained. We sought to execute a method of tumor-specific heating by developing nanoparticles that accumulate in the tumor precisely to promote such heating. We herein report the antitumor effect of our newly developed photodynamic therapy using gold nanorods and near infrared light. Methods: Near infrared light exhibits high permeability in living tissues. Gold nanorods adjusted to 40 nm in long axis have low toxicity and are increased in temperature by irradiation with near infrared light displaying a wavelength of around 800 nm. In addition, based on the Enhanced Permeation and Retention Effect (EPR effect), approximately 100 nm particles may accumulate for tumor selectively. We developed gold nanorods placed into liposomes made of a lipid membrane of the size of about 100-200 nm diamiter to promote accumulation in tumor tissue and irradiated the rods with near infrared light to achieve tumor-specific heating. Results: We used tumor-bearing C3H/He mice treated with a squamous cell carcinoma cell line SCCVII 1*105. The mice were intravenously given liposomes containing gold nanorods and underwent photodynamic therapy using near infrared light irradiation 24 hours later. The temperature of the tumors significantly increased in the gold nanorod liposome group compared to that observed in the control group. Moreover the increase in tumor volume was inhibited in the group administered the nanorod liposomes. Conclusion: Gold nanorods strongly increase the efficacy of photodynamic therapy using near infrared light irradiation.