Combination of Photodynamic Therapy and Nanotechnology: Non-Invasive Weapon Against Cancer

摘要

Cancer has been reported as the second leading cause of death in the United States. Photodynamic therapy (PDT) has been introduced for clinical approaches as a non-invasive treatment and effective modality to selectively destroy cancers. It was more than 100 years ago when scientists noticed about the toxicity of combined light and some specific drugs which may result in cell death. In PDT, cancer destruction relies on applying a photosensitizing (PS) drug followed by light. Absorbed light can activate PS to transfer energy to existing molecules and substrates or oxygen to generate reactive oxygen species (ROS) and singlet oxygen. These products are highly toxic to cells and are able to damage or kill cancer cells. It is believed that singlet oxygen cannot damage cells far from the exposed area by light due to its high reactivity, short half-life (<0.04 /as), and short distance diffusion (<0.02 μm). High tumor selectivity, low systemic toxicity, low possibility of secondary effects, possibility of inducing the repeatable cycles of treatments as well as the possibility for combination with other therapies such as radiotherapy and chemotherapy are the advantages of PDT over other treatments. All of the adverse effects of PDT have been limited to photosensitivity reaction and swelling in the treated area which may cause pain or trouble swallowing or breathing. Here we review the history, mechanisms, potential challenges and alternative solutions for practical applications of PDT on cancer treatment.