| Abstract | Despite recent advances in surgery, chemotherapy, and radiation treatment, survival of patients with advanced malignancy remains suboptimal. Photodynamic therapy is a relatively new cytotoxic treatment, predominantly used in anti-cancer approaches, that
depends on the retention of photosensitizers in tumor and their activation after light exposure in the presence of molecular oxygen. Photosensitizers are photo-sensible compounds that upon photoactivation, effect strongly localized oxidative damage within the target cells. The ability to confine activation of the photosensitizer by restricting illumination to the tumor allows for a certain degree of selectivity. Nevertheless, the targeted delivery of photosensitizers to defined cells is a major challenge in photodynamic therapy of cancer, and one area of importance is photosensitizer targeting. In this sense, an arsenal of targeting strategies has been developed recently. Alterations or increased levels in receptor expression of specific cellular type occur in the diseased tissues. Therefore, photosensitizers can be covalently attached to molecules such as specific peptides, leading to a receptor-mediated targeting strategy. These active targeting approaches may be particularly useful for vascular-targeted photodynamic therapy. The present chapter will focus on recent and significant advances and developments in targeting strategies in photodynamic therapy with the emphasis on target specificity. |
