Photodynamic therapy (PDT) is an emerging cancer treatment that uses photosensitizers (PS), along with light to activate them, resulting in oxidation of various biological components in cancer tissues. However, since most potential PS are solubilized and given as aqueous solution, PS is non-specifically distributed in the body, leading to the induction of various side effects in normal tissues that are exposed to daylight such as skin and eyes. To overcome the problem associated with non-specific in vivo disposition of PS, various approaches have been applied to develop safer dosage forms for PS with more efficient tumor delivery and lower disposition to normal tissues. Passive drug targeting to tumors with nanoparticulate formulations has been recognized as one of the potentially useful approaches to improve the poor tissue specificity of conventional cancer chemotherapy and this approach should also be applicable for more efficient tumor delivery of PS. In this review article, several issues concerning the efficacy of PDT using nanoparticle-based formulations are discussed and our recent attempts to temporally enhance the vascular permeability within tumors with photodynamic treatment for the better therapeutic outcome of nanoparticle-based therapy are introduced.
Keywords: drug delivery; nanoparticle; photodynamic therapy (PDT); photosensitizer (PS); vascular permeability.