Abstract
Extending the application of photodynamic therapy (PDT) requires development of photosensitizers
(PSs) that can selectively accumulate within target tumors. Although researchers have developed various
kinds of PSs in recent years, only a few of them have reached the clinical development stage. This
article reviews the characteristics of clinically approved PSs to elucidate the physicochemical properties
which are necessary for their practical application and examines recent trends in the development of
drug delivery systems (DDSs) for PDT. In addition, this article introduces polymer-PS conjugates developed
in our lab which target acidic tumorous pH and the tumor-associated vasculature. Our polymer-
PS conjugates exhibited selective tumor accumulation after intravenous injection and a significantly
enhanced PDT effect in subcutaneous tumor models. Our DDSs also unveiled important fundamental
knowledge in photochemical damage to normal and tumor tissues, which may contribute to the future
design of DDSs for PDT.
