ABSTRACT
The selective, targeted delivery of photosensitizers to diseased cells is one of the major problems in photodynamic therapy (PDT) and is still a challenge to take up. One area of importance is the elaboration of targeted photosensitizers. Targeted therapy is a promising new therapeutic strategy, created to overcome growing problems of contemporary medicine, such as drug toxicity and drug resistance. An emerging modality of this approach is targeted PDT (TPDT) with the main aim of improving delivery of the photosensitizer to cancer tissue and, at the same time, enhancing specificity and efficiency of PDT. Depending on the mechanism of targeting, we can suggest dividing the strategies of TPDT into “passive,” “active,” and “activatable”; in the latter case, the photosensitizer is activated only in the targeted tissue. In this review, contemporary strategies of TPDT are described, including innovative new concepts, such as targeting assisted by peptides and aptamers, multifunctional nanoplatforms with navigation by magnetic field, or “photodynamic molecular beacons” activatable by enzymes and nucleic acid. The imperative of introducing a new paradigm of PDT, focused on the concepts of heterogeneity and dynamic state of tumor, is also called for.
