Activatable triplet photosensitizers: magic bullets for targeted photodynamic therapy
Abstract
Photodynamic therapy (PDT) is a promising minimally invasive therapeutic approach to activate oxidative photodamage and subsequent cell death of the targeted tumor. The classical non-targeted photosensitizers lack sufficient tumor selectivity and are taken up in the neighboring normal tissues, resulting in undesirable adverse effects. To overcome this obstacle, diverse tumor-targeting approaches have been developed, such as targeted photodynamic therapy (TPDT). In the present review we discuss recently emerged strategies in the designing of targeted photosensitizers for TPDT, including targeting the tumor specific enzyme, photodynamic molecular beacons, the PDT reagents that target the acidic microenvironment and that target the overexpressed folic acid receptors on the cancer cell surfaces. The approaches used in TPDT, such as passive or active and/or activatable are discussed. The molecular structure assembly and structure–function relationship in chemistry as well as from a biological approach are also highlighted.