4 - Sensitizers in photodynamic therapy

Abstract

Photodynamic therapy (PDT) is a treatment method, based on taking advantage of the reactive oxygen species generated by irradiation of photosensitizers (PSs). Among various classes of PSs, tetrapyrrole structures (porphyrins, chlorins, bacteriochlorins, and phthalocyanines) have been studied extensively, and many compounds have approved for clinical use. Other chemical structures such as synthetic dyes, squaraines, and transition metal complexes, and natural products such as hypericin, hypocrellin, riboflavin, and curcumin have also been investigated for their use in PDT. The effectiveness of the PDT is largely determined by PS localization at the desired tissue. To achieve the targeted delivery, PSs are being conjugated with biological molecules such as peptides, antibodies, proteins, and ligands that are complement to the target cell. The efficacy of PS is determined by a variety of parameters, including solubility, clearance, route of administration, retention period, stability, absorption wavelength, and biocompatibility. Each class of PSs has its own set of benefits and drawbacks, where the limitations are being addressed by the research community to provide the ideal PSs for PDT. This chapter primarily focuses on various classes of PSs that are being investigated in PDT. Further, it includes the applications of targeted PSs to achieve an effective PDT.