Supramolecular drug delivery platforms in photodynamic therapy

Photodynamic therapy (PDT) involves the photonic excitation of a photosensitizer (PS) dye in the presence of ambient oxygen, in turn forming reactive oxygen species that kill undesired cells. Many conventional PS possess organic frameworks that are hydrophobic and consequently prone to aggregation in solution which both alters photophysical characteristics of the dyes and prevents desired PS localization at target cells. Though chemical modification has traditionally been used to alter PS solubility and improve drug targeting, recently the prospect of using self-assembling supramolecular liposomal and nonliposomal delivery platforms has emerged as a method for drastically improving PS drug delivery. This chapter reviews liposomal dug delivery systems as well as nonliposomal systems including polymeric micelles, block copolymers, polymersomes, fullerosomes, nanocells, nanoemulsions, and lipoplexes. As PDT emerges as a viable clinical tool for the treatment of malignant as well as other diseases, modes of improving PS localization will become increasing relevant.