Enhanced photodynamic therapy: a review of combined energy sources

Photodynamic therapy (PDT) has been used in recent years as a non-invasive treatment for cancer, due to the side effects of traditional treatments such as surgery, radiotherapy, and chemother apy. This therapeutic technique requires a photosensitizer, light energy, and oxygen to produce reactive oxygen species (ROS) which mediate cellular toxicity. PDT is a useful non-invasive therapy for cancer treatment, but it has some limitations that need to be overcome, such as low-light-penetration depths, non-targeting photosensitizers, and tumor hypoxia. This review focuses on the latest innovative strategies based on the synergistic use of other energy sources, such as non-visible radiation of the electromagnetic spectrum (microwaves, infrared, and X-rays), ultrasound, and electric/magnetic fields, to overcome PDT limitations and enhance the therapeutic effect of PDT. The main principles, mechanisms, and crucial elements of PDT are also addressedThis work was supported by project MME reference 105399; CMEMS-UMinho Strategic Project UIDB/04436/2020 and UIDP/04436/2020; Infrastructures Micro&NanoFabs@PT, NORTE-01-0145-FEDER-022090, Portugal 2020; and MPhotonBiopsy, PTDC/FIS-OTI/1259/202