Photosensitizers in photodynamic therapy: An advancement in cancer treatment

Photodynamic therapy (PDT) is a clinically proven advancement in cancer treatment that has progressively gained consideration as a possible method of cancer treatment over time. This therapy, which involves the administration of a photosensitizing drug before activation of the drug with light from a source such as a laser to produce a cytotoxic effect, is minimally invasive and could increase the life expectancy of cancer patients. Cancer has been a major threat to human health, and it affects the quality of life of cancer patients as it is one of the topmost causes of mortality worldwide. The burden of cancer has been projected to increase to 2.1 million new cases and 1.4 million deaths in Africa by 2040. It is therefore expedient to put in more effort in proffering preventive measures, more efficient treatments, and possible cures for this disease. Recent studies have shown that many types of tumors can be destroyed using PDT. Tumor cells are destroyed via apoptosis, necrosis, and autophagy through some mechanisms in PDT. The successful outcome of this therapy depends greatly on three components which are photosensitizer (PS), light and molecular oxygen. Out of these three, photosensitizer is the most essential. Among the characteristics of a potent PS are the presence of a tetrapyrrole structure and the ability to initiate a photodynamic reaction when irradiated typically at a wavelength between 600 nm and 800 nm, although some PS can function effectively outside this range. This review highlights the effectiveness of PDT in the treatment of cancer and emphasizes the importance of PS, with more focus on those derived from natural sources, in determining the outcome of the therapy.