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Photodynamic Therapy

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Photodynamic therapy (PDT) is a form of phototherapy that consists of 3 main components; photosensitizers (light sensitive molecules), light and oxygen. Currently, PDT is being used as a treatment modality for a variety of specific tumours, skin diseases, and precancerous and non-cancerous diseases . The minimally invasive and localised treatment utilize components that are non-toxic when used independently. The effects of PDT include damage to tumour vasculature, direct killing of tumour cells via cytotoxic activity, and inducing an antitumor reaction. When the photosensitizers are administered, there is a preferential uptake of photosensitizers by malignant tissues in the immediate locale than normal cells in the same region ). These photosensitizers …show more content…

Type I reaction results in the formation of free radicals in which then reacts with oxygen to rapidly produce highly reactive oxygen species. Type II photoreaction involves the transfer of photosensitizer energy excess straight to triplet oxygen creating singlet oxygen. While the highly reactive oxygen species from Type I photoreaction attack cellular targets, the singlet oxygen from Type II has seen to induce PDT-mediated cell damage. During illumination with light of a specific wavelength, the photosensitizers contained in mitochondria may induce apoptosis whereas photosensitizers in lysosomes and cell membranes may cause necrosis. There are several factors that determine the efficacy of PDT. This includes the type and dose of photosensitizer used, time between administration of photosensitizer and light irradiation, total light dose and its fluorance rate, tumour oxygen concentration and possibly, other poorly recognise

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