photodynamic therapy abbr., PDT otherwise photoradiation therapy; phototherapy; photochemotherapy (rus. терапия, фотодинамическая abbr., ФДТ) — a method to eliminate diseased cells in the body by accumulating the substance inside the cells, e.g. a photosensitizer or metallised nanoparticles, which destruct the cells from the inside when exposed to radiation of a certain wavelength through generating reactive oxygen species or hyperthemia.

Description

Photodynamic therapy (PDT) was first proposed for cancer treatment more than 100 years ago. It is currently used to treat cancer, eye and skin disorders. Photosensitizers are compounds based on protoporphyrin IX, phthalocyanines or their precursors that absorb light efficiently Photosensitizers are administered intravenously or locally applied onto the skin or mucous membranes. PDT methods and procedures using silicon nanoparticles coated with gold atom nanofilms (nanoshells) are being developed. Photosensitizers accumulate in tumour due to the high permeability of tumour blood vessels and high metabolic activity of tumour cells. Targeted delivery of chemical photosensitizers based on their specific interaction with diseased cells, are not yet well developed. Currently, lasers are used as light sources with the radiation in the red visible spectrum with a wavelength corresponding to the absorption maximum of the photosensitizer. When the light energy is absorbed, excited photosensitizer molecules react with surrounding oxygen molecules, generating singlet oxygen and destroying the cells by oxidative damage. When gold nanoparticles are used, the cells die because of excessive heating. The PDT has a limitation in use since the visible light can not penetrate through more than 1 cm of tissue, thus this therapy is mainly aimed at the treatment of tumours on and under the skin or on the lining of some internal organs. Depth of light penentration increases in the red part of the spectrum, thus the development of photosensitizers based on bacteriochlorophyll and metallic nanoparticles activated by infra-red radiation which will make it possible to increase the depth of photodynamic treatment several times.

Author

  • Shirinsky Vladimir P.

Sources

  1. Eljamel M. S. Brain phothodiagnosis (PD), fluorescence guided resection (FGR), and phothodynamic therapy (PDT): past, present and future // Photodiagnosis Photodyn. Ther. 2008. V. 5, №1. P. 29–35.
  2. Barr H., Dix A. J., Kendall C., Stone N. Review article: the potential role of photodynamic therapy in the management of upper gastrointestinal disease // Aliment. Pharmacol/Ther. 2001. V. 15, №3. P. 311–321.
  3. Kaplan M.A., Romanko Yu.S., Popuchiev V.V. Tsyb A.F. Photodynamic Therapy (in Russian). — Мoscow: Medicinskoe informacionnoe agentstvo, 2009.

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