Photodynamic therapy

The Photodynamic therapy (PDT) is a form of photo therapy. It involves light and photo sensitizing chemical substances. It is used in conjunction with molecular oxygen to elicit (draw out) cell death.

Applications

• The therapy is popularly used in treating acne.
• It is also used treat wide range of medical conditions. This includes psoriasis, wet age-related macular degeneration, atherosclerosis.
• It is also used in treating herpes, malignant cancer in neck, head, bladder, lung and skin.
• It is minimally toxic and minimally invasive.

Role of photosensitizers in PDT

• The PDT uses photosensitizers. The photosensitizers are molecules that absorb light, transfer its energy into another molecule. In radiation therapy, the cell is killed or damaged by targeting the cell DNA. The photosensitizers target the other parts of the cell.
• The photosensitizers are used to sterilize blood plasma to remove viruses and blood borne viruses.
• The other light based and laser therapies such as intense pulsed light do not require photosensitizer.

How does PDT work?

• The PDT is a multi stage process. It involves three components namely photo sensitizer, oxygen and light source.
• When light is focused on the photosensitizers, they either donate electrons to the substrate or gain an electron from the substrate.
• During PDT, first the photosensitizer is administered. When considerable amount of photosensitier is absorbed in the diseased tissue, the photosensitizer is activated by exposing light for a specified period.

Recent developments in PDT

The PDT is used to destroy malignant cancer cells. The strangest side effects of PDT is that the patients are able to see better in dark. Recently, researchers have found why this happens. This is because Rhodopsin, a light sensitive protein in the retina of eyes interacts with photosensitive compound called chlorin e6. Even a small light or little light will trigger retina to separate from rhodopsin. This is converted into electrical signals in brain.