Special topic | Photodynamic therapy - a tool for precise tumor therapy

Let the tumor "see the light to die"

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Photodynamic therapy (PDT) is a clinically approved non-invasive tumor treatment method that selectively kills tumor cells. Compared with traditional radiotherapy and chemotherapy, it has the characteristics of minimally invasive/non-invasive, targeted therapy, and high applicability.

During treatment, photosensitive drugs are first applied or injected intravenously. Photosensitive drugs will accumulate in the lesion tissue, selectively, in high concentration and for a long time (most of them will be excreted within 24-48 hours); The Laser of a specific wavelength is used to irradiate the surface of the tumor tissue or the Optical Fiber is inserted into the tumor for irradiation. The photosensitizer absorbs the laser energy and undergoes a series of chemical reactions to generate highly active singlet oxygen and free radicals, thereby killing tumor cells and turning the tumor into a tumor. Necrotic tissue, which then peels off, falls off, or is absorbed by the body.

Photodynamic therapy has three essential elements - "light source, photosensitizer, singlet oxygen". Among them, the light source is an important energy source. Due to the low incoherent light intensity, poor monochromaticity, and low fiber coupling efficiency, lasers are used as excitation light sources in current research and clinical practice.
The wavelength of the laser light source should be selected according to the absorption peak of the photosensitizer. The correctness of the wavelength, the tissue penetration, the stability of the output power, the uniformity of the spot, etc. are all important and reliable factors for the treatment effect. Due to its small size, high stability, high fiber coupling efficiency, and strong environmental adaptability, semiconductor lasers have replaced the bulky and inconvenient argon-ion laser-pumped dye laser systems in clinical translation, and have become the current tumor light source. The light source of choice for dynamic therapy.