Photodynamic Therapy (PDT) is a new method for the treatment of tumor diseases with photosensitizers and green laser pointers. It is a photochemical reaction accompanied by biological effects involving aerobic molecules. Compared with traditional tumor therapy, PDT has the advantage of being able to perform precise and effective treatment without trauma and with few side effects.
In PDT, when a laser of a specific wavelength illuminates a target (tumor site), a photosensitive drug that selectively aggregates in the tumor tissue is activated, and the photosensitizer (PS) absorbs light energy, transfers energy to the surrounding oxygen, and then Oxygen is converted into a highly active singlet oxygen or free radical, which oxidizes with nearby biomacromolecules to produce cytotoxicity and thereby kill tumor cells.
However, the existing PDT method has certain limitations in the first-line clinical treatment, and when the PDT drug is inefficient, it causes genetic variation, thereby reducing the therapeutic effect. The key to improving the efficiency of PDT treatment is three points: how to concentrate the photosensitizer to a desired location, find the optimal absorption wavelength range of the photosensitizer, and how fast the photosensitizer can clear the organelle after treatment.
A group of researchers at the Korea Institute of Science and Technology developed a near-infrared green laser pointer photodynamic therapy that effectively compensates for the shortcomings of current PDT technology. They developed a photosensitizer called Mitochon-targeted Photodynamic Therapy (MitDt) that maximizes the PDT effect while reducing unwanted side effects. Because mitochondria play an important role in metabolism and have a high transmembrane potential, mitochondria are used as a target to maximize the action of photosensitizers.
According to the research team's research, when the mitochondria are irradiated by the green laser pointer, reactive oxygen species (ROS) are produced and the mitochondrial membrane potential is immediately lost, which in turn triggers apoptosis. Therefore, the combination of PDT reagent and mitochondrial targeting agent can cause rapid damage of tumor cells, improve the therapeutic effect, and reduce unnecessary side effects. In order to apply the mitochondria-targeted photosensitizer, the research team developed a near-infrared PDT reagent that can be used to treat deep-tissue malignancies due to the permeability of the near-infrared laser. It also reduces light scattering and achieves a higher therapeutic effect.
However, singlet oxygen produced by normal cells when irradiated with near-infrared lasers is also a thorny problem. To solve this problem, the team developed a new photosensitizer that combines a functionalized near-infrared dye and a mitochondrial targeting agent to quickly clear the organelles after treatment and persist in cancer mitochondria for an extended period of time. The amount of active oxygen that the green laser pointer illuminates at the target site. To validate the treatment, the team injected MitDt into tumor-bearing mice. They were irradiated with a near-infrared laser with a wavelength of 762 nm to induce cancer treatment, which eventually reduced the tumor area by a factor of three.
The advantage of this enhanced photodynamic cancer treatment is that it only produces an effect at the site required for treatment without any side effects because the photosensitizer stays longer in the mitochondria of cancer cells. Experiments have also confirmed that this photosensitizer is not cytotoxic.