Killing cancer cells with light

  Humans have always been “smell cancerous.” According to the International Agency for Research on Cancer, in 2012, there were 14.1 million new cancer cases and 8.2 million cancer deaths worldwide. Traditional treatments, including radiotherapy, chemotherapy, surgical resection, etc., can cause side effects and pain to patients. Scientists have been exploring a more effective new way to help humans fight this demonic. The emergence of photodynamic therapy has opened a breakthrough for scientists and brought hope to mankind.
  Photodynamic therapy for cancer
  photodynamic therapy, photosensitizing drugs is a new method and a light irradiation treatment of tumor diseases. The first is by injecting a drug called a photosensitizer, which has a different half-life in each tissue. After a certain period of time, the concentration of photosensitizer in the tumor tissue is higher than that of the surrounding normal tissue. Then, the visible light of the specific wavelength is used to irradiate the surface of the tumor tissue, or the optical fiber is inserted into the inside of the tumor for irradiation, the photosensitizer absorbs visible light, catalyzes a series of chemical reactions of the surrounding oxygen, and generates a cytotoxic substance such as singlet oxygen, which can destroy The microvessels in the cancer tumor kill the tumor cells and achieve the purpose of local cancer treatment.
  Photodynamic therapy has the advantages of minimally invasive, high efficacy and low toxic and side effects, which can alleviate the pain of patients in the treatment process, and is expected to become an important means of modern cancer treatment.
  However, there are still many shortcomings in current photodynamic therapy, such as poor penetrability and low targeting. The photosensitizer needs to absorb visible light, and the visible light has poor penetrating ability in the human tissue, and the treatment cannot penetrate into the tissue, and is mostly limited to the tumor site in the epidermis or the shallow tissue region. In addition, in order to access internal lesions, an endoscope is typically used to introduce an optical fiber into the body, providing short-term but intense light illumination. However, during the course of treatment, due to the spontaneous movement of the organ (such as peristalsis and spontaneous contraction), the distance between the fiber and the target organ is constantly changing, and this uncertainty causes the light to be too thin or too dense. If it is too sparse, the treatment effect is insufficient; if it is too dense, it will cause organ dysfunction.
  In order to improve the reliability and safety of photodynamic therapy, metronome photodynamic therapy (mPDT) has emerged, which provides long-term low-light illumination, so that damage due to excessive light exposure is negligible. However, this method requires a device that can provide a light source reliably for a long period of time, and can be accurately attached to the target organ, which is a big challenge for scientists, after all, for some fragile organs, surgical suture The way to stitch the illuminating device to the target organ is unreliable.
  Recently, scientists have invented a fully implantable wirelessly driven nanochip device with nanomaterials, which is expected to solve this problem. This device is similar to the shape of a sandwich with a wirelessly driven light-emitting diode chip (LED) in the middle, with polydimethylsiloxane (PDMS) nanosheets surface-modified with polydopamine (PDA) on both sides and unmodified Polydimethylsiloxane (PDMS). Polydopamine is a bioadhesive material inspired by mussel adhesion proteins, which is bioadhesive and adheres well to the surface of tissues in vivo.
  Scientists implanted the device subcutaneously in mice to perform metrological photodynamic therapy on tumors transplanted into the skin. The results show that the device can provide a continuous light source deep inside the tissue and remain attached to the surface of the tissue for a long time. The therapeutic effect is good, and it is especially useful for treating cancer in fragile organs such as brain and pancreas. Scientists say the new technology will provide a new way to treat undetectable microscopic tumors or deep lesions that are unreachable by light.