Photodynamic therapy (PDT) is a form of phototherapy involving light and a photosensitizing chemical substance used in conjunction with molecular oxygen to elicit cell death (phototoxicity).
PDT is used in treating acne, wet age-related macular degeneration, psoriasis, and herpes. It is used to treat malignant cancers, including head and neck, lung, bladder and skin.
Cancer treatments are a wide range of treatments available for the many different types of cancer, with each cancer type needing its own specific treatment. Treatments can include surgery, chemotherapy, radiation therapy, hormonal therapy, targeted therapy including small-molecule drugs or monoclonal antibodies, and PARP inhibitors such as olaparib. Other therapies include hyperthermia, immunotherapy, photodynamic therapy, and stem-cell therapy. Most commonly cancer treatment involves a series of separate therapies such as chemotherapy before surgery. Angiogenesis inhibitors are sometimes used to enhance the effects of immunotherapies.
The choice of therapy depends upon the location and grade of the tumor and the stage of the disease, as well as the general state of the patient. Biomarker testing can help to determine the type of cancer, and indicate the best therapy. A number of experimental cancer treatments are continuously under development. In 2023 it was estimated that one in five people will be diagnosed with cancer at some point in their lifetime.
Singlet oxygen, systematically named dioxygen(singlet) and dioxidene, is a gaseous inorganic chemical with two oxygen atoms in a quantum state where all electrons are spin-paired, known as a singlet state. It is the lowest excited state of the diatomic oxygen molecule, which in general has the chemical structure O=O and chemical formula O
2. Singlet oxygen can be written more specifically as
[O
2] or
O
2. The more prevalent ground state of O
2 is known as triplet oxygen. At room temperature, singlet oxygen will slowly decay into triplet oxygen, releasing the energy of excitation.
Singlet oxygen is a gas with physical properties differing only subtly from the ground state. In terms of its chemical reactivity, however, singlet oxygen is far more reactive toward organic compounds. It is responsible for the photodegradation of many materials but can be put to constructive use in preparative organic chemistry and photodynamic therapy. Trace amounts of singlet oxygen are found in the upper atmosphere and in polluted urban atmospheres where it contributes to the formation of lung-damaging nitrogen dioxide. It often appears and coexists confounded in environments that also generate ozone, such as pine forests with photodegradation of turpentine.