Photodynamic therapy and photobiomodulation: Can all diseases be treated with light?

Visible and near-infrared light may be able to treat all (or nearly all) human diseases. Light plus nontoxic dyes called photosensitizers (PS) can kill cancer cells, inactivate a broad-spectrum of pathogens and destroy unwanted tissue using a process called photodynamic therapy (PDT). The mechanism involves photochemical generation of a range of reactive oxygen species including singlet oxygen and hydroxyl radicals. Due to the alarming worldwide rise in multi-antibiotic resistance in bacteria. PDT has emerged as a promising alternative for localized infections. It has been observed that antigen-specific immune response against cancer can be potentiated by PDT. Moreover a non-specific protective immune response against infection has also been observed. In contrast light alone in a process called photobiomodulation (PBM) or low level light therapy (LLLT) can reduce inflammation and pain, stimulate healing and tissue repair. Mechanisms involve photon absorption in mitochondrial cytochrome c oxidase, melanopsin, and transient receptor potential ion channels. Stem cells are particularly sensitized to light activation. Many different diseases and injuries can be benefited including wound healing, arthritis, spinal cord injury, muscle fatigue, and neuropathic pain. Brain disorders respond very well, such as traumatic brain injury, Alzheimer’s disease, depression, and PTSD. PBM can increase brain-derived neurotrophic factor, neurogenesis, and synaptogenesis.