Near-infrared radiation (NIR) (NIR)

Near-infrared (NIR) photons are a form of electromagnetic radiation with wavelengths typically ranging from 700 nm to 2500 nm, situated between the visible and microwave regions of the spectrum (Hamblin, 2017). While not a biological molecule or receptor, NIR light serves as a critical physical stimulus in medical therapies such as photobiomodulation (PBM) and photodynamic therapy (PDT) (NCI, 2023). In PBM, NIR photons are absorbed by endogenous mitochondrial chromophores, specifically cytochrome c oxidase, which enhances electron transport and increases adenosine triphosphate (ATP) production to promote tissue repair and reduce inflammation (Hamblin, 2017). In the context of oncology, NIR light is used to activate exogenous photosensitizing drugs, triggering the production of cytotoxic reactive oxygen species (ROS) that lead to targeted tumor destruction (NCI, 2023). The primary advantage of NIR photons in clinical use is their optical window, which allows for deeper tissue penetration than visible light, though safety concerns include potential thermal injury and retinal damage (Wang et al., 2019). Furthermore, NIR photons are increasingly utilized in diagnostic imaging and real-time surgical guidance due to their ability to excite fluorescent contrast agents like indocyanine green (Zhu et al., 2018). This dual role in therapy and diagnostics makes NIR radiation a cornerstone of modern biophotonics and theranostic applications.

Other names

Near-infrared lightNIR photonsNear-IRNear-infrared energy

NIR photons function as a physical trigger that is absorbed by specific chromophores; in photobiomodulation, they target mitochondrial cytochrome c oxidase to increase ATP and signaling molecules, while in photodynamic therapy, they excite photosensitizers to generate cytotoxic singlet oxygen (Hamblin, 2017; NCI, 2023).