Near-IR Photochemistry for Biology: Exploiting the Optical Window of Tissue.

Photoactive molecules enable much of modern biology and biochemistry-a vast library of fluorescent chromophores is used to track and label cellular structures and macromolecules. However, photochemistry is better known to the synthetic or physical organic chemist as a "light switch" that turns on unusual excited-state reactivity, isomerization, or dynamic adjustment of structure. This review details a rapidly growing approach to biophotochemistry that uses low-energy near-IR wavelengths not only for imaging, but also for close spatial control over chemical switching events in biosystems. Emphasis is placed on topics of biomedical interest: release of gaseous biological messengers, uncaging of drugs, nano-therapeutics, and modification of biomaterials.