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

Abstract

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.

Trioxotriangulene with carbazole: a donor–acceptor molecule showing strong near-infrared absorption exceeding 1000 nm

“…π-Conjugated molecules showing NIR photoabsorption have been noticed in the research studies not only of organic electronic materials 5,29 but also of biological applications. 30 One of the molecular design strategies for NIR dyes is the extension of the π-conjugated systems as demonstrated in the polymeric fused porphyrin array (3500 nm, dodecamer) 31 and the giant hydrocarbon sheet (C 222 H 42 , 250-1400 nm). 32 The π-stacking assemblies of open-shell molecules also exhibit NIR absorption bands at 1000-2000 nm as shown in radical-ion salts of TTF and TCNQ 33 and also in TOT neutral radicals of our previous studies.…”

Long-wavelength photoremovable protecting groups: On the way to in vivo application

“…If the sole photon energy is not sufficient to bond breaking, additional photochemical transformations are essential for uncaging [26]. For instance, benzoquinone-based photocage, first introduced in 2006 [27], undergoes photocyclization at 458 nm and then thermal elimination of LG.…”

Shining a Light on Bioorthogonal Photochemistry for Polymer Science

“…[37] Owing to these limitations, only select examples of 2PA systems of key interest will be highlighted in this review, and interested readers are referred to more focused reviews on this topic. [33,37]…”