Photouncaging of Carboxylic Acids from Cyanine Dyes with Near‐Infrared Light**

Abstract

Near‐infrared light (NIR; 650–900 nm) offers unparalleled advantages as a biocompatible stimulus. The development of photocages that operate in this region represents a fundamental challenge due to the low energy of the excitation light. Herein, we repurpose cyanine dyes into photocages that are available on a multigram scale in three steps and efficiently release carboxylic acids in aqueous media upon irradiation with NIR light up to 820 nm. The photouncaging process is examined using several techniques, providing evidence that it proceeds via photooxidative pathway. We demonstrate the practical utility in live HeLa cells by delivery and release of the carboxylic acid cargo, that was otherwise not uptaken by cells in its free form. In combination with modularity of the cyanine scaffold, the realization of these accessible photocages will fully unleash the potential of the emerging field of NIR‐photoactivation and facilitate its widespread adoption outside the photochemistry community.

Turning Red without Feeling Embarrassed─Xanthenium-Based Photocages for Red-Light-Activated Phototherapeutics

“…Last but not least, oxygen independency of the photorelease process should also be considered especially when the hypoxic environment of solid tumors is the target area . Some of these challenges were addressed recently with the development of novel photocages such as π-extended coumarin, − BODIPY, − and cyanine frames ,,, as well as metal-complex-based PPGs (see Figure for examples). ,− Unfortunately, advancement into one direction often results in the loss of other important features. In practice, this usually translates to PPGs with absorption bands >600 nm with improved aqueous solubilities but considerably decreased photocaging quantum yields .…”

“…A remarkable achievement was reported by Stacko et al recently. Their cyanine-based photocages possessed a considerably high uncaging efficiency upon NIR light irradiation . However, its dependency on molecular oxygen and limited payload tolerance due to the need for an early-stage synthetic installation of the cargo pose serious limitations toward their applications in hypoxic settings.…”

“…Their cyanine-based photocages possessed a considerably high uncaging efficiency upon NIR light irradiation. 33 However, its dependency on molecular oxygen and limited payload tolerance due to the need for an early- stage synthetic installation of the cargo pose serious limitations toward their applications in hypoxic settings. Another very recent work by Klań and Weinstain has highlighted the efficiency of porphyrin-based PPGs both in their all-organic or metal-complexed forms.…”

Red light induced folding of single polymer chains

“…27,28 While many cycloadditions have been constrained to higher energy wavelengths, photo-induced ligations using PPGs have been successfully performed with long wavelength visible (green and red) light to date. 25,26,[29][30][31][32][33][34][35] However, to the best of our knowledge, none of these visible-light induced reactions have been employed in single chain nanoparticle folding. Herein, we demonstrate the folding of SCNPs induced by red light (l max = 625 nm), which is the longest wavelength utilised to date.…”

New chemical tools to study RNA distribution in neuronal cells

“…They designed this novel PPG using DFT-based computational methods calculating frontier molecular orbital (FMO) uncaging with a similar cyanine photocage was not possible in a degassed medium a short time after. 75 The question regarding which proposed mechanism is the correct one will need to be discussed in future studies.…”