Photouncaging of Carboxylic Acids from Cyanine Dyes with Near-Infrared Light

Abstract

Near-infrared light (NIR; 650–900 nm) as biocompatible stimulus offers unparalleled advantages in terms of availability, high precision in time and space and deep tissue penetration. The development of photocages that operate in this region represents a fundamental challenge due to 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 independent techniques and we provide compulsive evidence that it proceeds via photooxidative pathway. In vitro biocompatibility of the photocages and their photoproducts is also demonstrated. In combination with modularity of the cyanine scaffold, the realization of these accessible photocages will aid fully unleashing the potential of the emerging field of NIR-photoactivation and facilitate its widespread adoption outside the photochemistry community.