Visible-light activatable coumarin-based phototriggers for fluorescence imaging with ultra-high photolysis efficiency

Photoactivated fluorophores (PAFs) are powerful imaging tools for observing subcellular structures and tracking dynamic biological processes. However, photoremovable protecting groups (PPGs) widely used to construct PAFs suffer from the drawbacks of short-wavelength excitation and/or low photolysis efficiency. Herein, a class of coumarin-based PPGs with electron-rich thiophene derived substitutions at the C3-position of a coumarin scaffold were prepared. The modification not only leads to the redshift of the absorption band to the blue light region (400-500 nm), but also the increases of uncaging quantum yield (f(u)) as well as molar extinction coefficient (e(max)), thus enhancing the photolysis efficiency (f(u) x e(max)) up to 34.2 x 10(3) M-1 cm(-1). The exceptionally high photolysis efficiency enables efficient photolysis in blue light as weak as 2 mW cm(-2) or in blue light from a Luminol chemiluminescence system. Based on the excellent photolysis properties, the PAF constructed by the new PPG exhibits fast photoactivation and a low background signal, and the resulting fluorescence images display a signal-to-noise ratio greater than 780. It is anticipated that the superior photolysis performance makes the PPGs a novel platform for the construction of photo responsive systems in a variety of applications.

Automated summary

Photoactivated fluorophores (PAFs) have great potential as imaging tools for subcellular structures and dynamic biological processes. However, the current photoremovable protecting groups (PPGs) used in PAF construction have limitations in terms of excitation wavelength and efficiency. In this study, a new class of coumarin-based PPGs with electron-rich thiophene derived substitutions was developed to address these limitations. The modified PPGs showed redshifted absorption and increased photolysis efficiency, enabling efficient photolysis even under weak blue light. The resulting PAF exhibited fast photoactivation, low background signal, and high signal-to-noise ratio in fluorescence imaging. It is anticipated that these superior photolysis properties make the PPGs a novel platform for constructing photoresponsive systems in various applications.