Mitochondria-Targeted COUPY Photocages: Synthesis and Visible-Light Photoactivation in Living Cells

Abstract

Releasing bioactive molecules in specific subcellular locations from the corresponding caged precursors offers great potential in photopharmacology, especially when using biologically compatible visible light. By taking advantage of the intrinsic preference of COUPY coumarins for mitochondria and their long wavelength absorption in the visible region, we have synthesized and fully characterized a series of COUPY-caged model compounds to investigate how the structure of the coumarin caging group affects the rate and efficiency of the photolysis process. Uncaging studies using yellow (560 nm) and red light (620 nm) in phosphate-buffered saline medium have demonstrated that the incorporation of a methyl group in a position adjacent to the photocleavable bond is particularly important to fine-tune the photochemical properties of the caging group. Additionally, the use of a COUPY-caged version of the protonophore 2,4-dinitrophenol allowed us to confirm by confocal microscopy that photoactivation can occur within mitochondria of living HeLa cells upon irradiation with low doses of yellow light. The new photolabile protecting groups presented here complement the photochemical toolbox in therapeutic applications since they will facilitate the delivery of photocages of biologically active compounds into mitochondria.

Construction of a coumarin-based fluorescent probe for accurately visualizing hydrogen sulfide in live cells and zebrafish

“…Trifluoromethyl coumarin, with the advantages of high chemical stability, wide emission wavelength range, and high fluorescence quantum yield, has been widely used in bioimaging and fluorescent probes. 26–31 In this work, we designed and synthesized a novel coumarin-based fluorescent probe Cou-H 2 S using trifluoromethyl coumarin as the molecular scaffold and 2-pyridyl disulfide as the H 2 S recognition group (Scheme 1). The reaction of Cou-H 2 S with H 2 S released a trifluoromethyl coumarin dye that emitted intense fluorescence at 498 nm.…”

Photoactivable AIEgen-based Lipid-Droplet-Specific Drug Delivery Model for Live Cell Imaging and Two-Photon Light-Triggered Anticancer Drug Delivery

“…Recently, near-infrared light-responsive drug delivery systems (DDSs) operated in the “phototherapeutic window” (600–950 nm) via a two-photon process for cancer treatment have emerged as a powerful tool. − , Two-photon responsive DDSs provide excellent advantages like (i) being capable of releasing drugs in three dimensions with spatial and temporal precision, (ii) deep tissue penetration, (iii) reduction of the illumination duration, causing lesser damage to the biological systems, and (iv) imaging of live cellular processes at high spatiotemporal resolution. − In general, two-photon responsive DDSs for releasing anticancer drugs are constructed using photoremovable protecting groups (PRPGs), namely o-nitrobenzyl, nitroindoline, coumarin, quinoline, and o -hydroxycinnamic acid derivatives. − Notably, the light-responsive drug delivery systems developed so far have no inherent ability to differentiate cancerous cells and normal cells unless they are decorated by ligands that can interact with receptors overexpressed in cancer cells. , By any means, if we can design and develop light-responsive DDSs, which can selectively monitor the dynamic LDs in the cancer cells and efficiently release anticancer drugs, they will be in great demand in cancer treatment. For this purpose, we have developed the LD-specific NIR light-responsive DDSs based on naturally occurring chalcone derivatives.…”

“…Recently, near-infrared light-responsive drug delivery systems (DDSs) operated in the "phototherapeutic window" (600−950 nm) via a two-photon process for cancer treatment have emerged as a powerful tool. [21][22][23][24]6 Two-photon responsive DDSs provide excellent advantages like (i) being capable of releasing drugs in three dimensions with spatial and temporal precision, (ii) deep tissue penetration, (iii) reduction of the illumination duration, causing lesser damage to the biological systems, and (iv) imaging of live cellular processes at high spatiotemporal resolution. 25−28 In general, two-photon responsive DDSs for releasing anticancer drugs are constructed using photoremovable protecting groups (PRPGs), namely onitrobenzyl, nitroindoline, coumarin, quinoline, and o-hydroxycinnamic acid derivatives.…”

Exploring Structural–Photophysical Property Relationships in Mitochondria-Targeted Deep-Red/NIR-Emitting Coumarins

“…While the ortho-pyridinium and the ortho,ortho-pyrimidinium analogs underwent a blueshift in the absorption and emission maxima, the ortho,para-pyrimidinium analogs exhibited a redshifted absorption and emission, and higher photostability and selectivity for mitochondria than the parent para-pyridinium compound [31]. COUPY dyes have been successfully employed to fluorescently label biomolecules, such as peptides and lipids [32], to develop photosensitizers for anticancer PDT [33,34] and as mitochondria-targeted photolabile protecting groups [35].…”