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Updated: Mar 24, 2026
Detection of Mitochondria Membrane Potential to Study CLIC4 Knockdown-induced HN4 Cell Apoptosis In Vitro
Published on: July 17, 2018
Mitochondria-targeted Triphenylamine Derivatives Activatable by Two-Photon Excitation for Triggering and Imaging Cell
Rahima Chennoufi1, Houcine Bougherara1, Nathalie Gagey-Eilstein1
1LBPA, CNRS UMR8113, IDA FR3242, ENS Cachan, Université Paris-Saclay, F-94235 Cachan, France.
Abstract:
Photodynamic therapy (PDT) leads to cell death by using a combination of a photosensitizer and an external light source for the production of lethal doses of reactive oxygen species (ROS). Since a major limitation of PDT is the poor penetration of UV-visible light in tissues, there is a strong need for organic compounds whose activation is compatible with near-infrared excitation. Triphenylamines (TPAs) are fluorescent compounds, recently shown to efficiently trigger cell death upon visible light irradiation (458 nm), however outside the so-called optical/therapeutic window. Here, we report that TPAs target cytosolic organelles of living cells, mainly mitochondria, triggering a fast apoptosis upon two-photon excitation, thanks to their large two-photon absorption cross-sections in the 760-860 nm range. Direct ROS imaging in the cell context upon multiphoton excitation of TPA and three-color flow cytometric analysis showing phosphatidylserine externalization indicate that TPA photoactivation is primarily related to the mitochondrial apoptotic pathway via ROS production, although significant differences in the time courses of cell death-related events were observed, depending on the compound. TPAs represent a new class of water-soluble organic photosensitizers compatible with direct two-photon excitation, enabling simultaneous multiphoton fluorescence imaging of cell death since a concomitant subcellular TPA re-distribution occurs in apoptotic cells.
Insights
Triphenylamines (TPAs) are novel organic photosensitizers that induce cell death via reactive oxygen species (ROS) production. These compounds are activated by near-infrared light, overcoming limitations of traditional photodynamic therapy (PDT).
Area of Science:
- Biochemistry
- Cell Biology
- Photochemistry
Background:
- Photodynamic therapy (PDT) utilizes photosensitizers and light to generate reactive oxygen species (ROS) for cell death.
- Current PDT faces limitations due to poor light penetration in tissues, necessitating near-infrared (NIR) activatable compounds.
- Triphenylamines (TPAs) are fluorescent organic compounds previously shown to induce cell death with visible light.
Purpose of the Study:
- To investigate TPAs as photosensitizers activated by two-photon excitation in the NIR range (760-860 nm).
- To evaluate the mechanism of TPA-induced cell death, focusing on ROS production and mitochondrial apoptosis.
- To explore the potential of TPAs for simultaneous multiphoton fluorescence imaging of cell death.
Main Methods:
- Two-photon excitation of TPAs in living cells.
- Direct reactive oxygen species (ROS) imaging.
- Three-color flow cytometry to detect phosphatidylserine externalization.
- Subcellular TPA redistribution analysis during apoptosis.
Main Results:
- TPAs target cytosolic organelles, primarily mitochondria, inducing rapid apoptosis upon two-photon excitation.
- TPA photoactivation generates ROS, initiating the mitochondrial apoptotic pathway.
- Observed differences in cell death kinetics depending on the specific TPA compound.
- TPAs enable simultaneous multiphoton fluorescence imaging of cell death due to redistribution in apoptotic cells.
Conclusions:
- TPAs are a new class of water-soluble organic photosensitizers compatible with two-photon excitation in the NIR window.
- TPAs effectively induce apoptosis via ROS production, primarily through the mitochondrial pathway.
- These compounds offer potential for advanced photodynamic therapy and real-time cell death imaging.
