We are pleased to announce the publication of a new research article entitled “Stiffening cells with light”, resulting from a collaboration with Julien Husson at École Polytechnique.

Summary: Fluorescence microscopy is commonly used to observe living cells and organisms, but it can induce phototoxicity, which may lead to erroneous interpretations. The primary cause of phototoxic cell damage is the production of reactive oxygen species (ROS), which can crosslink intracellular proteins and nucleic acids. Using profile microindentation and atomic force microscopy, we demonstrate that excitation of various fluorescent probes causes a rapid dose-dependent increase in cell stiffness across multiple cell types. This photostiffening effect explains why T cells loaded with the Fluo-4 calcium probe stop protruding within seconds after light excitation. We show that upon fluorophore excitation, ROS production is correlated with increased stiffness, and we reproduce the effect by incubating cells with H₂O₂ or the photosensitizer pheophorbide a. This study underscores the importance of controls and proposes photostiffening as a method for quantifying phototoxicity.

🔗 Article
🔗 École Polytechnique news
🔗 Julien Husson’s website

Image credits: Julien Husson. Cover image from Cell Reports Physical Science.