Membrane curvature enhances oxidation within lipid bilayers in a composition-dependent manner.

Excessive production of reactive oxygen species (ROSs) in cells results in oxidative stress, which can promote lipid oxidation in cellular membranes. This oxidation of membrane lipids accompanies various diseases and can even result in cell death through processes such as ferroptosis. The complex compositions and diverse morphologies of cellular membranes make understanding the mechanisms of lipid oxidation challenging, especially when attempting to investigate membrane composition and curvature simultaneously. Here, we utilize reconstituted lipid membranes and the fluorescent oxidation probe C11-BODIPY to quantify membrane-associated oxidative responses in lipid bilayers as functions of both lipid composition and membrane curvature. By tethering synthetic lipid vesicles to glass substrates, we were able to monitor C11-BODIPY oxidation on a per-vesicle basis using fluorescence microscopy. Our results demonstrate that highly curved membranes markedly increase both the rate and extent of C11-BODIPY oxidation across diverse membrane compositions. This curvature dependence is consistent with increased lipid-tail exposure and enhanced access of ROS-associated chemistry to the interfacial/hydrophobic region of the bilayer. Compositional effects on C11-BODIPY oxidation are most pronounced in membranes with low curvature (i.e., diameter greater than 100 nm) and become progressively weaker as curvature increases. We also found that cholesterol suppressed C11-BODIPY oxidation in unsaturated phosphatidylcholine membranes across all curvature regimes, highlighting how sterol content can tune oxidative susceptibility. Together, these findings support a model in which membrane curvature and lipid composition act as interdependent determinants of membrane-associated oxidative susceptibility, offering new insight into simplified lipid systems.