Phosphatidylserine exposure and plasma membrane perforation as ferroptotic signatures for in vivo imaging.

Ferroptosis emerged as a cell death modality against cancer, but there are currently no available biomarkers for imaging ferroptosis-based therapies. To address this, we evaluated phosphatidylserine exposure and perforation of lipid membranes during ferroptosis to explore potential targeting opportunities. We demonstrated that nano-sized gaps at late stage ferroptosis can serve as entry points for dyes that can bind to intracellular structures. These changes were accompanied with cellular signaling components similar to platelet activation, with phosphatidylserine exposure on the cell surface as a potential target for imaging programed cell death, including ferroptosis. We employed a novel tumor-seeking dye CJ215 that can also label apoptotic cells and showed that CJ215 accumulates in ferroptotic cells both in vitro and in vivo by binding to phosphatidylserine, which can be prevented with ferroptosis inhibition. Since phosphatidylserine exposure also occurs during apoptosis, CJ215 can monitor both apoptosis and ferroptosis-based therapies.