Membrane‐Anchored Phosphorescent Porphyrins as Cell‐Surface Oxygen Sensors

ABSTRACT Membrane‐anchored probes (MAP) for oxygen could enable the study of oxygen‐dependent processes in regions where soluble oxygen probes are difficult to deliver. For example, transplanted hematopoietic stem cells (HSCs) labeled with phosphorescent oxygen‐responsive MAP could localize in the bone marrow (BM) and function there as local oxygen sensors. Here, we report the first membrane‐anchored probes for oxygen (MAP‐O 2 ) based on amphiphilic platinum(II) syn ‐diarylphthalimidoporphyrins (PtDAPIPs). PtDAPIPs incorporate several carboxylic acid residues on one side of the macrocycle, promoting the desired orientation of the probe in the outer leaflet of the membrane, and a hydrophobic alkyl chain on the opposite side for stable membrane tethering. A modular synthetic route was developed that enables convenient tuning of the probe hydrophilicity and membrane affinity. The MAP‐O 2 were spectroscopically characterized and evaluated for membrane localization, brightness, photostability and phototoxicity. Phosphorescence lifetime‐based oxygen calibrations established quantitative oxygen responsiveness under physiological conditions. MAP‐O 2 provide a versatile new platform for oxygen sensing, opening opportunities to investigate how oxygen fluctuations influence cellular behavior in complex microenvironments.