PKH 26

PKH 26 (CAS No.: 154214-55-8) is a lipophilic red fluorescent membrane dye widely utilized in biomedical research for stable labeling of cell membranes through its strong affinity for lipid bilayers, where it integrates into the hydrophobic regions and emits red fluorescence with excitation and emission maxima at approximately 551/567 nm. Classified as a fluorescent cell-tracking probe, PKH 26 exhibits prolonged membrane retention and minimal transfer between adjacent cells, enabling long-term monitoring of labeled populations; notably, its extended persistence has been demonstrated in erythrocyte membranes with half-lives exceeding several weeks in experimental systems. Mechanistically, PKH 26 functions through passive insertion into lipid domains rather than binding to specific molecular targets or signaling pathways, making it particularly suitable for studies of cell proliferation, lineage tracing, membrane dynamics, and cell trafficking. The dye is frequently applied in flow cytometry-based assays, including evaluation of T cell-mediated cytotoxicity, as well as fluorescence microscopy and in vivo or ex vivo tracking experiments. Effective working concentrations typically fall within low micromolar ranges depending on cell type and assay conditions, and experimental parameters such as labeling duration and dye concentration should be optimized to balance fluorescence intensity with cellular viability and functional integrity.