Impact of lipid conjugation on the membrane selectivity of phospholipid sensors

Phosphatidylserine is the major anionic phospholipid exposed on the surface of mammalian cells during biological processes such as apoptosis.1 The zinc(II) dipicolylamine (ZnDPA) fluorescent sensors are widely employed tools to detect PS on artificial membranes2, 3 and cellular surfaces.2, 4-7 Introducing diverse lipid anchors to fluorophores influences their cellular uptake8 and sub-cellular localization.9 However, the impact of conjugating ZnDPA fluorescent sensors with lipids on their phosphatidylserine selectivity and cellular uptake remains elusive. In this study, we systematically introduced different lipid anchors to ZnDPA fluorescent sensors and performed liposome- and cell-based experiments to determine the impact of lipid anchors on anionic lipid selectivity, membrane leakage, and permeability. We found that long-chain fatty acid conjugated ZnDPA sensors do not distinguish anionic membranes as effectively. Furthermore, cellular uptake and plasma membrane retention of ZnDPA sensors can be significantly modulated depending on the type of lipid conjugation used. Importantly, surface-exposed phosphatidylserine alters the cellular uptake of medium-chain lipid anchor conjugated ZnDPA sensors. Thus, our study advances our understanding of how to select specific lipid anchors to optimize the design of ZnDPA-based sensors for different research goals.