Bio-orthogonal phosphatidylserine conjugates for delivery and imaging applications

The syntheses of phosphatidylserine (PS) conjugates are described, including fluorescent derivatives for potential cellular delivery and bioimaging applications. Installation of terminal functional groups (amine, thiol, or alkyne) onto the sn-2 chain provides reactive sites for bio-orthogonal conjugation of cargo with suitably protected PS derivatives. An amine-containing PS forms amide bonds with peptidic cargo, a thiol derivative is designed for conjugation to cargo that contain alpha-halo carbonyls or Michael acceptors, and the terminal alkyne PS analogue permits "click" conjugation with any azide-tagged molecule. This latter conjugation method is quite versatile as it can be performed without PS headgroup protection, in aqueous media, and with acid-labile cargo.