Facile Click-Mediated Cell Imaging Strategy of Liposomal Azido Mannosamine Lipids via Metabolic or Nonmetabolic Glycoengineering

Two Ac4ManNAz (AAM) derivatives with octadecanoic ester (C18 ester) and octadecyl ether (C18 ether) attached to the anomeric hydroxyl groups were synthesized and used in preparation of liposomes. Both liposomes show strong cell-labeling efficiencies on MDA-MB-231 cancer cells. The cell surface-anchored azide group can react with DBCO-Cy5 via Cu-free click chemistry. The two liposomes exhibit different azide placement mechanisms; C18-ether-AAM-treated cells have azido placement through direct insertion, while C18-ester-AAM-treated cells express azido more through metabolic glycoengineering.