Liposome surface functionalization facilitates the enormous potential applications of liposomes, such as stabilizing and targeting carrier systems for delivering active molecules in biomedical research and applications. Cell surface carbohydrates have been an attractive model system for liposome surface functionalization for enhanced biomedical applications, such as site-specific and ligand-directed drug and gene delivery, multivalent inhibition, and vaccine adjuvant applications. The present protocol describes an efficient and chemically selective liposome surface glyco-functionalization method based on Staudinger ligation performed in phosphate-buffered saline buffer (pH 7.4) at room temperature. Specifically, a carbohydrate derivative carrying a spacer with an azide group is conjugated onto the surface of preformed liposomes carrying terminal triphenylphosphine groups. The compatibility of the reaction conditions for liposome surface functionalization was confirmed with dynamic light scattering and kinetic experiments monitoring the leakage of entrapped 5,6-carboxyfluorescein.
