In situ polycondensation of amino acid modified liposomes and their properties

Three amphiphilic amino acids based on glutamic acid, i.e. S-1-carboxy-2-(N-bistetradecyl- -glutamate]carbon-yl)ethyl]cysteine (1), S-1-carboxy-2-(N-bishexadecyl- -glutamate]carbonyl)ethyl]cysteine (2), S-1-carboxy-2-(N-bis-octadecyl- -glutamate]carbonyl)ethyl]cysteine (3), were synthesized. The aggregation behavior of them in water or buffer solution was studied. It was found that upon hydration and sonication in water, they could form stable liposomes. This kind of amino acid modified liposome was then polycondensed locally on the liposome surface to form a polypeptide-surfaced liposome and the peptide formation was detected by Fr-IR, GPC, etc. The effect of polycondensation of amino acid on the properties of liposomes were studied by detecting the phase transition temperatures with DSC or measuring the leakage of the encapsulated fluorescent probe from the liposomes. It was observed that the phase transition temperatures of the peptide liposomes moved down and the polycondensation of amino acid moieties obviously increased the leakage of the encapsulated molecules.