Preparation of liposome bearing disulfide proteinoid and its reduction-responsive release property

Egg phosphatidylcholine (Egg PC) liposome bearing a disulfide proteinoid exhibited a reduction-responsive release property. Proteinoid composed of Asp, Leu, and cystamine (Prot(ALC)) and Asp and Leu (Prot(AL)) were synthesized by thermal condensation, confirmed by Raman, FT-IR, ¹H NMR and ¹³C NMR spectroscopy. Egg PC liposome bearing the proteinoid was prepared by a film hydration and sonication method. The fluorescence quenching of dye (i.e. calcein) loaded in liposome bearing the proteinoid was 68.1-78.1%. The mean hydrodynamic diameter of liposome bearing the proteinoid was less than 200 nm and it decreased with increasing amount of the proteinoid. On the TEM photo, multi-lamellar vesicles were observed and the vesicle diameter was 100-300 nm. At all the phospholipid to proteinod ratios tested (i.e. 1:0.01, 1:0.02, and 1:0.05 (w/w)), the release degree in 12 h of dye loaded in liposome bearing Prot(AL) was less than 2%, and it was almost the same regardless of dithiothreitol (DTT, a reducing agent) concentration (i.e. 0, 10, and 20 mM). Whereas the release degree of dye loaded in liposome bearing Prot(ALC) was 1.5-8.4% and it was significantly dependent on DTT concentration.