Abstract
In this study, we attempted to develop a liposome which showed a responsiveness to membrane-fluidity to amino acids as a NMF component in the human skin. Amino acids have an amphoteric charge in solution. Therefore, we considered that the liposomes were given a one-sided electrical charge and controlled on the surface charge, so that their membrane-properties were varied by electrostatic forces of attraction or repulsion with the electric charges of amino acids. First, we investigated the constituent of the liposome with responsiveness to outer conditions. It was found that the liposomes containing the Dipalmitoyl phosphatidic acid (PA) showed the most effective responsiveness to 5,(6)-Carboxyfluorescein (CF) leakage. Further, it was indicated that the surface charge and the microfluidity in the vicinity of the polar group affected the CF leakage. Next, we investigated the membrane-fluidity in the presence of amino acids, expecting that the membrane-fluidity was controlled by neutralization or the increase of the surface charge with the electrical charges of amino acids. As a result, the promotion of the leak was seen in the presence of an acidic amino acid (Asp) having a negative charge. On the other hand, the depression of the leak was seen in the presence of a neutral amino acid (Gly) or a basic amino acid (Lys) having a neutral or a positive charge, respectively. Lys was the most effective on the depression of the leak. Moreover, we found that the microfluidity in the vicinity of the polar group affected the depression of CF leakage. It was assumed that the depression of leakage was due to the neutralization of the surface charge and the decrease of the microfluidity in the presence of the neutral amino acid or the basic amino acid. In conclusion, we confirmed that the liposome which showed responsiveness to amino acids was prepared by mixing PA into PC liposome.
