SULFATED N-MYRISTOYL CHITOSAN AS A SURFACE MODIFIER OF LIPOSOMES

Sulfated N-myristoyl chitosan (S-M-chitosan), which is strongly electr olytic and water soluble as well as partly hydrophobic due to long alk yl chains, was synthesized to be used as a liposome-surface modifier. The effects of the treatment with an aqueous S-M-chitosan solution on the stability of the liposome suspension prepared from hydrogenated eg g yolk lecithin were examined on several points. A suspension of large liposomes prepared by the Bangham method was precipitated by standing for a day, but the precipitation was restrained when the sample was t reated with S-M-chitosan solution. The turbidity of a small liposome s uspension was changed greatly after the suspension was freeze-thawed, but the change was small in the treated sample. A similar result was o btained when the suspension was freeze-dried following the addition of water. These results come from the facts that the surface of the lipo some was coated with S-M-chitosan and negatively charged as ascertaine d by the measurement of zeta potential and the electron microscopic ob servation. The repulsive force between charges was considered to be th e origin of the stabilization. It was also shown from an ESR experimen t that the treatment suppressed the elution rate of the material incor porated into the liposomes.