Mucoadhesive chitosan-coated liposomes: characteristics and stability

Lecithin liposomes, empty or containing FITC-dextran, were prepared by the ethanol injection method. Three different types of chitosans with different molecular weight and degrees of deacetylation were used (Seacure 113, 210 and 311). Chitosan coating was carried out by mixing the liposomal suspension with the chitosan solution followed by incubation. The size of liposomes was measured before and after polymer coating by an image analysis technique. The mean diameter of liposomes containing FITC-dextran was in the size range 250-280nm, whereas the size after coating was 300-330nm, regardless of chitosan type. All chitosan-coated liposomes were of spherical shape and no morphological differences between uncoated and coated liposomes were observed. Liposomes with FITC-dextran, originally entrapping 50% of the marker substance taken in the preparation and coated in the presence of unentrapped marker substance, contained 60-65%of the marker substance. The highest entrapment was found for liposomes coated with medium molecular weight chitosan. The stability of chitosan-coated liposomes in simulated gastric fluid was significantly higher as compared to uncoated liposomes. One can conclude that chitosan is stabilizing the original liposomal structure and protecting liposomally entrapped drug.