Effect of mono- and double-layer polysaccharide surface coating on the physical stability of nanoliposomes under various environments

Physical stability is an important parameter concerning the applications of nanoliposomes (NLs) in manufacturing, such as the food, cosmetic and pharmaceutical industries, since the viability of the usage of NLs to protect the activity of targeted molecules and control their release depends on it. In this work, the physical stability of reduced glutathione (GSH) loaded NLs (Lip), mono-layer chitosan coated Lip (CTS-Lip) and double-layer alginate-chitosan coated Lip (ALG-CTS-Lip) in different conditions was characterized by the changes of the average particle sizes, zeta potentials, and leakages of the encapsulated GSH. It was revealed that pH had a negligible influence on Lip but induced significant changes in the mean particle sizes of CTS-Lip and ALG-CTSLip, which was inferred to relate to the solubility of ALG and CTS at different pH values. In the case of metal ions, Mg2+ showed some influence on Lip and CTS-Lip while Zn2+ and Ca2+ usually used as crosslinker exhibited significant impact on CTS-Lip and ALG-CTS-Lip. According to the release rates of GSH and the changes of particle size, ALG-CTS-Lip were the most stable sample over a wide range of temperature (20-100 degrees C) and a long time of storage (60 days). Moreover, CTS monolayer and ALG-CTS double layer coating on the surface of NLs significantly enhanced the thermal stability of NLs and reduced its disintegration in simulated intestinal fluid (SIF). Therefore, surface coating could induce different effects on the physical stability of NLs under different environments. These results may to some extent facilitate the rational design of novel NL-based delivery systems used in manufacturing.