Preparation of sodium hyaluronate coated liposomes: effect of polymer molecular weight, coating concentration, amount of charged lipids and type of hydration medium on the stability

In this study, liposomes consisting of soybean phosphatidyl choline (SoyPC) and different molar concentrations (10 mol% and 20 mol%) of dioleoyl trimethylammoniumpropane (DOTAP) were prepared by the thin film hydration method and coated with sodium hyaluronate (NaHA) of different MWs (8-15 kDa, 30-50 kDa and 90-130 kDa) and concentrations (0.01-0.2% w/w) using phosphate buffer (PB) or glycerol phosphate buffer (G-PB) as the hydration medium. These NaHA coated liposomes could have a potential in the treatment of dry mouth since glycerol and NaHA are known for their lubricating and hydrating properties. The liposomes composed of SoyPC-DOTAP 20 mol%, and coated with NaHA MW 90-130 kDa, 0.05% w/w were found to be most stable during storage. The liposomes with 20 mol% DOTAP coated with NaHA MW 30-50 kDa, 0.05% w/w showed promising results as these stayed stable for at least two weeks. However, the liposomes coated with NaHA MW 8-15 kDa were generally unstable irrespective of the combinations of the investigated parameters. When the stable liposomes were introduced into artificial saliva (AS), aggregation rapidly occurred. Sodium alginate (NaAlg) coated liposomes that were prepared for comparison were found to be stable in AS. The study has demonstrated the influence of the amount of charged lipid which must be high, the polymer MW which must lay in the area 30 kDa-130 kDa and coating concentration which should be intermediate 0.05% w/w in preparing stable NaHA coated liposomes. Further studies need to be conducted to understand the instability exhibited by the NaHA coated liposomes in AS.