Eugenol encapsulation into conventional liposomes and chitosan-coated liposomes: A comparative study

The aim of this study is to investigate the effect of chitosan coating layer and molecular weight on the characteristics of liposomes encapsulating eugenol, a volatile essential oil component. Two approaches were used: eugenol-loaded conventional liposomes were prepared and then coated with chitosan (referred to as chitosan-coated liposomes or chitosomes), blank empty chitosomes were prepared and then eugenol was added to join the structures (referred to as preformed chitosomes). Eugenol-loaded liposomes and -chitosomes were characterized and compared in terms of size, eugenol encapsulation efficiency (EE), eugenol loading rate (LR), and phospholipid and cholesterol incorporation rates (IR). Compared to conventional liposomes, the presence of chitosan coating layer increased significantly the mean particle size in a concentration dependent manner. Increasing the chitosan molecular weight led to an increase in cholesterol incorporation in liposomes. High EE of eugenol was obtained in all formulations (above 68.8%). However, both phospholipid and eugenol incorporation rates decreased in chitosomes. All chitosomal formulations enhanced the antioxidant activity of eugenol compared to the uncoated ones and maintained the eugenol encapsulation after 2 months of storage at 4 °C. The retention efficiency (RE) of eugenol into preformed blank conventional liposomes and chitosomes was assessed using the dialysis technique. After 21 days, the RE of eugenol reached 41, 45.5 and 80%, respectively in preformed liposomes and preformed chitosomes with low and high molecular weight. The results have demonstrated the incorporation of eugenol into both preformed systems, with the ability of chitosan to enhance its incorporation, especially with the highest molecular weight.