Stability evaluation of interdigitated liposomes prepared with a combination of 1,2-distearoyl-sn-glycero-3-phosphocholine and 1,2-dilauroyl-sn-glycero-3-phosphocholine

BACKGROUND: In order to obtain small and homogenous liposomes encapsulating gallic acid (GA) with interdigitated leaflets, a combination of phosphatidylcholine (PC) of medium length sn-1 and sn-2 acyl chains with PC of longer acyl chains at both sn1 and sn2 positions were employed. Four formulations respectively consisting of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC); DSPC/1,2-dilauroyl-sn-glycero-3-phosphocholine (DSPC/DLPC) (1:1, mol mol⁻¹); DSPC/DLPC (3:1, mol mol⁻¹) and Lipoid S75, were prepared. For each formulation, the stability of liposomes during storage was investigated. RESULTS: The initial size of liposomes ranged from 36.61 ± 0.61 to 125.43 ± 2.15 nm and their polydispersity index (PDI) from 0.14 ± 0.01 to 0.28 ± 0.01. The formulations combining DSPC and DLPC resulted in very stable liposomes physically, during up to 84 days of storage with no significant change in both size and PDI except a slight increase in the size at the 42nd day. The molecular state of the bilayers and their thermal behavior as given by FTIR and Differential Scanning Calorimetry (DSC) results supported the hypothesis of an interdigitated state of the liposomes formed by DSPC/DLPC combination at a molar ratio of 3:1. CONCLUSION: Interdigitated liposomes composed of two symmetric phospholipids (DSPC and DLPC) were obtained for the first time and exhibited a good stability during storage in solution.