TLC characterization of liposomes containing D-myo-inositol derivatives

The thin-layer chromatographic (TLC) behaviour of liposomes containing inositol phosphates (IPs) was studied. The liposomes contained different concentrations of D-myo-inositol 1,4,5k-trisphosphate (IP3), D-myo-inositol 1,2,6-trisphosphate (alpha-trinositol, PP 56, a novel Perstorp Pharma derivative), D-myo-inositol 1,3,4,5-tetrakisphosphate (IP4), D-myo-inositol 1,3,4,5,6-pentakisphosphate (IP5) and D-myo-inositol 1,2,3,4,5,6-hexakisphosphate (IP6). Migration of all liposome batches was compared to that of control liposomes (containing only triple distilled water), and to that of free phosphatidylcholine (PC); the same amount of lipid was used in all situations. Thin-layer chromatography was performed on silica gel as adsorbent. As solvent we used an n-buthanol:ethanol:water mixture in a 4:3:3 volume ratio. Significant differences were found between PC and all liposome batches, as well as between control liposomes and the ones containing IP3, alpha-trinositol, IP4, or IP5, in various concentrations. Liposomes containing IP6 migrate completely differently compared not only to phosphatidylcholine and control liposomes, but also to the ones containing other IPs ( < 10(-3) M). Unlike the other IPs studied, liposome-entrapped IP6 elicits dose-dependent contractions of the isolated rat aorta. This suggests that liposomes loaded with IP6 undergo, during or after their preparation, physico-chemical alterations that eventually change their drug-delivery capacity.