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The thin-layer chromatographic (TLC) behaviour of small unilamellar liposomes containing inositol phosphates (IPs) was studied. The vesicles contained different concentrations of D-myo-inositol 1,4,5-triphosphate (IP3), D-myo-inositol 1,2,6-triphosphate (alpha-trinositol, PP 56, a novel Perstorp Pharma derivative), D-myo-inositol 1,3,4,5-tetraphosphate (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 (multilamellar and small unilamellar, both 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 with silica gel as adsorbent. The developing solvent was an n-buthanol:ethanol:water mixture in a 4:3:3 volume ratio. At doses higher than 10(-2) M liposomes containing alpha-trinositol and IP6 had a different migration than PC, MLV or SUV as well as all batches of liposomes. Physiological studies (using as model endothelized rat aorta rings) proved that in this situation they had no effects.

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.

One of the most important problems for the use of liposomes as a drug delivery system is the modification of the vesicle induced by the liquid medium in which they are introduced (blood plasma for in vivo studies and the saline buffer solution for in vitro studies). Using thin-layer chromatography (TLC) we compared the behaviour of phosphatidylcholine (used for liposomes preparation) to that of the following unfilled liposomes: multilamellar liposomes (MLV); small unilamellar vesicles (SUV); and reverse phase evaporation vesicles (REV), before and after storage for 15 min in Krebs-Henseleit solution (37 degrees C, pH 7.4, aerated continuously with 95% O2 + 5% CO2). All variants contained the same amount of phosphatidylcholine. Thin-layer chromatography was performed on silica gel 60 as adsorbent. Two types of solvents were tested: one based on chloroform/alcohol (n-butanol or n-propanol or methanol)/water mixture (in different ratios) and another based on alcohol/alcohol/water mixture (n-butanol/n-propanol/water in 4/3/3 volume ratio). In all variants of chloroform containing solvents no differences were found between phosphatidylcholine and all types of liposomes. When using as solvent n-butanol/n-propanol/water significant differences were found between all types of liposomes before and after storage in Krebs-Henseleit solution. Their presence, after TLC treatment, was shown in electron microscopy studies.