2003 年 63 巻 2 号 p. 79-88
In order to develop an intravenous formulation of all-trans retinal (vitamin A aldehyde, VAA) for the treatment of night blindness, VAA and dipalmitoylphosphatidylcholine (DPPC) were sonicated and dispersions in the VAA mole fraction range of 0.1-0.7 were stable at room temperature for 3 days. In order to clarify the dispersal mechanism, the interaction between VAA and DPPC was investigated using several physicochemical techniques. Dynamic light scattering measurements showed that the diameter of the dispersed particles was 50-70 nm. A limited amount of VAA was incorporated into DPPC bilayer membranes (approximately 5 mole%). The trapped aqueous space marker calcein and the volume in the VAA/DPPC particles was decreased remarkably into small unilamellar vesicles of DPPC with the addition of VAA. The decline in the fraction of vesicular particles was also confirmed by fluorescence quenching of N-dansylhexadecylamine in the DPPC membrane by the addition of the quencher CuSO4. These results indicate that the excess VAA separated from the DPPC bilayers was stabilized as suspension particles by the DPPC surface monolayer. The monolayerbilayer equilibrium of VAA/DPPC mixtures was explored by measurements of spreading and collapse pressures.
