Interaction between a monosaccharide and a phospholipid molecular layer

Formation of lipid tubules induced by a sugar-like molecule myo-inositol

The sugar-like molecule myo-inositol (InOH) bears an uncanny structural resemblance to the pyranose form of the sugar D-glucose (DG). InOH and its derivatives play a pivotal role in cell biology; whereby its interaction with the model membrane needs to be studied. Here, we have demonstrated that lipid tubules are formed as a result of the above-said interactions and that these interactions can be prevented by using hydroxyl protected InOH derivatives. We have tried to elucidate the nature of the InOH-membrane interactions by comparing them with DG-membrane interactions and have proposed a mechanism for the same.

Polyoxyethylene/polyoxypropylene dimethyl ether (EPDME) random copolymer improves lipid structural ordering in stratum corneum of an epidermal-equivalent model as seen by two-photon microscopy

BACKGROUND/PURPOSE

Topical application of polyoxyethylene/polyoxypropylene dimethyl ether (EPDME) random copolymer improves the barrier function of skin, whereas polyethylene glycol (PEG) and polypropylene glycol (PPG) are ineffective. The aim of this work was to examine the interaction between these polymers and lipid molecules in the stratum corneum in order to establish whether EPDME-specific changes in the structural ordering of lipids might account for the improvement of barrier function.

METHODS

We used two-photon microscopy to evaluate the effects of EPDME, PEG, and PPG on the structural ordering of lipids in an epidermal-equivalent model in terms of the fluorescence changes of Laurdan, a fluorescent dye that responds to changes of membrane fluidity. The generalized polarization (GP) value, a parameter that reflects lipid ordering, was measured at various depths from the surface of the stratum corneum.

RESULTS

EPDME increased the GP value to a depth of about 3 µm from the surface, indicating that lipid ordering was increased in this region, while PEG and PPG of the same molecular weight had no effect. Diffusion of Lucifer yellow into the epidermis was reduced after application of EPDME, indicating that the barrier function was improved.

CONCLUSION

These results support the view that EPDME improves barrier function by increasing the ordering of lipid structures in the stratum corneum. The methodology described here could be useful for screening new compounds that would improve the structural ordering of lipids.

Characteristic responses of a phospholipid molecular layer to polyols

Polyols (sugar alcohols) are widely used in foods, pharmaceutical formulations and cosmetics, and therefore it is important to understand their effects on cell membranes and skin. To address this issue, we examined the effect of polyols (1,2-ethanediol (ethylene glycol), 1,3-butanediol, 1,2,3-propanetriol (glycerol), and 1,2,3,4-butanetetraol) on artificial membrane systems (liposomes, monolayers, or dry films) prepared from phospholipid (1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)). 1,2-Ethanediol and 1,3-butanediol had little effect on the size of the DMPC liposomes or the surface pressure (π)-surface area (A) isotherm of DMPC monolayers at an air-water interface, whereas 1,2,3-propanetriol or 1,2,3,4-butanetetraol increased both liposome size and surface pressure. Attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) and differential scanning calorimetry (DSC) were used to evaluate the interaction between DMPC and polyols. These experimental results suggest that the chemical structure of polyol plays an important role in the characteristic interaction between polyol and DMPC.

Dynamical formation of lipid bilayer vesicles from lipid-coated droplets across a planar monolayer at an oil/water interface

Recently, the transfer method has been shown to be useful for preparing cell-sized phospholipid bilayer vesicles, within which desired substances at desired concentrations can be encapsulated, with a desired asymmetric lipid composition. Here, we investigated the transfer process of water-in-oil (W/O) droplets coated by phospholipid monolayers across an oil/water interface by both experimental observation and theoretical modeling. Real-time experimental observation of the transfer revealed that the transfer process is characterized by three kinetic regimes: a precontact process (approaching regime), an early fast process (entering regime), and a late slow process (relaxation regime). In addition, bigger droplets require much more time to transfer than smaller droplets. We propose a theoretical model to interpret this kinetic process. Our theoretical model reproduces the essential aspects of the transfer kinetics, including its size-dependence.