Monosaccharides driving the formation of conjugated linoleic acid vesicles in near-neutral solutions via weak noncovalent bonding interactions

Abstract

Acted as the second component of fatty acid vesicles (FAV), almost all reported chemicals except for bio-incompatible cationic amphiphiles caused a one-side pH window extension of FAV whilst the other-side shrinkage accordingly. We recently found that dodecanol could partially compensate the alkaline-side pH window shrinkage of FAV when the acidic-side was extended by sodium dodecylsulfate (SDS). Therefore, we guess that if one single small molecule played two − in − one function as both SDS and dodecanol done on the different-side pH window, it might cause a two-side pH window extension of FAV entering into near-neutral pH. Taking conjugated linoleic acid (CLA) as the model fatty acid, ribose, glucose, glucosamine and acetyl glucosamine as the models of the second component, the influence on the pH window extension for the FAV of CLA by each of the monosaccharides and the involved noncovalent bonding interactions are investigated by laser Tyndall effect, pH titrimetry, transmission electron microscopy, dynamic light scattering, ultraviolet absorbency, isothermal titration calorimetry measurement and binding energy calculation. The two-side pH window extension for the FAV of CLA is realized by aid of the two − in − one function of monosaccharides that create H-bonding interaction with the FAV surface and thus enhancing hydrophobic self-assembly of CLA. It is crucial for self-assembling FAV as primitive cell membranes and applying it as modern nutrient carriers or drug delivery systems in the physiological pH range. We propose a practical microenvironmental polarity criterion based on the experimental results to predict how the second component to extend the pH window of FAV: If the second component made the FAV surface more hydrophobic on the alkaline-side pH window while more hydrophilic on the acidic-side via molecular interactions, it could drive the corresponding-side pH window extension, otherwise the corresponding-side pH window shrinkage.